SWMBO reported a failure of the heated rear screen over the weekend in her 97 Vectra 1.8. I've checked the switch and the relay and both are OK, . I suspect the multi timer module as she reported that the last time she tried it the ABS light flickered on and the gauges dropped to zero. I don't suspect the screen as the relay doesn't click over when the the switch is pressed, and the switch does not light up either. Does anybody know better before I splash out on a new module?
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If you can wait until tomorrow I'll have a look at the schematics tonight.
In the meantime, have you checked all fuses?
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Thanks Deryck.
All fuses intact.
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Whilst I was thinking ...
Unlikely to be multitimer - would have thought that the gauges and ABS lights do not pass through the multitimer module. Could be a dodgy earth?
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I had a look at the vehicle schematics last night ? it shouldn?t be too bad to fault find.
What test equipment do you have ? a voltmeter would be useful or failing that a 12V lamp on some flying leads, and possibly some ¼? Lucar connectors (male and female).
1.The rear windscreen only operates when the engine is running ? dash switch contact connected directly to the alternator via a blue and white wire with a black and white wire connected from the switch to the multi-timer module.
2.Do other auxiliary circuits such as the radio work ? these are supplied via a main fuse FV2. I think that this is near the battery although I haven?t looked on mine
3.You have said that all fuses are intact but just to be certain check fuses F3 (Rear windscreen) and F22 (Multi-timer and Instruments)
4.Check operation of rear fog, front wiper, rear wiper and interior lighting ? these are controlled by the multi-timer module
5.Remove the relay from the fuse box ? two 40A relays in (roughly) the centre of the fusebox. Position is shown on the back of the fusebox lid.
6.Identify terminal 87 on the relay and transpose the contact to the receptacle in the fusebox. If you have a meter check the resistance between pin 87 and chassis ? not sure of an absolute value but should not be zero
7.Identify terminals 85 and 86 on the relay / fusebox and connect the 12V lamp between these terminals
8.Run the engine and try operating the switch ? the lamp will turn on with the switch operating.
I have more thoughts but let's see where this takes us.
As elekie&a/c doctor said - check the alternator voltage. I would hope that the electronics would survive some overvoltage but this depends on how long the car has been driven with an overvolting alternator.
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Assuming it is a Vectra hatchback or estate rather than a saloon, it may be the wire running through to the hatch has broken where it leaves the car shell & enters the hatch. They eventually give up after years of opening & closing the tailgate.
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Before you do anything ,I would check your alternator charging voltage.It is very common for alternator to overcharge (above 15 volts) and cause all sorts of electrcal gremlins.eg abs ,airbag lights on &failure of hrw circuit,which will not function correctly if alternator is faulty.
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Changed the alternator this morning, very nice in the cold wind! All sorted. Thanks for all the good advice.
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