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Engine Specific Info and Questions => IDI Engine => Topic started by: 92EcoDiesel Jetta on January 24, 2013, 08:07:11 pm

Title: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 24, 2013, 08:07:11 pm
Last night in 12F ambient, driving on the hwy for an hour I was getting lukewarm heat. Last winter I had great heat.

92 Eco with AC.

I pulled over at a rest stop and noted the following:

1. Coolant temp gauge in the middle

2. Upper rad hose hot, 180F per IR thermometer

3. Lower rad hose cold

4. Upper part of radiator fins hot

5. Bottom of radiator fins cold

6. heater core hose in hot, 180F per IR thermometer

7. heater core hose out hot, 160F per IR thermometer

I think all of the above is normal for 12 F ambient and the thermostat and heater core is OK.

Why am I getting lukewarm heat?

Per the Bently, the amount of heat is controlled by blend door. I assume it blends the ratio of cold fresh air vs hot air from the heater core? Am I getting too much cold air because the blend door is out of adjustment or can it be a vacuum problem to the servos?

I don't want to rip the dash apart to find where the problem is. Is the blend door cable on the heater box accesible without ripping the dash apart? Maybe it's just a matter of adjusting it?
Title: Re: Luke warm heat 92 Eco
Post by: cyrus #1 on January 24, 2013, 08:11:43 pm
I think you are on the right track with the blend door theory.  You should see more of a temperature drop than 20° across the heater core.  Something must be causing a lack of air flow through the heater core.

The other thing that happens in MKII's is the foam that seals the blend doors tends to disintegrate over time.  Have you had any black bits come through the vents?
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on January 24, 2013, 08:12:44 pm
you probably need to re-foam your heater box..

i would be willing to bet that all the foam has fallen off your blend doors..

its a real bugger to pull the dash and heater box just to re-seal the blend doors..

and you might as well replace the heater core while you are in there, because they are cheap, and it takes another 5 minutes..
Title: Re: Luke warm heat 92 Eco
Post by: mystery3 on January 24, 2013, 08:13:42 pm
Something must be causing a lack of air flow through the heater core.

All the foam that used to be on the blend door?
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 24, 2013, 08:20:07 pm
Bits of foam has been coming out of the vents for the last 3 years. What if I close off the fresh air inlet under the rain tray? Will that work as a temporary measure to get more heat by blocking out cold air coming in? It's easy enough so I'll try it.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 24, 2013, 08:28:06 pm
First I would check the blend doors. They can be re-covered in-situ with good tape (metallic, gorilla... not crap duct tape).  I take out the center vents and the console... the front duct can then be extracted. There are a couple of screws on the bottom of the dash that come out to flex the dash a bit.

(https://lh6.googleusercontent.com/-aIsCdeRc7yQ/UQIJnPAHcYI/AAAAAAAAA7I/_p0O1tg1CY4/s640/ventDoors_sansFoam-IMG_0743.jpg)



I would not cover the fresh air inlet. Recirc will only cause major fogging of the glass. (You can always tell the guy on the highway with re-circ active, lol.)

I did the blend doors in my 89 and the heat still sucks. The core must be plugged.  Pulling the airbox is a PITA. I have heard guys have split the evap section off and removed just the heater section, but that can't be any fun either.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 24, 2013, 08:39:13 pm
Thanks Tyler! Were those round holes in the blend door once covered in foam and they need to be recovered? I guess I don't understand how the blend doors work.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 24, 2013, 08:42:22 pm
Why didn't VW use a solid piece of metal instead of swiss cheesing it with big holes???
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 24, 2013, 08:54:18 pm
This is a hacked photo (not my original pic) showing airflow in the heat section.

Blue= cold air
Red = hot air
Purple = blended air
Yellow = door movement & core

(https://lh6.googleusercontent.com/-2qQ-iUJb8gc/UQIOjrXBzFI/AAAAAAAAA7Y/OOtGC-sS3wk/s640/ventDoors_withFoam-IMG_0743-ALT.jpg)

The door closer to the firewall directs air to and/or around the core for temperature adjustment.

The door near the front directs the blended air the the vents or to the flapper on the left.

The flapper on the left directs up to glass or down to feet.
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on January 25, 2013, 10:23:42 am
the heater core CANT be blocked with foam, because the foam is AFTER the core, thats why you see it blowing out the vents..
Title: Re: Luke warm heat 92 Eco
Post by: srgtlord on January 25, 2013, 11:27:43 am
As for the swiss cheese... I bet it saved VW a nice chunk of change for not having to put the extra metal in.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 25, 2013, 12:26:07 pm
the heater core CANT be blocked with foam, because the foam is AFTER the core, thats why you see it blowing out the vents..
Hmmm... when the door is blocking the core for cold operation, it must be before the core, so loose foam could get blown into the fins.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 25, 2013, 02:18:02 pm
92 ecojetta: That infrared thermometer sounds like a nice diagnostic tool. Could you post a bit about it.

TylerD: I can separate the back of the heater from the inside of the car without taking out the dash? I think it was mentioned in another thread yesterday or the day before. What approximate angle was the flow diagram taken from?

Thanks guys.
Title: Re: Luke warm heat 92 Eco
Post by: 8v-of-fury on January 25, 2013, 02:44:42 pm
Just your basic IR thermometer.

(http://i299.photobucket.com/albums/mm307/J_holubek/20130125_173153.jpg)
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 25, 2013, 02:51:24 pm
Jeremy:
Looks pretty cashy. Must be a pretty common tool then?
Title: Re: Luke warm heat 92 Eco
Post by: 8v-of-fury on January 25, 2013, 02:57:07 pm
I think they can be had for under $50. OR close to it, a very very useful tool! I use it in brewing too ;)
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 25, 2013, 03:05:44 pm
You can buy an IR thermometer from HF (where mine is from) or Radio Shack. Everybody sells one just about.

I dug out my spare heater/AC box from the 91 Eco parts car and studied its operation a bit. The blend door is the one with 10 holes closest to the firewall. The one with 3 holes is not called a blend door I don't think.

There is no foam on the blend door or the 3 hole door. Was the holes supposed to be covered by foam? Why put the holes there in the first place if when the foam falls off, it stops working as a blend door? WTF? Someone please explain why VW did that!
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 25, 2013, 03:41:02 pm
The design envelope was probably 10-15 yrs.

The flow image is from not quite overhead.

Here is an overhead sketch of the heater section & core.

Core is yellow, doors are black and pivot on the circles.
(https://lh4.googleusercontent.com/-IeUPbwI4sxQ/UQMVU7YZPcI/AAAAAAAAA8o/iAhgNeM41wk/s640/Copy%2520of%2520Airbox-top.jpg)
Doors are shown full-cold, vents only.
Dashed lines indicate doors in full-hot, def/floor


I have heard of masochistic folks getting the airbox out without the dash, but hoooooo..... can't be easy.

One note about taping the doors: I added 6mm tape overhangs, like door-sweeps, since the metal doors are slightly smaller than the openings.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 25, 2013, 04:14:45 pm
Thanks much for the detailed diagram.
I am pretty sure that the problem in my car is mainly in that top door. Perhaps it is holey. Is the top door controlled by the slide lever for heat?

The heater gets warmer when the the heat lever is over at hot.

I can feel the bottom door vacuum solenoid moving when I adjust it. But the panel vents are always blowing hard and the top and bottom vents are fairly weak.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 25, 2013, 04:27:41 pm
Yeah, the temp-blend door is controlled the cable.  (I wish they were all cable control, like the Audi 90 & Audi Cabriolet. )

The core adds a bit of restriction, so if you don't have a noticeable air-volume drop when full-hot, the door foam is likely shot.

Constant dash flow would indicate bad foam on the front door.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 25, 2013, 05:08:54 pm
Thanks for letting me learn more about the operation of the heater. Hope that the original poster is ok with it.
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on January 25, 2013, 05:34:37 pm
Jeremy:
Looks pretty cashy. Must be a pretty common tool then?

CHEAP...

BTW, only the non-a/c cars had a cable that controlled the blend door position..

the a/c cars were vacuum controlled..
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 25, 2013, 05:52:30 pm
 

BTW, only the non-a/c cars had a cable that controlled the blend door position.. the a/c cars were vacuum controlled..


Mk1, MK2 AC has vac-control on outlets (dash, def., etc), but temp is cable.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 25, 2013, 05:55:31 pm
Mine is an ex AC car. What does the heat cable do?
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on January 25, 2013, 06:07:25 pm
I think they can be had for under $50. OR close to it, a very very useful tool! I use it in brewing too ;)

just bought one at Sears for $22..
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 25, 2013, 06:16:53 pm
Mine is an ex AC car. What does the heat cable do?

The cable swings the door to send air through or around the core.

Pic of the bottom of the airbox:
(https://lh4.googleusercontent.com/-UCNY9ERHPh8/UQM7Bla-a9I/AAAAAAAAA9M/fTFPO-EIktg/s800/IMG_9225.JPG)

The dash ducts are on the far left. The footwell duct has the angled edge.

The vacuum dashpot on the bottom controls the selection of dash vents or footwell/defrost - the blue cable controls the temperature door.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 25, 2013, 06:30:05 pm
I can see that solenoid move when I switch positions with the bottom control. Also the cable is moving something. I can feel the drag in the cable pulling and pushing something. There seems to be a lot of air pressure that leaks hot or at least warm air in the seal that is covering the passenger compartment side near the bottom. Are there are any more ideas before just ripping into it?
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 25, 2013, 06:53:42 pm
Here is the thread I ripped a pic from. He cut off the AC lines to get the whole airbox out while the dash remained. (some pix missing)
http://forums.vwvortex.com/showthread.php?2355434-Heater-Core-Time

Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 26, 2013, 09:56:39 am
The design envelope was probably 10-15 yrs.


So VW purposely put holes in the doors, covered them with foam that lasts 15 years then fall apart. Sweet! All they had to do was use a door with no holes, and we wouldn't be having these problems.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 26, 2013, 10:24:04 am
Gotta reduce weight everywhere... these are performance machines, doncha-know.  :P


Seriously, somebody must have had a reason, even half-baked. Beats me.
Title: Re: Luke warm heat 92 Eco
Post by: air-cooled or diesel on January 26, 2013, 11:16:24 am
the foot duct also has 2 large passages blowing toward rear cabin, i taped these also, usually has crumbling foam sealing these too.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 27, 2013, 11:28:45 am


I would not cover the fresh air inlet. Recirc will only cause major fogging of the glass. (You can always tell the guy on the highway with re-circ active, lol.)


I think I found the multi issues that is causing lukewarm heat. Previous to this, I used to marvel at how fast the heat would come on, literally within minutes of starting a cold engine I would feel warm air coming out the vents before the coolant temp gauge even moves, and it would get toasty hot when the gauge is in the middle. Now I get only lukewarm heat driving for hours.

The problem in a nutshell is the fresh air/ recirc door is always in fresh air mode and the blend door foam is gone letting cold fresh air through all the time.

I dug out my spare hvac box and studied it's operation. The door on the right (no holes) is the fresh air/recirc door. It has no foam because it is a solid door. The blend door and the vent door have big holes covered in foam and when the foam deteriorates the doors don't do it's job anymore and let cold air through.

I pulled the rain tray and look in the fresh air inlet where the door is clearly visible. Moving the control head levers through all its positions did not move the fresh/recir door (defaults to fresh cold air). I then hooked up a Mityvac to the vacuum servo for the fresh air door and can move it no problems so the problem is probably in the control head vacuum switch or the vacuum line to the servo. I can hear vacuum as I move the control head lever so the control head is getting vacuum from the reservoir.

I just went for a test drive with the Mityvac hooked up to the fresh air/ recirc servo with the door closed (in recirc mode) and got warm air within minutes of a cold engine start, back to how it used to be, i.e. great heat.

I am not gonna pull the dash apart to fix the blend door for now and will try to either block off the fresh air inlet under the rain tray or wire closed the fresh air door.

(http://i1183.photobucket.com/albums/x480/Ecodiesel92/IMG_20130126_190958.jpg)
Title: Re: Luke warm heat 92 Eco
Post by: air-cooled or diesel on January 27, 2013, 12:22:09 pm
right there you can easily get to and tape blend door. open vent door to vent pos, in back of that you now have a direct path to blend door. taping both doors,,, real good. if you get to vent door, do both; 1 side.
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on January 27, 2013, 05:58:11 pm


I would not cover the fresh air inlet. Recirc will only cause major fogging of the glass. (You can always tell the guy on the highway with re-circ active, lol.)


I think I found the multi issues that is causing lukewarm heat. Previous to this, I used to marvel at how fast the heat would come on, literally within minutes of starting a cold engine I would feel warm air coming out the vents before the coolant temp gauge even moves, and it would get toasty hot when the gauge is in the middle. Now I get only lukewarm heat driving for hours.

The problem in a nutshell is the fresh air/ recirc door is always in fresh air mode and the blend door foam is gone letting cold fresh air through all the time.

I dug out my spare hvac box and studied it's operation. The door on the right (no holes) is the fresh air/recirc door. It has no foam because it is a solid door. The blend door and the vent door have big holes covered in foam and when the foam deteriorates the doors don't do it's job anymore and let cold air through.

I pulled the rain tray and look in the fresh air inlet where the door is clearly visible. Moving the control head levers through all its positions did not move the fresh/recir door (defaults to fresh cold air). I then hooked up a Mityvac to the vacuum servo for the fresh air door and can move it no problems so the problem is probably in the control head vacuum switch or the vacuum line to the servo. I can hear vacuum as I move the control head lever so the control head is getting vacuum from the reservoir.

I just went for a test drive with the Mityvac hooked up to the fresh air/ recirc servo with the door closed (in recirc mode) and got warm air within minutes of a cold engine start, back to how it used to be, i.e. great heat.

I am not gonna pull the dash apart to fix the blend door for now and will try to either block off the fresh air inlet under the rain tray or wire closed the fresh air door.

(http://i1183.photobucket.com/albums/x480/Ecodiesel92/IMG_20130126_190958.jpg)

MK2s dont technically have a RECIRC function tho?
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 27, 2013, 06:11:37 pm
MK2s dont technically have a RECIRC function tho?

It's automatic when the selector is moved to the AC positions - the fresh/recirc door swings to draw air from the cabin. (In DEF mode, the door stays in fresh position, but the compressor and radiator fan kick on.)


@92Eco:

It is not very hard to put tape on the blend doors while the airbox is in the car. Much better solution than recirculating moist air.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 27, 2013, 06:33:37 pm
MK2s dont technically have a RECIRC function tho?

It's automatic when the selector is moved to the AC positions - the fresh/recirc door swings to draw air from the cabin. (In DEF mode, the door stays in fresh position, but the compressor and radiator fan kick on.)


@92Eco:

It is not very hard to put tape on the blend doors while the airbox is in the car. Much better solution than recirculating moist air.

I have a spare heater box on the bench and I can see that the vent door only opens part way such that I cannot get my hand in there to access the blend door to tape up the holes. To remove the vent door to get better access would require splitting the box in half and that requires pulling the box. I can probably use small pieces of tape to cover the holes individually using long nose pliers . But the 7 inline holes in the blend door (pic taken from Vortex) is not accessiblt via the vent door andthe box must be split apart.

Recirculating moist air is not a problem if I open the windows when needed. The way it was, I was not getting enough heat to melt snow on the windshield.

(http://i11.photobucket.com/albums/a186/garysdrumz/IMG_0793.jpg)
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 27, 2013, 07:00:11 pm
I used a small quick-clamp to hold the vent door open while I taped the blend door.

(https://lh6.googleusercontent.com/-ok_x0eXC814/TyMf1I4yiPI/AAAAAAAAAhI/Ic4FsPUs8Wc/s640/IMG_8971_med.jpg)


It does help to have small hands.  :-\
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 27, 2013, 07:37:04 pm
Just looked at my spare box again. By forcing the vent door open more than it does, I can barely get my hand in there and touch the blend door. The vacuum servo in your pic that that you have the clamp on, on mine it has 2 vacuum tubes, one is yellow, the other is green. The yellow open the vent door, the green I can see it tries to pull the rod in when I apply vacuum but does not do anything to the vent door. What does it do on yours?
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 27, 2013, 08:19:39 pm
My spare behaves similarly: the port on the end pulls the rod in, the one on the side of the servo seems to pull somewhat, but not directly back like the end port does.

A post on the 'tex describes the routing, but the pix are gone. http://forums.vwvortex.com/showthread.php?2883746
Title: Re: Luke warm heat 92 Eco
Post by: air-cooled or diesel on January 28, 2013, 08:26:36 am
dont force either door, if you put vent selector to dash vents, if you have vacuum servo for dash control you may need to make some vac, turn car on and vent door should be in fully open position. it will close chamber that goes to floor and defrost. then you can see blend door in back of vent door.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 28, 2013, 01:21:02 pm
There is no good reason to run the engine, when the dashpot can be manually retracted to hold the door open for service.  ::)
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on January 31, 2013, 08:38:36 am
I've had a cold and was not motivated to work on sealing the blend door. Feel a little better now and got the console out but stuck at this pic.

(http://i11.photobucket.com/albums/a186/garysdrumz/IMG_0735.jpg)

The Vortex thread where I got this pic from was totally not clear on how to get this cover off along with the center dash vent. On mine, I think there are staples holding the dash vent in (Vortex thread did not mention that). Also Does the dash mounting hardware have to be taken out to move it upwards and out of the way for clearance?
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 31, 2013, 08:58:54 am
The control assembly does not need to be unfastened, but it may help to remove the radio, to see the ductwork leading to the side vents.

The frame for the center outlets has two screws inside the top edge and it has barbed tabs. I use small screwdriver to gently pry the barbed tabs while working the frame out, one edge at a time: top edge a bit, bottom a bit, top a bit, etc. It will pull straight out and leave the flexy sections of duct attached to the plenum.

Does this MK2 have the knee-rail? It will need to come out, if it ain't out already.

The plenum can be unfastened by the two plastic nuts on either side. Then the plenum can be pulled away enough to clear the studs and worked down and out. It will be pulled out of the side-ducts.

It may be helpful to unfasten the hex-head machine screws that attach the lower edge of the dash to the framework - there is one on each side of the plenum, usually hidden by the plastic panels under the dash (driver side has the pocket for the owner's manual, passenger side has the small tray). Then the bottom edge of the dash can be flexed for more clearance.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on January 31, 2013, 09:08:58 am
My car puts out a fair amount of heat but not much volume in the crack that those fingers are in. Once I can get my car back into the shop I am going to see if I can pry into it and get those doors fixed.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on January 31, 2013, 09:13:35 am
It may be helpful to unfasten the hex-head machine screws that attach the lower edge of the dash to the framework - there is one on each side of the plenum, usually hidden by the plastic panels under the dash (driver side has the pocket for the owner's manual, passenger side has the small tray). Then the bottom edge of the dash can be flexed for more clearance.

Those panels are on the versions without the knee rail... the knee-rail probably hides those screws on the knee-rail version.

Edit: yeah, on the ECO, the knee rail hides the right-side screw, the left is visible close to the ignition switch.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 01, 2013, 02:32:47 pm
I got the cover separated from the center dash vent. Problem was the plastic was too cold and stiff. I heated it with a hair dryer and after some twisting it separated. The blend door foam was 90% gone. The foam is only on one side of the blend door (blower side). There is no sign of any foam on the vent door (the front one). Is the vent door foamed from the factory? The way mine look and feel, I'd say it was not covered.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 01, 2013, 07:58:45 pm
Yeah. Both sides were originally covered, on both doors.

The optimum is to cover both sides, but just one side should be sufficient to route most of the flow the desired direction. As I noted earlier, a 1/4" overhang of cover can help seal around the perimeter of the doors when fully open or closed.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 04, 2013, 01:13:15 pm
Got both the blend door and vent door covered today! I used aluminum duct tape in mutiple small pieces and snuck them on by hand. It should last much longer than the foam crap! What a difference! I can't keep my hand at the heat coming out the vent door, it is that hot!

Thanks for all the help!

(http://i1183.photobucket.com/albums/x480/Ecodiesel92/IMG_20130204_150046_zpsb73f044b.jpg)
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on February 04, 2013, 01:58:53 pm
I have been planning on refurbishing the heater system on my vw too. That sounds like an excellent way of recovering them. I have used on heating ducts and has very tenacious glue. Thanks for sharing. 

Did you cover both sides so that the glue layers are touching?
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 04, 2013, 02:42:32 pm
It is impossible do do both sides unless the heater box is removed from the car and disassembled to get the doors out.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 04, 2013, 05:47:23 pm
Not impossible to do, if you have the dexterity of a surgeon... or are a glutton for punishment. But not really needed, if good tape is used.

The PO of my '89 used crappy masking tape on one side only.  ::)

Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 04, 2013, 05:53:23 pm
Getting the plenum back can be a chore, tho... that is, getting the ducts for the outer vents to connect to the plenum as it's going back into place. That's when having the radio out to get another hand in there to guide the pieces together can help. If needed, the control lever bits can be unfastened and pulled forward some.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 04, 2013, 06:13:19 pm
Getting the plenum back can be a chore, tho... that is, getting the ducts for the outer vents to connect to the plenum as it's going back into place. That's when having the radio out to get another hand in there to guide the pieces together can help. If needed, the control lever bits can be unfastened and pulled forward some.

I plan on leaving all the pieces taken off as is till it's warmer (spring). Rebuild the doors of my spare heater box over the winter and do a swap spring time. I have a crack free dash that I can install then also. Plus I may think about getting the AC working since I have all the parts from the 60K Eco parts parts.

While the dash was apart, I got the cluster out and undid the mod on the tach which was previously converted to a mag pickup and made it a W terminal. The mag pickup worked fine, it's the trigger magnets that keeps flying off that was a PITA. I am glad to get rid of all that junk by the crank pulley, which was in the way changing belts.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 04, 2013, 07:26:39 pm
10-4. When I took apart my ECO engine, I found loose magnets stuck to the block behind the timing belt cover.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 05, 2013, 10:53:00 am
10-4. When I took apart my ECO engine, I found loose magnets stuck to the block behind the timing belt cover.

I know where my magnets are from, but where are yours from? I don't think there are that many mag pickup tachs out there that uses magnets.

My heat is working great again. From a dead cold start, I drive for 5 blocks and I have warm air coming out the ducts with the temp gauge still dead cold.
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 05, 2013, 11:14:40 am
I know where my magnets are from, but where are yours from? I don't think there are that many mag pickup tachs out there that uses magnets.

I don't know where from (they were on the engine when I got it), but they had little spiked feet to grip onto stuff.
Title: Re: Luke warm heat 92 Eco
Post by: scrounger on February 05, 2013, 11:33:36 am
I went over to my neighborhood Ace and they had the metal tape with diagonal fiberglass fibers in it for strength and they also had one with a bit of insulation in it. Still too cold to take the dash and ductwork out but I think I am going to use the tape with the diagonal fibers in it.
92 eco diesel and others thanks.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 10, 2013, 02:22:48 pm
After taping up the blend doors and have excellent heat again, I took it for an hour long drive today. Not as cold (25F) as the last drive (12F) but I had great heat. Had to lower the heat lever to a little past middle. If I put it on max, it'd be too hot.\

At the rest stop I observed the following:
Uppper Rad hose 180 F per IR thermometer
Lower Rad hose cold per my fingers
Heater core hose in 180F per IR thermometer
Heater core hose out 170F per IR thermometer

Another thing I notice is my temperature gauge now sits a little past the middle. I have a 195F thermostat and that is normal position of the temp gauge in warm weather. The car seems to run better with ease of power delivery.

I'm a happy camper!

Last night in 12F ambient, driving on the hwy for an hour I was getting lukewarm heat. Last winter I had great heat.

92 Eco with AC.

I pulled over at a rest stop and noted the following:

1. Coolant temp gauge in the middle

2. Upper rad hose hot, 180F per IR thermometer

3. Lower rad hose cold

4. Upper part of radiator fins hot

5. Bottom of radiator fins cold

6. heater core hose in hot, 180F per IR thermometer

7. heater core hose out hot, 160F per IR thermometer

I think all of the above is normal for 12 F ambient and the thermostat and heater core is OK.

Why am I getting lukewarm heat?

Per the Bently, the amount of heat is controlled by blend door. I assume it blends the ratio of cold fresh air vs hot air from the heater core? Am I getting too much cold air because the blend door is out of adjustment or can it be a vacuum problem to the servos?

I don't want to rip the dash apart to find where the problem is. Is the blend door cable on the heater box accesible without ripping the dash apart? Maybe it's just a matter of adjusting it?

Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 18, 2013, 11:34:33 am
Yeah. Both sides were originally covered, on both doors.

The optimum is to cover both sides, but just one side should be sufficient to route most of the flow the desired direction. As I noted earlier, a 1/4" overhang of cover can help seal around the perimeter of the doors when fully open or closed.

It just occurred to me that the overlapping foam on the doors helps seal the perimeter of the doors (while under air pressure). It does not explain the holes in the doors, however.
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 18, 2013, 11:39:25 am
I did the blend doors in my 89 and the heat still sucks. The core must be plugged.  Pulling the airbox is a PITA. I have heard guys have split the evap section off and removed just the heater section, but that can't be any fun either.

Did you get this fixed? A quick way to tell if your core is plugged is to feel the supply and return hose. If the return is cool to the touch, the core is plugged
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 18, 2013, 11:46:55 am
I've been driving around with the center vent and ducts out. Kneebar and console also out atm and there is so much more room and the heat is fine other than a little too much direct air coming out the vent door. If i add a diffuser plate in front of the vent door that should redirect the flow sideways. What is the purpose of the knee bar? Does it really protect your knee in a frontal collision?
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on February 18, 2013, 05:03:04 pm
I did the blend doors in my 89 and the heat still sucks. The core must be plugged.  Pulling the airbox is a PITA. I have heard guys have split the evap section off and removed just the heater section, but that can't be any fun either.

Did you get this fixed? A quick way to tell if your core is plugged is to feel the supply and return hose. If the return is cool to the touch, the core is plugged

the INTERIOR of the core is the only thing that could be blocked..

the exterior of the core is UNLIKELY to get clogged, because it is pretty well sheltered..

the heater core is BEFORE the foam, and the foam all blows out the vents..

if your core has low flow, reverse flush it with a garden hose on as high as it will go..

then, if that doesnt work.. good luck pulling the dash!
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 18, 2013, 06:06:09 pm
AIUI, the knee rail is to complement the passive belt system.  It may also provide more A-pillar strength in a side impact.


The way I figger it...
 - Loose foam can easily blow into fins of the core.
 - A core with no water flow will have two cool hoses.
 - A core with blocked fins will have two hot hoses, as the air cannot cool the circulating water.

My 89 Jetta has two hot hoses and crappy heat in the cabin. Water can flow easily through the core when i flush it.  That core probably has plugged fins.

I'm currently driving the 85/86 Jetta which has 150oF heat at the vents. I'll pull that 89 core in the spring.


Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 18, 2013, 08:09:03 pm
I think most plugged heater cores are not totally plugged with no flow. What about a partially plugged core with limited flow? Wouldn't that result in a hot supply hose and a cold return hose?

2 hot hoses and low heat = good flow through the core and plugged fins, or cold air bypassing the heater core. Did you try using a leaf blower to clear the blockage?
Title: Re: Luke warm heat 92 Eco
Post by: R.O.R-2.0 on February 19, 2013, 10:23:59 am
I think most plugged heater cores are not totally plugged with no flow. What about a partially plugged core with limited flow? Wouldn't that result in a hot supply hose and a cold return hose?

2 hot hoses and low heat = good flow through the core and plugged fins, or cold air bypassing the heater core. Did you try using a leaf blower to clear the blockage?

the core is BEFORE any foam.. it cant get blocked by foam chunks..

the blend doors have broken windows...
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 19, 2013, 10:51:04 am

the core is BEFORE any foam.. it cant get blocked by foam chunks..
Dude, I have four of these. The temp mixing door can block air from the core - therefore it is before the core when moved into the Cold position.  ::)
Title: Re: Luke warm heat 92 Eco
Post by: 92EcoDiesel Jetta on February 19, 2013, 11:33:53 am

the core is BEFORE any foam.. it cant get blocked by foam chunks..
Dude, I have four of these. The temp mixing door can block air from the core - therefore it is before the core when moved into the Cold position.  ::)

Tyler speaks the truth! There's not that much foam on the blend door though, IMO not enough to completely clog the heater core fins to the point of no heat. Maybe mice built a BIG nest in there? Do you have AC? If no AC, if you take the blower out, can you look at the blower side of the heater core with a mirror or borescope to see what's clogging it?
Title: Re: Luke warm heat 92 Eco
Post by: TylerDurden on February 19, 2013, 12:30:16 pm
I do have the AC evap in there still, but a flexy scope/cam is a good idea.

I got bigger fish to fry on that buggy tho... gonna pin the crank/pulley before anything else.  :-\