Hello I'm new to this forum but certainly not new to vws. Having owned many many over the years before getting addicted to Audi quattros.

Ive just bought a low mile 92 model polo fox in need of some love. The first issue I want to address is the fact I have the oil and coolant lights on solid red all the time. I know the oil pressure is good as I've tested with a gauge and the coolant is certainly not overheating. 

Has anyone got any suggestions? 

I'm thinking ground issue or clocks. 

Regards Steven 

Coolant warning light might be the contact at the sensor, damaged cable or the sensor on head.

Low fluid level in the reservoir can also turn on that light. Not all cars have such a float level in the reservoir though.

 

As for oil. If no visible  leaks and oil level above low point on dipstick I'd test the oil pressure sensor.

Resistance when engine cold, and once warmed.

 

The whole of the engine and chassis is ground so the spark-plugs would not spark very well if it was ground issue.

Edited 2 January, 20206 yr by dvderlm

It doesn't have a coolant level sensor. The oil pressure is good both cold and hot. I meant a ground somewhere with the wiring for the clocks rather than a ground in the engine bay. 

Which engine code (size)?

 

With a multimeter what is the resistance of the temp pressure sensor?

Try a spare (known working) oil pressure sensor?

It switches at 0.3 bar I reckon.

 

If there are 2-pin connectors on the sensor perhaps they have worked loose, corroded, or been damaged by previous owner.

 

Sorry, I don't have a Haynes. for 1991 to 1999 Polo, (got either side) so I can't check the wiring diagram to confirm for your model or whether the sensors are NC or NO. But there's usually only one dash clocks earth, so nothing would light up when turn key if the clock earth was bust. However,  the dash backlighting is  dimmable and different circuit - switched with side/headlights.

 

The circuit board on the back of clocks  is flexible plastic, but encased and fairly robust.

The LEDs in dash are solid-state. Cables are insulated and pass through rubber grommet to engine bay so should not short to earth, but the pressure sensor has a moving diaphragm, and the temp sensor gets hot then cold.

The VW blue temp sender in head is known weak point - none OEM/genuine ones are not advised.

I don't know if that temp sensor is used for display in dash and ECU input.

 

 

Thabk you for advice. The blue temp sender if for ecu black for temp gauge. Same as in my digipants mk2 golf. 

Temp gauge works fine. They come on with ignition and remain so after engine starts but they are in a solid state not flashing as you normally get. I'm leaning towards clocks themselves as the wiring all looks good. I will admit haven't managed to spend any time on it since purchase though. My days off start Sunday so will have a couple of days to play about.. Thank you again.

Think I've found the fault. A number of very corroded electrical tracks on the rear of the clocks pcb. New clocks time. 

You might be able to solder on wires parallel to the corroded tracks.

 

So both led conducting through the corrosion to earth?

There's two large sections of corroded tracks. I've sourced another set of clocks anyway.. I'll keep this one for spares but the pcb is shot. 

The saga continues. I fitted the new clicks and the problem persisted. However by chance I noticed if I turned on the lights the dash warnings went off. 

Once I turned the lights off both coolant and oil lights flashed and extinguished as if self testing.. 

I took the headlight apart and it was pretty mucky.. So I cleaned it up and refitted.

Tge same problem continued. I noticed that the lights indicator in the switch comes on with lights. Then extinguishes with ignition.. Weird.

However cleaning up the headlight switch has resulted in the rear fog lights springing back to life..