Thanks for taking the time to reply
An auto electrician checked these areas 12 months ago for £90 but couldn't find the reason. He was all for replacing the instrument cluster.
I've been on other forums and the opinion is it could be a voltage stabiliser problem causing the speedo fluctuation. I have seen this fault where the speedo responds almost as a "Rev counter" when you blip the throttle.
The thinking is that the voltage feed to the instuments is not being stabilised as it should be.
I am now trying to establish whether a Corsa C has an internal voltage stabiliser within the instrument cluster (On previous models it was fitted externally).
If I can conclusively establish this I will most likely fit new instruments.
Thanks once again
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You have made no mention of the speed sensor in the gear box or provided any voltages. I suspect there is a stabiliser in the instrument pod but it will also feed the temp and fuel gauge and you make no mention of them mis-behaving. Regards Peter
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You have made no mention of the speed sensor in the gear box ....
The speed sensor on Vauxhalls is usually in one of the hubs.
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Hi
Yeah one of the first things we checked was the speed sensor on the hub. Nothing wrong there though!
As far as the instruments go, its mainly the speedo that shows issue, though I have seen the rev counter misbehave in the past. The temp and fuel guages have never had any issue.
This would therefore rule out a voltage stabiliser issue?
I spoke to someone today who suggested it could be a dry joint in the instruments??? Any opinions on this possibility.
Before I had the alternator swapped we checked the amperages and it was putting 7 amps into the system. We also checked the voltages (No figures at the moment), but the car was ok on start up, but once any consumers were switched on the readings went into total discharge. When the wife's driving the car, she finds that if she switches everything off the speedo will just waver around the approximate speed.
Thanks for replying
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Thanks Dave.
OP how was the sensor tested did they check the ouput waveform from the Hub speed sensor. Regards Peter
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Personally I think you need to sort out the battery discharge problem starting at the alternator and working through the circuits - I suspect (just gut feel, no evidence) that the speedo fluctuation etc. is being caused by the drop in battery voltage.
Have you monitored the battery voltage, and maybe the accessory voltage - at the cigar lighter point for example - when this weird stuff is going on?
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Thinking a bit more,what are the voltages at the battery? You should get 12.6V with the ignition off, around 14V with fast idle but no load,dropping to about 13.5V with headlights etc. on. Hopefully someone can correct my figures if they're a bit out.
The fact that it gets worse the colder it gets points the finger more at the battery than the alternator I reckon, but some voltage measurements would be good.
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I would suggest get an auto-elect tech to check the voltage drops on both the power and earth wires to and from the alternator/battery and chassis earth points.Any problems here can cause a malfunction of the electronics to engine Ecu and dash.hth
On the right track there I think-I had the exact same problem with an E34 BMW 520 for months-traced to a loose earth bolt where the battery negative lead is connected to the body underneath the front of the rear seat.
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