Water temperature gauge issues

Hi all,
I have an issue with my temp gauge not working (1983 GTi cabby) and I have searched the forums and found much useful info but my problem still persists so I wonder if anyone can help me please.  So far I have tried remaking the earth connection on the head and checking the earth claw under the dash.  I earthed the wire from the sender both direct to the head and also by running a separate wire to the battery earth - no movement on the gauge.  Gauge fault you would think then so I stripped out the clocks and plugged in a spare set I have, still nothing.  Everything else works on both clocks, I'm just missing the water temp gauge.  Fan cuts in fine and the coolant level light works as it should - I'm at a loss.

To state the obvious but yes my engine was hot whilst doing this - I monitored the oil temp on my MFA just to make sure.

Please can anyone give me some pointers on what else I can check?

Have you tried replacing the sensor?

I haven't but if the gauge was working, according to other threads I've read, when it's directly earthed the gauge should still move which tends to suggest it's something other than the sensor. 
I have a spare sensor so will replace it anyway. Thanks for your reply. 

I guess it's a break in the wire between the sensor and dash, you need to trace the wire back and look/test for a break, as you say if the gauge does not move when earthed then your fault is the gauge.
If you have a spare sensor already try it but I expect it will make no difference.

Do you know if the wire is the same colour at the sensor and the clocks.  I am half tempted just run a fresh wire from the sensor and splice it into the multiplug on the back of the clocks - might be a lot quicker and easier than trying to find a break in the existing wiring.  It will mean stripping the clocks out again but that's not so bad.
Does this wire run through a relay at all do you know?  I have had relay trouble in the past with them sticking as my car was laid up for so long.

1. Does your fuel gauge work?  Yes/No.
No, replace your 10V stabilizer.

Yes, Step 2.
2. Lower your cluster or tilt it so that you can get to the contacts on the back of the water temp gauge.

Using a 9V DC battery connect it to the back of your gauge, if it deflects full scale, leave it on for 2 minutes does the needle stay at full scale? Yes/No.


Yes, Break in the wiring between the Sender and the Cluster or the Cluster pin to the Gauge.

No, Your Gauge is bad, and you need to remove it to be repaired.
see:
repairing your Flaky Water Temp Gauge. - Topless Rabbit Forums

Thanks for your detailed reply.  The only thing is everything else works on the these clocks including fuel gauge.  Even when I fitted my spare clocks I had the same result so I don't think it's clock based but wiring in the car somewhere.

One thing I did notice on my clocks is the little washers under the brass nuts are missing off the studs on the back - same with my spare set too.  Should there be some on an '83?  If so which studs should they be on?  Thanks again

Yes, there probably should be washers as they prevent the Mylar from twisting when tightening the nuts.

Now is you haven't tested your Gauge don't discount it.
They tend to get cold solder joints where the Nica-chrome wire meets the Stud.  I have had to repair all 3 of mine, (yep owned 3 cabby's) to of the replacement gauges out of wreckers needed repair as well, hence my how to, on flaky gauges.

If the Fuel gauge works then you have 10V Stabilized voltage but is that going to the gauge.

If you have 10v at the Gauge, then if you ground the other pin to Earth at the Gauge does your gauge move?
If not, then you have a break in your Mylar from the Pin, and you can test that by placing a jumper on that pin to earth on the connector side, of then the Gauge is working you know that the issue is between the connector and the sender.  If it doesn't then your issue is between the connector and the gauge (mylar).

But you have to know that with a good source, and a good earth the Gauge moves……. If you haven't tested the gauge with a good voltage source and earth then you are wasting your time.

Just because you may have the proper voltage what I would suggest is that you try this test.

Run the Sending units wire to ground.  It should peg that sucker.  If it doesn't then you need to determine where the issue is, wire or gauge.

Wires break as they get brittle with age.
Pin connectors bow out, and the middle pins don't make a secure connection.  

(plumping the connector is a good fix.)
Adding a separate earth to the Brown Wire on the Cluster is also a worthwhile endevour.

But don't ASSUME that the Gauge is functional until you test it or you may be chasing a Monkey around the tree.
You know what Assume is?  ASS-out-of U-and-ME.

From what I have seen on the Gauges (water) is they get flaky and either half work or don't work at all.

I think my water temperature gauge issue is different.  When I switch on the ignition (with or without starting the engine, engine cold) the gauge gently climbs to full scale.  Any ideas

Graham30 said

I think my water temperature gauge issue is different.  When I switch on the ignition (with or without starting the engine, engine cold) the gauge gently climbs to full scale.  Any ideas

If you disconnect the sender wire off the sender unit on the engine, then turn the car on does the gauge full deflect?  if not replace the sender on the engine.

If it still deflects then you have a Shorted wire to Earth from the sender to the Gauge or a bad gauge.
 

New sender gives same result as old one.  Pulling off the wire from the sender makes no difference (full scale).  Checked voltage on this connector whilst off the sender = 3.75V (ignition on).  Briefly earthing this wire sends gauge beyond full scale.
 

Your Gauge going full scale indicates to me that you have an issue with the Wire going to the sender.

Remove enough stuff so you can take the cluster out, but leave it connected.
With the ignition on
Take the Sender wire off, what does the Gauge do?
If it still goes full scale then you have an issue on the cluster.

Why because the higher the resistance the higher the cluster gauge goes.

What is the voltage on the pin of the cluster going to the gauge?  If it is 11-12 Volts that isn't normal with the sender wire disconnected.

I would check all your fuses as if you have a blown fuse something else could be using the Gauge as a ground or voltage source.

Check to see that your temp gauge has 10V on one side.  With the sender unplugged you may see a voltage on the other pin.

Check for corrosion on the Fuse panel if you have had water in the fuse panel issues.

As a test you could run a Jumper wire from the sender and touch it to the pin on the cluster to see if your gauge starts working…  

I would bet you have a grounding issue to the cluster itself as if the wire was broken then the gauge wouldn't see a ground path and remain cold.

The Gauge is a reference between the sender and 10V.
if you have max resistance as in the sender being disconnected  then the gauge shouldn't move.

While I don't think it is a sender or a wire issue to the cluster but it is something that is causing the cluster to misbehave and see a disconnect between the two.

I have seen some really flaky things happen when a 10v stabilizer goes wonky…

I removed the instrument binnacle and pulled off the multi-connector at the back.  I disconnected the wire from the sensor and found that the wire at the sensor end had no resistance to earth.  This does not make sense as I previously found that briefly earthing this cable took the gauge from full scale to beyond full scale.  Nonetheless I cut the wire at the multi-connector end and ran a new wire to the sensor.  I now have a working temperature gauge.  Thanks for all your patient advice.
 

Old post I know - but when you were having these issues - what was the temp guage warning light doing?
My guage appears to work fine (if I earth the sender wire, guage moves) but the light constantly flashes. No level sender or relay on my car….