Fluctuating instruments

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robertverhey
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Fluctuating instruments

Post by robertverhey »

As part of my annual service, I'm going to try to track down the reason for my fluctuating instrument needles. Not referring to the fuel gauge, that's a given. But all the others (oil, temp especially, voltmeter) have saint vitus dance, and take a little leap up or down when, for instance, you operate the window switch, or the air con kicks in or out. In short, they can't be relied on to provide an accurate reading. And it drives me nuts.

Has anyone successfully got to the bottom of this? I assume mine's not the only one that does it.

Robert
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amarshall
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Re: Fluctuating instruments

Post by amarshall »

Faulty voltage regulator for the instrument panel ?
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robertverhey
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Re: Fluctuating instruments

Post by robertverhey »

Does it actually have one? I scoured the circuit diagrams some time ago and couldn't find one, so I assumed that they're all running on 12V......but more than happy to be set straight on this!
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Re: Fluctuating instruments

Post by amarshall »

Hmmm - good point.

Pre-85 there's a "voltage stabiliser" shown as number 35 on the parts list for horns relays and control units, but no apparent equivalent on post-86 (although number 34 is missing from the list). Given that the system is really being drive by rectified AC from a source which should be > 12V I would have expected some sort of regulation there....curious...

OK - what about a fault resistor on the voltmeter instead (post-85) ? If the drop there is incorrect it could cause some interesting readings when the circuit is loaded.
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Re: Fluctuating instruments

Post by htiek »

A lot of my peculiar instrument fluctuations were cured when I found that the main earth to the pedal box was not connected. (This is from my dodgy memory banks as it was quite a while ago!)
Mind you, bad earths are always a good thing to check for....

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Re: Fluctuating instruments

Post by Ozzy_UK »

i am getting weird issues like this too suddenly, very damp weather maybe?
Oz
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