Temperature gauge

[Rising damp]

Clearly not a new topic here... But advice sought. After 6 weeks I'm getting through my list of problems on our bus, but the temperature gauge is proving awkward. The red light flashes and goes out, but the gauge doesn't move. The needle remains firmly stuck at the left hand side of the gauge(maximum?) no matter what I do. Should the gauge start on this side? Any ideas?

[1664]

Needle on left hand side of the gauge is 'cold'. Normal position while moving is a tad shy of central position; fan cuts in a tad past central (in my experience). Yes, that is it's 'starting' position.

[kevtherev]

What engine?

remove the sensor wire(s) and touch them together or earth it (engine dependent)

if the gauge moves to the right completely then the sensor is at fault

[Rising damp]

1900 petrol in a 1990 twin slide bus. Engine replaced by previous owner, receipt states"1900 boxer" and very long list of replacement parts....
Back to workshop for further investigations. Markings on gauge confusing, I would have assume him line = cold and fat line = hot?

[1664]

Engine replaced by previous owner, receipt states"1900 boxer"

Engine number should begin DG*******. Number stamped on top of engine block next to that black circular tower to the left of the alternator.

Markings on gauge confusing, I would have assume him line = cold and fat line = hot?

No, fat line is cold (left hand side), thin line is hot (right hand side)

[Rising damp]

The good news is that by removing relay 43 and shorting it out the gauge on the dash works fine. Pleased I don't have to take this to pieces.
I then tried earthing the sender connections but nothing moves... Tried both senders but I believe it's the one on the front of the thermostat housing.
I guess there's a broken wire between the engine bay and glove box? Alternatively is there an obvious problem in that relay 43 is marked 42?
Wiring diagrams in Haynes manual have always been a mystery, but perhaps I'm going to have to get to grips with them.
Thanks for the help so far, I will be so pleased if the solution is to change the relay but I'm not that lucky....

[Rising damp]

Established it's not the relay numbered 42.
Time to delve into the world of coloured wires.

[maddubt25]

any solutions yet same problem as ive got not investigated yet?

[Rising damp]

Mine now works! It was a dead sensor on the thermostat. Not entirely straightforward as the sensors on the thermostat had been swapped round. The one on the front of the thermostat should be the temp gauge(variable resistance) wirh yellow/red and brown wires.the one on the near side does something to the carburettor ( on/off). New sensor £7.98 and some replacement coolant was all it cost.
Have you tried connecting the yellow/red and brown wires together with the ignition on? If the gauge goes all the way to maximum it's the sensor.