Coolant gauge u/s

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ricicles
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Coolant gauge u/s

Post by ricicles »

Our coolant gauge went crazy some time ago. As soon as the engine is running the needle climbs to its Highest position and the flashing light comes on. I have tried to earth it earth it directly from the back of the gauge but it still does the same.. Any ideas?

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Re: Coolant gauge u/s

Post by marlinowner »

Firstly, is the coolant level OK? ie header tank full (the tank inside the engine compartment with the sensor in the top)?
If that is OK, try removing the "relay" number 42 or 43 near the fuses, it sends the coolant low signal to the gauge. If light still flashes then either the gauge is faulty, the coolant temp sender is faulty, the gauge isn't earthed, or there is a short to ground somewhere in the wiring between the gauge and the relay or temp sender. If the light stops flashing then most likely cause is a bad contact in the wiring to the coolant level sensor, or could be a faulty sensor or relay.
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ricicles
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Re: Coolant gauge u/s

Post by ricicles »

Awesome. I will have a look a play with the relay. Levels are all correct. Just popped a new pair of heads on as the old ones had problems. The water is now staying were it should. Deffo electrical problem. Great fun for a colour blind old fart.

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Re: Coolant gauge u/s

Post by MidLifeCrisis »

Yep - What Marlinowner said ^^^^^
But for a quick test - try disconnecting the connector to the temperature sensor at the engine - if that stops the needle moving then I'd guess that your temperature sensor has gone bad?
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ricicles
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Re: Coolant gauge u/s

Post by ricicles »

MidLifeCrisis wrote:Yep - What Marlinowner said ^^^^^
But for a quick test - try disconnecting the connector to the temperature sensor at the engine - if that stops the needle moving then I'd guess that your temperature sensor has gone bad?
Done that and it behaves the same connected or not. I have been thinking that indicates a fault in the wiring between the switch and the guages. I have continuity up to the box in the engine bay and have checked the dash itself for continuity and that appears OK. But I don't really have a clue what I am doing!

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Re: Coolant gauge u/s

Post by MidLifeCrisis »

ricicles wrote:
MidLifeCrisis wrote:Yep - What Marlinowner said ^^^^^
But for a quick test - try disconnecting the connector to the temperature sensor at the engine - if that stops the needle moving then I'd guess that your temperature sensor has gone bad?
Done that and it behaves the same connected or not. I have been thinking that indicates a fault in the wiring between the switch and the guages. I have continuity up to the box in the engine bay and have checked the dash itself for continuity and that appears OK. But I don't really have a clue what I am doing!
Do as Marlinowner says then and yank the 42 relay out - see if that makes any difference?
The gauge is going to 'full hot' because something is grounding that temp sensor signal wire somewhere - so pulling the 42 relay will determine if it's that relay that is u/s or if it's a cabling issue??
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Re: Coolant gauge u/s

Post by ghost123uk »

Remember that (as we have been talking about on another thread) when the low coolant sensor (on the left hand white tank) is activated, along with the thing on the relay panel (which looks like a relay, but isn't) on some models the needle is pushed over to the right (so one can see the warning LED). I am thinking it is pretty certain you have either a faulty control module (No 42 or more likely 43) or a fault in the wiring from that module to the two pronged sensor in the left hand white tank. Also worth cleaning up those prongs with a bit of fine wet & dry,
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ricicles
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Re: Coolant gauge u/s

Post by ricicles »

OK. Tried removing the relay the guages behaved the same way. Removed and cleaned the level switch in the header tank (it was pretty clean) no change. Have gone back to the switches in the thermostat housing. Fiddled around to try and remove the wire from the forward facing switch (burned my hand twice on the exhaust manifold) :shock: didn't get it off but the flashing light stopped and the needle dropped. Thought I would check to see if the level switch was working by removing the plug from the top and bingo the warning light started to flash. Looks like it could be the front facing temp switch that is faulty?

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Re: Coolant gauge u/s

Post by ghost123uk »

Certainly does :ok

When changing it, watch out for the rubber "O" ring.

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Slight aside = you may have already noticed that once you trigger the low level (prong) sensor, even if you plug it back in, it keeps flashing until you turn the ignition off and on again to re-set it (it's a fail safe feature).

Slight aside 2 = when you pulled that plug to trigger the low level sensor, when the LEd started to flash, did the needle stay where it was or move up the scale? Also, when you looked at the box of tricks on the relay panel (that looks like a relay) did you note if it was numbered 42 or 43 ?
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Re: Coolant gauge u/s

Post by ricicles »

It's a 43. Yes I had to stop and restart for the light to stop flashing. I didn't take notice what the needle was doing! Doh

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Re: Coolant gauge u/s

Post by ricicles »

Huge thanks guys. It's working :mrgreen:

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