Luke warm heat 92 Eco

[air-cooled or diesel]

the foot duct also has 2 large passages blowing toward rear cabin, i taped these also, usually has crumbling foam sealing these too.

[92EcoDiesel Jetta]

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.

[air-cooled or diesel]

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.

[R.O.R-2.0]

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.

MK2s dont technically have a RECIRC function tho?

[TylerDurden]

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.

[92EcoDiesel Jetta]

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.

[TylerDurden]

I used a small quick-clamp to hold the vent door open while I taped the blend door.




It does help to have small hands. 

[92EcoDiesel Jetta]

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?

[TylerDurden]

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

[air-cooled or diesel]

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.

[TylerDurden]

There is no good reason to run the engine, when the dashpot can be manually retracted to hold the door open for service. 

[92EcoDiesel Jetta]

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.



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?

[TylerDurden]

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.

[scrounger]

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.

[TylerDurden]

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.