Temp gauge reading high but all seems good under hatch

[Paul773car]

1.6d

My gauge recently started reading higher. Its now always to the right of the light in the centre once warmed up, yesterday I got a flashing light and it went almost all the way to the right. Restarted the van and immediately it was lower, I thought that was a bit weird. This morning I checked the spade to the sender cleaned up the contact and replaced the spade with a shiny new one. It is now sitting to the right of the light on idle again And it's -2 outside!!. I have checked the temp of the hoses with a digital thermometer and despite the gauge sitting to the right I'm getting 75 degrees max on any hose. The thermostat isn't even open. As I'm getting about 50 degrees one side and 75 the other.

I have checked the earth's and even shoved a jump lead from the engine to the body in case that was anything to do with it.

So do the senders go bad? And if they do they read hot?

I'll order one tomorrow anyway given they are a fiver but if anyone has any other ideas I'd appreciate the help.

Thanks

Paul

[Mocki]

Yes senders go bad, but it more likely the wiring is the issue , 30 odd year old wiring goes brittle and black internally , changing the resistance the gauge is seeing .

No two senders read the same anyway , and vw say “normal” is anywhere from the 1/3 mark to the 3/4 mark

[Paul773car]

The end of the wire did look corroded but i cut back a fair bit. I thought if the resistance was higher the gauge would read lower? As full ground reads high.

Maybe I'm wrong though?

Paul

[Mocki]

Easy enough to test , measure the sender resistance then measure it at the dash clocks end , disconnected from the console
The gauge should be seeing about 100ohms at normal engine temp

[Paul773car]

Ok cheers will have a look tomorrow and post results I have ordered a new sender too but probably won't be here until between Xmas and new year.

Paul

[AngeloEvs]

Module 43 ( or 42) can sometimes fail and cause a very low resistance across the temp gauge. Easy to check by simply removing it from the fuse box on later vans. Early vans it is close to the fuse box.

[Paul773car]

So I checked the resistance at the sender to ground and at the dash wire to ground. Pretty much the same reading. So I'll fit the new sender when it arrives and if it's still reading high get a 42 relay ordered.

Thanks

Paul

[AngeloEvs]

I would remove module 42 or 43 to see if it is the problem before ordering a replacement.

[Paul773car]

So today the new sender came. Popped it in seemed to read even higher than the old one.

I pulled relay 43 (I didn't have the newer 42) no change. Flushed the cooling system and changed the thermostat seems better. With the heater on the needle sits just to the left of the red light with it off it sits slightly to the right. The old thermostat was still working though seemed to open a touch later and slower than the new one.

For now I'll just keep an eye on it.

Thanks all for the advice