Engine Sensors - ID and Operation help please.....

Hi,

This is a pic of my 1800 Carb Engine in a '93 Cabrio.



I'm just looking for a bit of advice as to which sensor is which and how they operate…..

I believe 1 & 2 are the OIL pressure sensors 0.3 and 1.8 Bar. Is that correct? If so which is which? I guess one is normally open and the other is normally closed at zero pressure?

Am I right in thinking that , if either trips, then the red Oil LED comes on? Should that LED be constant or flashing?

I also have a red LED within the temperature gauge. This flashes with ignition on then goes out after a few seconds. Can anybody tell me which sensor that is coupled to? I have read about "Low Coolant Level " sensor  but I don't believe I have one. There is certainly nothing in the coolant header tank. Anywhere else I can look?

Is the red led in the Temp gauge perhaps simply "over temperature" indication?

I'm also tracking down the fact that I have a permanent 12v feed at the yellow/red cable on the temp sender at "3". I suspect some mix up in the plugs on the CE1 Fuse Unit. BUT if anyone has any ideas that might point me in the right direction - I'm all ears!!

I'm aware that's a lot of questions but I can't believe I'm the first to come this way!

Cheers



Peter

 

Hi Peter, you're right about 1 & 2 being oil pressure sensors. Number 2 is the low pressure switch and makes the oil light flash on the dash if pressure drops below 0.3 bar at idle. Number 1 is the 1.8 bar sensor and makes the light flash as well as sounds a warning buzzer if the pressure drops below 1.8 bar at 2000rpm or above.

3 are definitely the coolant sensors but I can't remember which one does what exactly. The low coolant level sensor would be in the expansion tank so if yours doesn't have one there then it won't be anywhere else. And I'm not entirely sure but I believe the permanent wire going to that coolant sensor is for the overrun cooling, but again, not entirely sure.

Hope that helps and someone else should be able to confirm the other things

1. Oil temperature switch Black base that sends Oil temps to Center console.

on a 93 there would of been a white sender that is white which is shown that is a Low oil pressure high RPM that would flash the light and activate the buzzer in rear of the speedo.

3. The water outlet flange should have 2 senders one BLUE which ha a blue connector. it is the Coolant Temp Sender for the Digifant ECU.  It also contains the black Coolant Sender with the black connector for the Dash Water temp gauge .

2. Low oil pressure at idle which will flicker the light. and the oil pressure Gauge in the center console which is missing and you have a oil pressure low at low RPM.
The Correct sender is 035-919-561.

As I see that you have a Hall sender on your diz, the typical sender is the Hall sensor, that with the Digifant ecu advances or retards the timing along with the knock sensor. It usually doesn't have a Vacuum assisted advance.

I see that your water outlet flange has a sender on the rear with wires cut, so there has been some modifications that I am unaware of.

I will flat tell you that the Plastic water outlet flange is a time bomb that is waiting to happen.

You can replace it with a metal flange off a later CIS 16v engine along with the 16V sender.  

from this plastic part that I replaced about every 6months (mine is a daily driver that gets average 50 miles a day on one and about 30 on the other cab.)  



to this: 16 V cis based no oil cooler flange.



I replaced the black sender with another black single pin.

I replaced the blue CTS sender with one from a 16V.



here is a thread on eliminating most plastic flanges on the 90ish cabbies.
https://www.vwvortex.com/threads/i-still-hate-plastic-parts-but-thanks-tolusina.6907318/?id=6907318&highlight=hate+plastic+parts

Now to be honest I have never seen a VW 90 anything with a Factory Carb as I have owned a 90, 92, and 93.  As in the stated all 90's were digifant 1 or digifant 2.  All had that plastic flange from the Debil his self.  I was replacing about 2 per car year.  Who ever thought to replace a metal flange with the plastic one and attach to the radiator should of been drummed out of the VW engineering works, I blame the Accountants for this cost reduced part.   

Thanks for the responses so far. I feel I'm understanding the functions a little better….

This my block outlet. I certainly intend to change it to a metal one ASAP but thought I owuld establish that all else is well before doing so!



As you see it has 3 sensors in it - quite different from Briano's.

The part nos are : - 2 x 191 919 369B These are the straightforward on/off. One for the Auto choke and one for the manifold heater relay?

The other is 251 919 501 which is the temperature gauge sender i.e. a sensor where the resistance varies with temp..

This is where I have my constant 12v - which I am sure is incorrect!

So………. the temp gauge in the dash is fed with a stabilised 10v with the other terminal connecting to earth via a) the CE1 and b) the block sender. As the resistance varies with temp so the gauge indicates.

Working on advice I connected a cable across the sender plug terminals. This should have made the gauge indicate high temp - in the event all I got was melted wires!

I removed the dashboard and clocks assy with the expectation of the temp gauge having quietly corroded away. (I now seem to have been fiddling with the dashboard and clocks for what feels like months!)

In the event the gauge operated fine when fed with 9v and I found a spare sender which I tested with hot water to find that the res does vary. I set up a bench test and found that all worked as expected

The wiring bears little resemblance to any of the diagrams and plug allocations. So I have bypassed the plugs at the rear of the CE1 and made a connection direct from the gauge/clocks 14 way plug to the sensor. Have done a trial refit today and all seems well so far. The W T Gauge definitely moves. If earthed I get full deflection and a flashing warning light!

Happy days!

Will look at fitting the NOS sensor tomorrow (requires a bit of coolant to be drained)