Club 80-90 Forums

I sudden have the coolant flashing light syndrome. I’ve been working through the guides to identify the root cause and am a bit stumped.

All levels are fine.
I’ve tried methodically disconnecting the level sensor, temp sender and relay 43 in turn and still get the flashing. Shorting out the temp sender sends the temp right up so figure that’s working.
Disconnecting everything, including the relay it still flashes. I’d assumed disconnecting the relay would stop it flashing....where else is it getting signal from?

I’m going to replace the dalek cap, level sender and coolant sensor as a matter of course. What else could it be, a the actual gauge?

Any other ideas?

Thanks all

A long shot

I have been led to believe the relay pulses the ground line to bring the light on, perhaps a bad earth connection to sender or bad sender causing a signal ripple would cause the light but not full gauge.

Also possible a bad regulator or earth at dash might do this if there is ripple.

try disconnecting the sender line at the dash, easier said than done, I cut the wire on mine to investigate a fault, it's just a wire easy to join it again.

If you don't want to do that take the temp gauge out and bench test it with a 10v source or spare regulator

careful changing level sensor often new ones don't fit and leak, if the plug removed does not stop it then it's probably not the sensor, only buy genuine pressure cap or alternative one from Brickwerks

also rumour early vans had a slightly different behavior to the low level senor and guage, what year is it? - best add the year to your signature

Remove the module 43, this will disconnect the coolant level sender part of the circuit and prevent it triggering the coolant led. Switch the ignition on and wait a few seconds, if the coolant led continues to flash after a few seconds then the fault is not with the level sender or module 43 but elsewhere.

If after doing the above, the temperature gauge is reading normal then the following are known causes:-

a). Poor earth at the earth crown next to the fuse box.
b). Centre nut of the temp gauge loose or poor contact with PCB membrane.
c). Poor earth at the dashboard multiconnector.
d). Internal Temp Gauge Capacitor
e). Intermittent regulator voltage due to poor connections in the regulator socket.
f). Regulator voltage at or below 9.5 v. ( should be 10v approx.)
g). Intermittent short circuit at temperature sender connection/wiring loom.

Thanks folks for your detailed responses.
I have it sorted now (well my father who is much cleverer than I am has been looking at it and sorted it).
Turned out to be dirty connections from the gauge to the PCB. All cleaned up and working great now.
Thanks again