Another Passat problem

Honest John Back Room » Technical matters
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Sat 12 Jul 2003 20:56
Another Passat problem - neil 1
I have a 98 Passat, over the last couple of days the clock / computer and mileage readings have vanished after a few minutes. It reappears when ignition is switched off and back on. At the moment it is intermittent but annoying - any ideas out there?
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Sat 12 Jul 2003 21:13
Another Passat problem - sean
Either a dicky connection to the instrument block, a dicky voltage stabiliser or the back up battery has failed.

I can't remember whether the Passat has a little AA sized rechargeable NiCad battery like BMWs do.

At about 5 years old this is what I'd look for.

Instruments out. Unscrew the back case and you should see the battery on the pcb.
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Mon 14 Jul 2003 21:41
Another Passat problem - neil 1
This is only a problem when travelling - when stood clock etc stays on ok. Will i have to take the car to pieces!
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Mon 14 Jul 2003 21:50
Another Passat problem - sean
Aha, not the NiCad then.

This provides instrument power when other supplies are off.

Likely the instrument panel voltage stabiliser. Could also be the car battery. They have a load shedding relay which cuts power to most ancillaries to provide full voltage to the starter circuits. If your car battery is on its way out, the voltage will fall.

On travelling, the alternator raises battery voltage and this could be affecting the instruments.

I'd ask a friendly VW dealer to stick it on the diagnostic box for you. Most will do that gratis. You could bung the fitter a fiver, if he tells you the fault.

No need to touch the instruments now. They'll plug it in via an RS232 terminal.

Good luck mate.
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