Temp guage problem

[Santa79]

Well, I was going to change my thermostat and housing since (after an hour drive) the engine would not heat up at all.
It would appear that they have both been changed fairly recently. So I went through all of the receipts that came with the van and they had been done 8 months ago.

So, how do I check the sender? Am I right in thinking I need to put 12v across it to see if the needle moves to full heat? Or is there a simple way?

Ta in advance

[Santa79]

I should probably mention that the heaters don't blow any warm air, let alone hot air either.
And the coolant level is fine too.

[MidLifeCrisis]

Your sensor will either have one or two wires going to it;
If it has two wires then just connect them together and the gauge should move to show "hot"
If there is only one wire going to the sensor then connect that to a good ground (short piece of wire to the engine block works well) and the gauge should move to show "hot"

What are the symptoms of the problem - is it just the gauge reading cold or do you think that the thermostat is not working? A bad thermostat would not cause the gauge to stay at cold.
After a drive is your radiator hot to the touch?

[Ralf85]

Well, I was going to change my thermostat and housing since (after an hour drive) the engine would not heat up at all.

The engine would always be hot after driving for that amount of time.

As said above is the radiator warm after driving? If so then the problem is possibly to be an airlock in the heater matrix.
The temperature gauges can be temperamental. Mine worked on and off for years. Touch wood it has now working normally again for the past two years.

[Santa79]

After shorting the sender to earth, the needle moves to hot. So I know that it is either the sender or the thermostat (I will take it out tomorrow to see if the rad warms up).
If the radiator is cold, I shall bleed it and see how that goes for me.

The thing is, I can't understand why the heater will not blow any hot air. It is my (limited) understanding that the thermostat/sender that would cause this?

[123-jn]

Definately the sender as even with the stat stuck shut heat gets into the water around the sender from the bypass hose and heater hoses and directly from the head. AS for the heater not getting hot sounds like an airlock or a knackered heater valve. Have you also bled the radiator via the bleed screw on the top left as you look at it. After a short run the water should be hot coming out of there too , and the Rad hot all the way up.

[Santa79]

Definately the sender as even with the stat stuck shut heat gets into the water around the sender from the bypass hose and heater hoses and directly from the head. AS for the heater not getting hot sounds like an airlock or a knackered heater valve. Have you also bled the radiator via the bleed screw on the top left as you look at it. After a short run the water should be hot coming out of there too , and the Rad hot all the way up.

I shall bleed bleed the system at the rad and the engine bleed valve first.
Then I'll take it on a quick run and check the rad is getting hot all the way up. I it does, I shall look into the heater valve.

I may well get a new sender and replace it first anyway too.
I shall post results tomorrow afternoon!!

[Santa79]

Time for a bit of an update...
Over the last few weeks, I have ran the van and the radiator is hot all the way up.
I replaced the sender too (mostly as it is easier to do and diagnose the fault than straight to changing the thermostat).

The problem still exists. So.... I shall fit a new thermostat (but I will test it in water first, to make sure it is ok before I fit it)