Club 80-90 Forums

Anyone able to give ideas on this problem?

1988 1.6 TD Syncro with Rev counter (tacho)

Tacho works occasionally. Tapping or bumps in the road encourage it to work or fail.
Temp guage has not worked for a while although the red light flashes and goes off when starting.
Fuel guage failed recently, started again, now seems dead.

Voltage regulator working fine.
Switch cleaner used on the 14 pin contacts.

I took voltage readings with engine running, from the plug of the 14way terminal, with it disconnectedfrom the PCB:
Pin 1, 0v instrument illumination?
Pin 2, 0v highbeam warning?
Pin 3, 0v ground?
Pin 4, void
Pin 5, 14v +ve supply?
Pin 6, 0.01v temp guage and warning light?
Pin 7, 0.01v fuel guage? Tank somewhere between ¾ and 1/4
Pin 8, 13.86v +ve supply?
Pin 9, 7.0v Tacho?
Pin 10, 13.7 blinker warning?
Pin 11, 14.1v alternator light?
Pin 12, 0v oil warning low?
Pin 13, 0.01v oil warning high?
Pin 14, 0.01v ?

Then with 14 pin terminal connected:

Three points on back of tacho 7.0v, 13.7v, 0.05v. It works occasionally. Think there might be an internal fault. Bit worried about dismantling it as that would disturb the PCB, and I don't know what is inside!!!

Temp guage terminal nearest the top, 10.12v.

Fuel guage terminal nearest the top, 10.17v.

To me it looks like the tacho, and both gauges are not working, and that the 14 pin connector is ok. What do you think? I tried tightening the nuts on the guage terminals.. no better.

Bruce

I tested the guages by running wires with IDC from the temperature sensor wire red/yellow and the fuel sender black/violet to earth. Both gave full deflection, so they are OK.
I will try to bypass the PCB to see if that is the problem.

I too am having problems with fuel gauge and temperature gauge sometimes they worked sometimes not and now not working at all . are they connected in some way or is it just coincidence. I presume i need to start with fuses and after that i will definately be out of my depth so would it be more likely electrical or mechanical help i would need.

scammellmanswife wrote:I too am having problems with fuel gauge and temperature gauge sometimes they worked sometimes not and now not working at all . are they connected in some way or is it just coincidence. I presume i need to start with fuses and after that i will definately be out of my depth so would it be more likely electrical or mechanical help i would need.

Yep - they both get their positive voltage via the voltage regulator do-dadd.
If they are both dead but other stuff on the dash works - then I'd suspect that your voltage regulator is dead (or disconnected)

It's this thing on your pcb;

Some useful info in our wiki on those of course = HERE

I've just come back from a run. Full tank and the fuel guage works fine. It then dies at about 1/2 full. Got to be the tank sender. Thats a job for Lee....
I think the temp sensors are out so there's another job for Lee..... The rev counter works 75% of the time. I think I'll settle for that because of the amount of damage I could do getting into the thing.

Temperature sensor and fuel tank sender have now been replaced, and the guages are working fine. Rev counter problem is the same, so if anyone has any ideas I'm listening!!

Hi guys

I am having a VERY similar problem on my 1990 T3 Syncro.

I had a bad joint in the power cable to the starter, resulting in it touching the solenoid and shorting out. I repaired that and now the starter works great, but the rev counter, fuel gauge and temp gauge are all out of order. I replaced the regulator, but no improvement. I have checked every fuse and connection, with no luck. Is there a fuse or relay somewhere? Where do I go from here? Please help....

Regards
Johan
Richards Bay
South Africa

Hi Johan,
The test that set me on the right track for the temp and fuel guages was to put in those Insulation Displacement Connectors with a short lenght of wire on the fuel and temperature sensor wires on the 14 pin connector under the dash panel. If you touch each one to earth, the guages will go to max, if they are ok. There is still the possibility of the PCB being broken. Another way to do this is to short out the tank sender wires by unplugging the connection at the fuel tank and putting a bit of wire or something across the pins, with ignition on. Full deflection on the fuel guage should occur. I have not tried the same with the temp sensor.
The 14 pin connector is a tricky piece of stuff. I used switch cleaner on it and tickled the contacts. They are very delicate though, be careful. Look also at the PCB where the 14 pin connector goes on. They can sometimes be worn out.
Another test that might help, that Peter at wagonbuild.com told me about, is to use a multimeter on pin 6 to earth, the temp sensor, which should read 7.9v cold and 6.2v warm ignition on. By the way the engine will start and run without the 14 connector in place.
The tank sender on pin 7 should give a resistance of 306 ohms empty and 35 ohms full to earth.
Hope this helps...Good luck