Temp Gauge Red Light

[Verne]

I've had the red light in the temperature gauge flash at me on a couple of occasions, but the gauge itself was at normal temperature and it looks like the levels are correct.

First time was when I took Keif for MOT, nothing untoward on the journey there. Mot tester started him up to drive him in to the bay, light was flashing. MOT tester checked coolant etc, gauge was normal. Passed his MOT and when we left for home, light was out.
The latest instance was last night whilst travelling to the local vdub meet. Drove to my mates, no problem and parked up. Left his to go to the meet and light was on again, needle etc was fine. Left the meet to go home, nothing.

What does the light actually tell me and why would it be intermittent

[marlinowner]

It thinks the coolant level is low in the expansion tank. If the level is OK then there is probably a bad contact somewhere between the sender on top of the tank and the gauge.

[Verne]

It thinks the coolant level is low in the expansion tank. If the level is OK then there is probably a bad contact somewhere between the sender on top of the tank and the gauge.

thanks, i'll take another look tomorrow

[Verne]

thanks marlinowner, it was indeed low on coolant

the expansion tank was so dirty, what I thought was the level of coolant was in fact a tide mark

bit of a clean and checking the level through the filler hole it is now at the required level

[timjwharton]

FWIW, the flashing red light of doom is a constant irritation on my van: levels are fine, temp gauge reader sits at noon, but light has a mind of its own...