Help needed: water temp gauge in speedo unit not working

[Bram]

I have problems with my RS2 speedo unit. I can not get the water temp gauge show any temperature. I even went so far by replacing the RS2 water temp gauge with my old S2 water temp gauge, but this also shows no temperature after driving 15 minutes. Before I replaced the S2 speedo with the RS2 one, everything worked just fine, giving me confidence the MFTS is not faulty.

Now it looks like the water temp signal is not being transferred from one of the coloured input connectors behind the speedo (I have no idea what cable the signal is being fed through, brown?), through the clock unit and finally to the water temp gauge connection pins on the speedo PCB.

I found some info at SJM to test the gauge, but I am not sure if I can just put +3V on the signal pin coming from the MFTS. Do I need to test the gauge with the car running?

http://www.sjmautotechnik.com/trouble_shooting/cooling.html#test_gauge

The rest of the RS2 clock unit works fine btw.......

Please advise

[gnutz2]

I'll be watching because my temp gauge does not work either.

What sensor gives the gauge the signal?

[Bram]

Black cable with yellow line from the MFTS?

[Zoig]

If fuel gauge and temperature gauge are not working or are giving out random values, then you might check if the fuel and temperature gauge contact rings are OK on the PCB of the instrument cluster. I had to resolder the contact rings on mine to get temperature and fuel gauge working. I can find a picture of the contact rings in the morning, if it helps.

[Nuvo]

The 26 pin yellow connector pin 2 (T26/2) at the back of the instrument cluster connects to pin 1/T of the electronic thermo switch F76 to the coolant temperature guage via a blue/brown wire.

Temporarily connect this wire to ground and you should see the guage display max temp.

[Bram]

If fuel gauge and temperature gauge are not working or are giving out random values, then you might check if the fuel and temperature gauge contact rings are OK on the PCB of the instrument cluster. I had to resolder the contact rings on mine to get temperature and fuel gauge working. I can find a picture of the contact rings in the morning, if it helps.

Cheers

[Bram]

The 26 pin yellow connector pin 2 (T26/2) at the back of the instrument cluster connects to pin 1/T of the electronic thermo switch F76 to the coolant temperature guage via a blue/brown wire.

Temporarily connect this wire to ground and you should see the guage display max temp.

So testing it with the ignition key switched to on and then connect pint 26 of the instrument cluster to ground? I guess without the engine running is fine, right? Sorry for asking these probably basic questions....

[Zoig]

http://www.pasun.ee/audi/pcb.jpg

The two silver rings on either side are the ones that might cause the trouble. If the copper does not give good enough contact, then resoldering will fix this. Just don't overdo it, the bolts to the gauges must fit trough the holes when done(on the picture it is overdone BTW)

[Nuvo]

So testing it with the ignition key switched to on and then connect pint 26 of the instrument cluster to ground? I guess without the engine running is fine, right? Sorry for asking these probably basic questions....

The ignition switch needs to be on to power the instrument cluster, but the engine doesn't need to be running to test the guage.

[Bram]

Thanks both of you guys. I will give it a try tonight.

[Bram]

Soldering the 2 rings did not solve it. I have had it for today......

As I see the PCB now from the green side it should not be too difficult to measure the routing from the yellow connector to the freshly soldered rings that connect to the gauge.

Yes, I will try this tomorrow night!

[Henkjan]

how about skipping the whole PCB and just soldering the wires to the gauge?

[macspring]

Thanks lads,

I'm watching this thread also as my temperature gauge is dead on my B4 V6 Cabrio, (half works very occasionally) and the petrol gauge on my B4 ACE Avant is intermittent in it's operation, so as I say good thread.

Thanks and kind regards.

[Bram]

how about skipping the whole PCB and just soldering the wires to the gauge?

I have been thinking about that indeed. That would be my last option to do. The PCB copper lines are so short and close to the gauge I should be able to make short wires, but prefer to use the PCB copper lines instead of external wires