Oil cooler-pressure gauge project questions

[doonboggle]

I have a console cluster (CELS) VDO oil pressure gauge (only) that I originally planned to connect to the 1.6L diesel.  From what I see on the 1983 pickup wiring schematic, the circuit line wiring (from instrument cluster connection #16) is blue/black, which matches the existing wires from the gauge … along with the brown and black wires.  

This blu/blk wire apparently continues thru the harness and then ‘out’ to the ‘oil pressure switch’ … which I take to be the switch in the drivers end of head … and then to ground.  In the schematic, this blu/blk circuit line also has a connected diesel leg that connects to the ‘W’ terminal of the alternator which I am presently connected to for recently installed tachometer.

I also see a 'Dynamic Oil Press' icon  It also has a blu/blk wire from it that ends in a 'plug' I know nothing about.

After being advised that I needed to also acquire the pressure sensor, in searching I found a very reasonable combination American version meter with upper oil filter mounted pressure sensor … total of 25.00.  

At the same time I also want to install the factory version oil coolant ‘pancake’ unit.  I have acquired one that came off of a later year pickup that also came with the appropriate oil filter mount … and it had what I ‘think’ is a different type of pressure sensor.

Below are images of both sensors as seemingly indicated by the holes in the bottom shaft.  
Is the small one actually a pressure sensor?









Then once the sensor is installed, which point would be the most appropriate to splice into for gauge readings … the one on the end of the head or the ‘W’ terminal on the alternator?

Or ..... am I all wrong, and need to connect the sensor to the 'Oil Dynamic' item.  If so, I need to know where to find the blue/blk wire to connect to.  
The schematic only shows it going into what appears to be a 6 terminal plug entitled 'Oil Press Control Unit' ... to it's terminal #2.

Lastly I am attaching an image that shows the oil filter mount I will be using with the sensor back in it.  The image also shows what appears to be the same type of ‘switch’ that is installed in the head … where the blu/blk wire is connected.
Am I correct in this presumption … and if so, do I need to wire it into a circuit … or just ignore it in lieu of getting a bolt ‘plug’?
TIA

[Vincent Waldon]

There is likely no factory wiring for the gauge since only the early Cabriolets came from the factory with an oil pressure gauge iirc.  You'll need to run a new wire straight from the pressure sensor to your gauge... far quicker and easier anyways in the long run.  The gauge wiring should have nothing to do with the W terminal or the dynamic oil pressure warning system, which is switch-based.

Speaking of which... the one on the right is a pressure switch not a pressure sensor... but I already told you that in our last email exchange.  You then told me you'd buy it anyways as a spare.  

[doonboggle]

Thanks Vincent.  I gather then that if I run a wire to the sensor ... the big one on the left ... and the other 2 pigtail wire connections to their respective brown (power) and black (ground) places, the gauge will function.

And that the small one on the right is the same as the ones up on the head; and that it ... the small one installed in the filter mount ... is not needed and can be removed.

[Vincent Waldon]

You got 'er.  

The only nuance will be if your engine originally had *two* oil pressure switches... one on the head and one on the original filter flange?

[doonboggle]

It actually has 3 of the same type (in appearance) at the moment;
the head one (blu/blk), and one on each side [blu/wht and blu/yel] of the coolant flange below the head version.  If I left the one in the filter mount, it'd then be a total of 4.

And that's not counting the 'pressure switch' one in the back hole of the mount; both of which I will be removing in lieu of the 'new' pressure sensor.

You got 'er.  

The only nuance will be if your engine originally had *two* oil pressure switches... one on the head and one on the original filter flange?

[R.O.R-2.0]

It actually has 3 of the same type (in appearance) at the moment;
the head one (blu/blk), and one on each side [blu/wht and blu/yel] of the coolant flange below the head version.  If I left the one in the filter mount, it'd then be a total of 4.

And that's not counting the 'pressure switch' one in the back hole of the mount; both of which I will be removing in lieu of the 'new' pressure sensor.

You got 'er.  

The only nuance will be if your engine originally had *two* oil pressure switches... one on the head and one on the original filter flange?

the one on the head is the low pressure switch, the one on the filter flange is the high pressure switch, and the other one on the filter flange is a TEMP sender.. ive never seen a vw with 4 oil pressure switches..

[doonboggle]

As I indicated, the 4th one would be IF I installed the filter mount as it is now configured.

The other 3 are, IMO, common.  I've seen forum postings wherein they are reflected and displayed ... but could not find to reference it today.  Also as I indicated, the first one is at the top of the head by itself in the drivers side end of the head ... and the other 2 being on both sides of the coolant flange at the end of the head ... just beneath the one mentioned above.


[/quote]the one on the head is the low pressure switch, the one on the filter flange is the high pressure switch, and the other one on the filter flange is a TEMP sender.. ive never seen a vw with 4 oil pressure switches..
[/quote]

[Vincent Waldon]

In case we're not all on the same page here, and to help make this clearer should search lead someone here some day... I thought I'd post up a few pictures.

There are three different devices at play here:

1) oil pressure switch: a simple switch that is either on or off, depending on what pressure it is calibrated for
2) oil pressure sensor: a device that converts oil pressure into a varying resistance that can be read by a gauge
3) temperature sensor:  a device that converts temperature into a varying resistance that can be read by a gauge or other device

Here's what they look like:






It is possible that your truck has some fancy wiring... but in general what you should see in the stock wiring is:

- two temperature sensors on the coolant flange.  They measure coolant temperature and report it back to the glow plug relay and temperature gauge on the dash:



- two oil pressure switches... one on the head:



and one on the oil filter flange:



(picture is from a gasser... but it's the same style of flange as in your picture)


So... assuming that this is the setup your truck has, and you're wanting to install an after-market pressure gauge:

- the two coolant temp sensors on the coolant flange are not part of the conversation
- you'll need an additional port into the oil system, if you want to retain the stock oil pressure warning light

There are two main ways to get an additional port into the oil system:

- buy an M10x1 tee, and tee into one of the existing two oil pressure ports (the one on the head or the one on the flange) so that your new sensor shares a port with one of your existing switches
- unscrew the oil temp sensor on your new flange (not needed unless you're also planning to install an oil temp gauge later) and thread the pressure sensor in there




Does that clear things up a bit?

[fatmobile]

Thanks Vincent.  I gather then that if I run a wire to the sensor ... the big one on the left ...

and the other 2 pigtail wire connections to their respective brown (power) and black (ground) places, the gauge will function.

 I'm thinking brown is ground and black is power when ignition is on,.. I'm thinking you are talking about wires on the back of the gauge.

[doonboggle]

Yes Vincent; that shows a bit of clarification on the ongoing.  I've reread my posts, and I see where somewhere in the responses received back, somehow the coolant flange dialogue got off course into coolant temperature switch and sender.  However this does raise another question and will address that later.

So yes, let's get back on track with the gauge system I introduced.
1st ... I have the oil pressure sensor as was shown earlier.
I also have the appropriate oil filter mount as also was shown.  It came with two (2) used units attached ... with the larger one (oil pressure type as evidenced by the hole in the bottom) initiating my query as to whether or not it was useful for my project.  At the time of that post, I knew little about it. 
However, with your help, along with the ETKA pages (see below), I now know it to be a pressure SWITCH ... not SENSOR.


With your information, and the images from ETKA, I conclude that the 'switch' on the filter mount is not needed; and can be removed with the hole being plugged by a sealing bolt.  Incidentally, after cleaning it off, see it is VW part #049919563A which is marked 50c as being for an oil temperature gauge.

Now to the coolant flange units.  According to ETKA there is a unique one for temperature sender, and unique one for switch.  I took one out today to try and decipher which one, but no part number there ... just 08 and 91 ... on different sides of the nut part.  The other one is boxed in by the metal piping, and did not remove it.  Both have the same mushroom head button for wire connecting.

But looking on the web for the ETKA part numbers, one is with the mushroom  ... and the other is with the male terminal type head.  The schematic (not Bentley) shows two (2) blu/yel wires coming thru the harness that in turn connect to these 2 units; and in turn go to 'Coolant temp. switch' and 'Coolant temp. sensor (Ga.)' on the schematic.

I have read forum posts that claim both are the same ... but ETKA shows differently.  At this point I don't know what I have with these 2 units ... so am thinking I should order the proper ones as depicted by ETKA. 
This leads me to this question ... what is the temperature switch one for?  The gauge in my dash cluster shows it's getting input from one of the ones that are mounted.

There are three different devices at play here:
1) oil pressure switch: a simple switch that is either on or off, depending on what pressure it is calibrated for
2) oil pressure sensor: a device that converts oil pressure into a varying resistance that can be read by a gauge
3) temperature sensor:  a device that converts temperature into a varying resistance that can be read by a gauge or other device

It is possible that your truck has some fancy wiring... but in general what you should see in the stock wiring is:
- two temperature sensors on the coolant flange.  They measure coolant temperature and report it back to the glow plug relay and temperature gauge on the dash:
- two oil pressure switches... one on the head:
and one on the oil filter flange:

So... assuming that this is the setup your truck has, and you're wanting to install an after-market pressure gauge:
- the two coolant temp sensors on the coolant flange are not part of the conversation
- you'll need an additional port into the oil system, if you want to retain the stock oil pressure warning light

Does that clear things up a bit?

[Vincent Waldon]

My guess is that there was a version of the Rabbit... a real econo model... with no temp gauge... just a simple "I'm overheating" light... which is why ETKA shows a temp switch as an alternative to the temp sender.

What you have on yours, assuming you have a temperature gauge in your cluster, has got to be a temp sender rather than a switch.... and even though ETKA doesn't show a different picture for the switch (although the part number is in brackets) I bet the temperature switch is bigger than the temp sensor... since it will have internal moving parts, like the oil pressure switch.

In any event... and just my opinion... if what you have is working I'm not sure why you'd want to order new parts.  Find a spare port in the oil pressure system... screw in your new pressure sensor... run a wire to the gauge... and drive!!  

[doonboggle]

Realistic ... at this stage, I don't really know what the two (2) are in the coolant flange.
Like I mentioned, the one I took out today has no identifying marks ... just 08 and 91 on the shoulder ... and it has the (what appears to have been) a white neck. 
However one of them is the feed to the gauge as evidenced by it's output.

But I am still missing something. 
If only a temp. sender is needed for the 1981 temp. gauge ... which yes, I do have ... in the tachometer ... why would VW have 2 blu/yel harness wires which in turn goes to these 2 units ... when apparently only one is needed?

In other words, what I think I am learning, is that once I determine the one that feeds the gauge, I can possibly remove the other one as not needed. 

My expanded purpose in all this is not to only address the install of the oil pressure gauge, but now to understand what I have.  This is the first diesel I have ever had to 'tinker' with ... and am curious as heck. 

The Jetta ... ain't gonna go there; will leave it up to the guru shop I know of in Reno ... versus the 'stealership' shop.

TIA

My guess is that there was a version of the Rabbit... a real econo model... with no temp gauge... just a simple "I'm overheating" light... which is why ETKA shows a temp switch as an alternative to the temp sender.

What you have on yours, assuming you have a temperature gauge in your cluster, has got to be a temp sender rather than a switch.... and even though ETKA doesn't show a different picture for the switch (although the part number is in brackets) I bet the temperature switch is bigger than the temp sensor... since it will have internal moving parts, like the oil pressure switch.

In any event... and just my opinion... if what you have is working I'm not sure why you'd want to order new parts.  Find a spare port in the oil pressure system... screw in your new pressure sensor... run a wire to the gauge... and drive!!  

[Vincent Waldon]

at this stage, I don't really know what the two (2) are in the coolant flange.

There are a couple different styles... some with a mushroom cap and some with a spade lug....but they are typically both coolant temperature sensors: one feeds the temperature gauge on your dash, the other feeds the glow plug relay so that the relay knows how long to run the glow plugs.

[wolfsburged]

Skimmed above... so sorry if this is already covered.

I'm working on a similar situation. I've got the triple gauge setup from a Cabriolet (oil pressure, oil temperature, and volts). With it I got the Cabriolet senders.

The Cabriolets had a larger oil pressure sender similar to what you have, but with two terminals. One is for the pressure switch for the oil pressure warning light, and the other is the gauge sender. This is nice because it simplifies the connection method - no T needed.

I have fitted this dual oil pressure sender/switch on the head, as I want to know if my head has lost oil pressure (should be the first place to see an issue), and I want to retain the warning light.

Cabriolet sender:
http://www.partsgeek.com/gbproducts/WC/7274-01022115.html?utm_source=google&utm_medium=ff&utm_term=1985-1993+Volkswagen+Cabriolet+Oil+Pressure+Sender+FAE+85-93+Volkswagen+Oil+Pressure+Sender+1991+1988&utm_content=YN&utm_campaign=PartsGeek+Google+Base

Now at the filter flange, I have a turbo diesel so I had the oil feed using one port and a pressure switch in the other. If you only have an NA, you should be able to use the other port for the oil temperature sender. In my case I had to use a T to fit the switch and temp. sender.

Not the greatest pic, but you can see the dual sender up top and kinda see the brass T on the flange:

[VW Smokr]

My guess is that there was a version of the Rabbit... a real econo model... with no temp gauge... just a simple "I'm overheating" light... which is why ETKA shows a temp switch as an alternative to the temp sender...

Probably the VW "Bronze Edition", BTDT... a real stripper, not a carpet to be seen, extra plain upholstery, no armrests on doors, and even sold without functional vent windows in the front doors! Radio: Nope! Instruments: Speedo & fuel gauge, that's it! (We replaced the cheap_ _ _  factory cluster with an early Scirocco instrument setup, plus some additional VDO 2 1/16" gauges mounted 'in-dash'... much nicer then!)

J.R.
SoCal