Temperature gauge only works while coasting ?

[simleybarter]

Hello there.
Another funny qurk of my van.
The temperature gauge in only working while coasting with the clutch in.
Any ideas ?

[MidLifeCrisis]

Go on - elaborate a little ..........

So if you coast with clutch not depressed it works?
If you rev with clutch in it works?
What happens when 'it doesn't work' - does the needle go to the cold end or the hot end?
Does this only happen in motion or can you recreate while stationary?

[simleybarter]

Yep if i coast with it out of gear, or with clutch pressed in it will creep up, but if i rev engine the needle goes back down.
yep if the van is just idling in the drive for a while the needle goes up as well
by the way its the 1.7 d.

[MidLifeCrisis]

Errr - that sort of sounds like normal/correct operation;
When your coasting (low revs) the coolant pump can't pump coolant quite as much so the flow is reduced and the coolant gets hotter; Rev the engine a bit, pump works faster, coolant moves round move and is cooled by flowing through the radiator so it gets cool again .....
Also idling in the drive there is no airflow over the radiator so cooling efficiency is reduced and coolant tends to heat up (hence why the radiator fan usually kicks in to increase airflow over the radiator)

But this all supposes that the needle movement is only small (maybe the equivalent of the width of the led light in the gauge) - if it's more than that then your cooling system may not be working at top efficiency .....

[simleybarter]

Thanks for trying but Im pretty sure that its not right as my needle would always be in the middle position after driving for 20min or so, and maybe creep up a bit higher if driving long distance on a hot day.
But now the needle just sits on the bottom even after long drive and the engine warmed up.
The needle only registers correct temp when not reving.

[marlinowner]

Could thermostat stuck open coupled with inefficient water pump give those symptoms?

[simleybarter]

I changed the thermostat, made no difference.
The problem has now grown to the oil warning light coming on intermittently also.
Have changed the oil temp sensor and the oil level is correct.
Can these problems be connected ?

[mickeyflyn]

I had similar probs with my gage and dash lights , turned out to be bad connection on the pcb in the clocks.

[kevtherev]

Hello there.
Another funny qurk of my van.
The temperature gauge in only working while coasting with the clutch in.
Any ideas ?

Yes, change the temp sensor, or clean up the contacts at least.