Red flashing light on temperature guage

[steviedee]

I've tried to find answers to this problem on the site but I'm still scratching my head.

The temp gauge light is always flashing. It flashes for a few seconds when first start up then stops for a few seconds and then starts up again and continues.

The coolant level is topped up and the vehicle doesnt overheat (1.9 petrol DG) even on long journeys.
I have removed the sensor from expansion tank and put a meter between the 2 contacts when out of the coolant - no current registered. Then popped the sensor into the coolant and I got a reading, which suggests to me that the sensor is working.
I checked the connector in the engine compartment and that seems ok also. As a definite check, I snipped the 2 wires going through the connector and joined the wires together,effectively bypassing the connector just in case there was a fault there but the light still flashes.
So I am fairly confident the fault isnt in the engine bay, unless the solenoid block the brown wire passes through could be at fault?
Any suggetsions??

[fodtommo]

I've tried to find answers to this problem on the site but I'm still scratching my head.

The temp gauge light is always flashing. It flashes for a few seconds when first start up then stops for a few seconds and then starts up again and continues.

The coolant level is topped up and the vehicle doesnt overheat (1.9 petrol DG) even on long journeys.
I have removed the sensor from expansion tank and put a meter between the 2 contacts when out of the coolant - no current registered. Then popped the sensor into the coolant and I got a reading, which suggests to me that the sensor is working.
As a definite check, I snipped the 2 wires going through the connector and joined the wires together,effectively bypassing the connector just in case there was a fault there but the light still flashes.

The checks you have done indeed show that the sensor is working, but it also shows that its working incorrectly.

When current flows (presumably to earth) the light comes on - so this should happen when the water level is low in the expansion tank - instead it is working when the water level is full but going off when it thinks it is empty.

Ive never had a good look at it so not 100% sure of its mechanism - a float of some sort imagine?

Take it out - work out how it works and work out why its working backwards see if you can fix it - if not replace it.

[Mocki]

if you unplug the sensor in the header tank, the light should flash.
the sensor acts like its not there if there is no water on its probes.
so the reading you got are correct.

you have a broken wire between the plug for the sensor and the dash.
connecting the two wires together should have stopped the light flashing, but you have to reset the system between tests, by switching the key off and on again. iirc

chances are its a bad connection at the dash end . try giving the plug on the dash pod a jiggle.

[Ian Hulley]

Jerjiggle it gerGranville !

[steviedee]

right here goes:
I located the control switch (black cube with a number 43 on it tucked up above the fuse box inside the dash panel, very well hidden!) and removed it. Started the engine and after the 30 second test run, it stopped flashing! So I 'thought' i had cracked it and located the problem ...... until it started flashing again. It flashes with the control switch in or removed. I borrowed a control switch from another T25 which doesnt have the flashing problem and fitted it - no difference.
I have disconnected the long connector at the back of the dash and it looks clean. I fitted and removed it a few times in case there was a bad connection but it hasnt solved the problem.

I'm wondering now if its something to do with the temperature side as the light flashes to warn against low coolant or high temperature and the above test was done with a running engine . We went on a long journey at the weekend in swealtering heat and the temp guage sat solid in the middle throughout. This was in Derbyshire with plenty of 3rd gear revving to get up hills as well. So its not overheating

[steviedee]

I'm giving up. Anyone know how to remove the sodding bulb?

[jaymo]

I'm having exactly the same problem and although removing the bulb would kind of sort the problem, the problem will still be there. Arghhhhh!!

[AngeloEvs]

If your temp LED is flashing continually with module 43 removed and the temp guage is sitting in the middle you probably have a wiring/connection fault as the LED will nornally only trigger if the engine temp is higher than normal with module 43 removed. Removing the LED is not a solution and very difficult to do anyway.

It could be an intermittent fault in the Earth path, poor connections at the sender in the thermostat housing, loose nuts that secure the temperature gauge to the membrane PCB on the rear of the dash or poor connection issue at the edge connector that feeds the dash.

[steviedee]

I sort of fixed it. Found 3 nuts at the back of the dash pod which corresponds to temp guage. Fiddled with these and the light has stopped. Although the temp guage is working ok, I have no flashing light at all even on startup (or sometimes just a faint glimmer. ) .
Does anyone know if the light actuates by a broken circuit (sort of fail - safe) or by power input? I think it is getting a rogue power feed from somewhere

[hammy44]

the top or middle one opperates the red light the other two are the temp gauge you may not have a good connection at the top unscrew it and tighten or giggle it again to see if it comes on.

[AngeloEvs]

The middle nut that secures the temp guage provides the earth connection for the micro chip inside the temp guage. The micro chip controls the LED, if the connection of the middle nut is loose or not in good contact with the membrane PCB then the LED will stop working, come on intermittently, etc, but since it is designed to flash for ten seconds it can give the impression it is continually on.

It is just another earth gremlin in a long list that can cause the temp LED to flash. Might be worth removing the nut and checking the condition of the copper membrane track under the middle nut for breakage, tarnishing, etc. You could try a link wire and directly connect the middle nut to a known good earth and see if the LED behaves correctly.

[JJJackson]

Hi I posted the same problem, today I had some welding done on the rear suspension for the MOT on my newly aquired bus so the battery was disconnected. When the battery was reconnected no more flashing light apart from at start up!

[hammy44]

Hi I posted the same problem, today I had some welding done on the rear suspension for the MOT on my newly aquired bus so the battery was disconnected. When the battery was reconnected no more flashing light apart from at start up!

unfortunately didnt work for me but worth a try

[heatonwhite]

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strange one this, drove back from minehead like this yesterday, 12hrs later got back to bolton. we had the AA out (frankley services)who assured me its not overheating, any ideas?
regards dave

[pilgrim55]

Not a fix but might give you peace of mind.

Water light flashed intermitently on my now deceased van. Have had to put instrument cluster from it in my imported van to get it MOT'd and UK street legal, it's still flashing where as the KPH one the cluster is a temp replacement one for didn't, just down to old age, worn connections and dodgy circuits I think.

Be happy that you've had it checked and it's OK, if it's an issue for you fit another gauge in a pod.