Voltage regulator ? Maybe.....

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Victor Meldrew
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Voltage regulator ? Maybe.....

Post by Victor Meldrew » Thu Sep 17, 2020 12:30 pm

Has anyone else experienced an indicated 999 degC water temp?

The engine at idle would normally sit around 80 degC, it has now developed a WTF is going on here symptom.

Engine at idle indicating around 88-94 degC. Temperature indication jumping around erratically.

Turn the heater fan on and the indicated temp jumps 10 deg, Turn the lights on and another 10 deg. Switch on full beam and you are indicating 999 degC.

Turn them all off again and temp drops back to almost normal.

Turn the engine off and put the ignition back on again and the temp indicates the correct 80 degC



So this looks like a voltage related issue.
Is it the Stack regulator, alternator regulator or a sign that the battery is on its last legs?
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campbell
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Re: Voltage regulator ? Maybe.....

Post by campbell » Fri Sep 18, 2020 7:51 am

Rings a bell.

Dodgy earth?
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Ferg
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Re: Voltage regulator ? Maybe.....

Post by Ferg » Fri Sep 18, 2020 8:04 pm

Definitely start by checking the earths


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robin
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Re: Voltage regulator ? Maybe.....

Post by robin » Sun Sep 20, 2020 9:26 pm

On S1 the temperature sensor is a one-wire sensor with the other "wire" being the earth path through the chassis. This is why when you turn on the heater fan or headlights, the temperature steps up/down - it's because you're adding a (small) offset voltage across the earth and that gets summed into what the stack sees.

Do you happen to have those funny lights - Xenon or whatever they are - the ones that need a driver module? If so I would be looking there first (if they can be replaced with the original lights and modules removed, that's what I would be doing).

Do the full beam lights actually light up properly?

Could also be a fault around the full-beam tell tale on the dash rather than the actual full beam lights.

To get 999 is quite extreme, you have to create a significant voltage across the earth and I cannot see that happening because of the current return of the full beam lights.

What happens if you stall it in 1st, handbrake on, don't touch ignition key, sitting with the full beams on and indicated 999? Does the temp drop back to normal? I ask because once stalled the alternator stops sourcing the current for the headlights and so the earth return path now goes to the battery rather than the alternator. So if there is no change, it kind of cannot be the normal earthing points - it must be the earthing of the stack itself. Mice or water ingress behind the dash?
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Victor Meldrew
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Re: Voltage regulator ? Maybe.....

Post by Victor Meldrew » Mon Sep 21, 2020 2:35 pm

robin wrote:
Sun Sep 20, 2020 9:26 pm

Do you happen to have those funny lights - Xenon or whatever they are - the ones that need a driver module? If so I would be looking there first (if they can be replaced with the original lights and modules removed, that's what I would be doing).

I have LED lights which are a plug and play sealed unit. No module to speak of.

I am seeing a change when I turn on the heater fan and when I use the wipers.
When I turn on "Everything" I am seeing the 999 figure.
As soon as the cooling fan is called for the figure jumps. and it normally stays high after that, I suspect because of the load drawn by the cooling fan.

Ok, check the earths first.
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robin
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Re: Voltage regulator ? Maybe.....

Post by robin » Tue Sep 22, 2020 9:46 pm

Do the stalling test.
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Victor Meldrew
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Re: Voltage regulator ? Maybe.....

Post by Victor Meldrew » Tue Sep 22, 2020 9:50 pm

robin wrote:
Tue Sep 22, 2020 9:46 pm
Do the stalling test.
I will as soon as I get home again. Vicky tucked up in the garage while I’m away.

Thanks Robin
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