Temp gauge

Hello. I have a few issues with my new car. 

But one in particular is the temp gauge. 

If I click the ignition on the temp light flashes constantly and temp gauge goes to max without even starting the car. 
Then when started it settle down to between 3/4 and 1/2  and light stops. 

It's does this whether the temp sensor on the thermostat housing is plugged in or unplugged. 

Turn the car off, then back on again and it starts again, flashing light temp gauge to the top. 

What's the likely cause please? 

1.3 81. 

Other symptoms are, car gets warm pretty quickly. Both rad pipes hot, matrix pipes hot, fan kicks in, but the expansion tank water doesn't get particularly warm so suspecting water pump as when I rev it no water is returning to the expansion tank so not sure the system is flowing properly. 




Water pump?
Air lock? 

Take your sender wires off.
Isolate them with a piece of tape.

Turn your car on, if the water gauge still flashes then you may have a bad gauge, as a nicked sender wire would or could cause the gauge to go to 3/4 to full hot and flash the light.  The Light should flash for a couple of times on key in as a test, but stop.  

Then if you want to try this as well.
Take a 9V DC battery and connect the negative side to the engine frame, and the Positive side to the Sender wire.  Your gauge go should 3/4 to full hot but I have never seen the lamp flash with this test.  (key isn't in).

If this test works then your wire isn't nicked and your issue is usually the gauge.

If your fuel gauge is acting wonky, then I would suspect that your 10V stabilizer is the issue, as you didn't mention that I thought I would add that here as well as your Fuel Gauge and your Water temp gauge uses a stabilized 10v to power them.  That stabilized voltage ensures that you don't see gauge dips with the alternator and loads to it being applied.  If it goes bad it can either kill both gauges or cause 12V to be applied to both gauges and makes the read full all the time.

Thanks Brian I'll try the battery test. 

As said this with the key clicked to on gauge is full and flashing whether the wire is connected or not.. or by isolating do you mean disconnect the sender wire totally from the gauge end too?

no, just disconnect it from the engine.  Insert the key if the gauges go full hot, and flashes then it is probably the gauge. or the 10V Stabilizer.

I would test the stabilizer, it is the transistor looking thing on the back of the cluster.  One pin is +battery to ground 11.5 to 12v + DC, the middle is ground, and the third leg is usually 9.5v to 10V+DC.  if you get other readings then it is probably bad.  If you get the same on both end legs to the middle it is bad.

The Bentley has the write up on it in the back.  The Cabriolet's 10V write up is

Some of the earlier Golfs had a gauge test circuit..
IT was a way to verify that all your dash lights ang gauges came on to say they were still working.  

Have you cleaned and or replaced your engine to frame and frame to battery ground?  You could do my quick test to validate that your main grounds are good.

Electrics when wonky likes to find it's own path to ground, and I have seen speedometer/clutch cables as well as other things as the main ground point which usually fries things a tad.  

I have seen pic's of melted clusters when starting the car as well as ECU's on the Digifants Smoke Testing as the ECU is being used for start ground.  The age of the wires on these are getting to critical mass as engine oil's cause the insulation to become brittle and break wires when bent, or chafing.  

https://www.volkswagenownersclub.com/threads/brianos-quick-grounds-test.134637/

Well this afternoon the gauge sometimes stated maxed out and constantly flashed.. or maxed out and flashed for about 10 secs whilst the car started and then stopped flashing and dropped down… this happened with the wire either connected or not… 

So yes I'll pull the cluster out and check those voltages. Thanks matey. 👍🏼

Just checked those voltages on the stabiliser and if got a steady 10v. 


Is there an extra earth I can add in whilst the clocks are hanging out? 

I'm suspecting maybe a dodgy earth?

In fact, taking the cluster out completely has uncovered a very poor condition ribbon connector, it's in a really bad way… I can kill the rev counter and temp gauge just by touching the connector… the pcb traces are all peeling and nasty looking. 

Might be a perfect opportunity to convert to a mph cluster. 

Different clocks plugged in, extra earth added, padded out the ribbon cable. 

New temp sensor..

Same issue… still flashed and goes to max… I did see the temp gauge die and that killed the fuel gauge… then it all came back. 

Good news is I've got. Mph speedo, and it doesn't die when I wiggle the wiring. 

WTH is going on? 

Just to add once it's started and running it stops flashing after about 5 or so seconds but only settles to half on the temp gauge. 

I'm gonna do the stat and pump etc at the weekend… but I've a feeling the gauge is a totally separate issue… that I really thought I'd fix with the different clocks. 

Also just noticed the battery light doesn't come on when you click the key on. 

The alternator is charging the battery though. 

Now it won't start… was running, went lumpy and died. Just turns over. 

Think possibly killed the coil but not sure. 

I give up…. Just a very expensive paperweight currently. 

Roach said

Different clocks plugged in, extra earth added, padded out the ribbon cable. 

New temp sensor..

Same issue… still flashed and goes to max… I did see the temp gauge die and that killed the fuel gauge… then it all came back. 

Good news is I've got. Mph speedo, and it doesn't die when I wiggle the wiring. 

WTH is going on? 

Just to add once it's started and running it stops flashing after about 5 or so seconds but only settles to half on the temp gauge. 

I'm gonna do the stat and pump etc at the weekend… but I've a feeling the gauge is a totally separate issue… that I really thought I'd fix with the different clocks. 

Put the Original cluster back in.  
Then fix your wiring issues.  

For the fuel gauge to die, as well as the temp, that is a good sign that the 10V stabilizer is acting the hiney.  

You have some wiring issues.  I can see a DVOM in your future.  

Usually the Alternator won't produce a charge if the light isn't on at key in.  You have something back feeding either ground or power to your cluster.

Thanks for your help as ever. 

But I'm over it. 

I'll do the mechanicals and pass it to my man who can…. Then sell it.