Temperature gauge not working

[Welshclimber]

Hoping for some help
The last two days the temperature gauge has started moving (it was pretty steady) and then started to drop. Has now dropped to the far left, which is the same position as when the engine is off.

My original thoughts were that it could be the coolant temperature gauge sensor? I’ve checked the wires and nothing seems loose. Is there a way to check if it’s faulty? Or any other reasons for the temperature gauge behaviour?

Thanks in advance!

[Mocki]

Ok, so 1986 should be late cooling system , so , temp gauge sender is the one at the front of the thermostat housing (facing the front end of the van , furthest away from engine bay ) take off the loom plug from the sender and bridge the connection between the two pins , the gauge should rise to the hot end , and make the red led flash when above 7/8 . If it does , its the sender at fault, if it does not , its a wiring or gage issue and you will need to trace the fault along the loom including the 42/43 module above the fuse box

[Welshclimber]

Thanks so much for your reply. I’ve found it at the front of the thermostat housing. Does that plug just pull off? And then how would I bridge the connection? Sounds like it would need to be while the engine is running to test it? Or just ignition on? This is all very new to me as I’m sure you can tell!

[Mocki]

The plug just pulls off or has a indent spring depending on which plug it is , and just use a metal paper clip of bit of wire poked in the holes in the plug to bridge the connections , and then switch the ignition on, no need to have engine on , and dont do it when engine is hot , its right next to exhaust …….

[Robsey]

Just as a quick add-in...
On the later vans circa 1985 / 1986 and later with the CE1 fusebox (blade fuses), the relay is on the front of the fusebox.
As stated it is numbered either 42 or 43.

Earlier vans with the torpedo style fusebox, the relay is indeed above the fuse box on the a pillar, near to the earth crowns.

[Welshclimber]

Checked the sender today by bridging the connection and the gauge went all the way to the right when I turned the ignition on, so just ordered a new sender. Thanks so much for the help!

[Mocki]

Good news, keep us updated

[Welshclimber]

Ok so have fitted the new sender (with a schoolboy error of getting covered in coolant) and the gauge still isn’t working any thoughts as to why or what else to try? Thanks in advance!

[Mocki]

Ok, so you bridged the plug to diagnose the sender as faulty and it showed the gauge and wiring to work ?

Has the gauge ever worked correctly ??
Have you purchased the correct temperature sender?

If the wiring and plug is working when bridged , it can only be the sender

[Welshclimber]

Thanks for your reply.

So the old sender did work perfectly, until last week when the gauge started dropping, and then stopped working completely. The new sender looked the same as the old one and seemed to fit snuggly when it went back in. when I bridged the connection to test, the gauge went all the way to the right.

Also put a multimeter on the old sender and it’s showing resistance so now I’m very confused!

Tried looking for the earth cable to see if that’s loose but can’t seem to locate it?

[Welshclimber]

Ok so it turns out that I’d assumed the gauge would shoot up to the bottom of the white on turning the ignition, but it doesn’t it just rises slowly. So it was the sender and it’s all fixed now! Thanks so much for your help!