Battery discharging whilst driving

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Battery discharging whilst driving

Post by Tarka »

We have a 1989 Petrol 2.0 van, have replaced battery, starting motor and now alternator but it is still discharging power in the battery whilst running - help any recommendations what do to next. Is it an auto electrician ? It will do about 70 to 80 miles fine but need to trickle charge to get home again

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Re: Battery discharging whilst driving

Post by nicq »

With the engine running check the voltage first out of the large wire on the alternator. It should read above 14 volts. If it does check the voltage across the battery with the engine running it should be similar.
If it reads about 12-5 volts Then with the ignition on but not started check the voltage on the small wire on the alternator, it should be about 12 volts.
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Re: Battery discharging whilst driving

Post by TONYT25T25 »

Does the red ignition light come on when turning key in ignition and then go off when engine is running. Obvious I know but easily missed.  Also do you have a leisure batter and dual charge system fitted, and is it working correctly.
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Re: Battery discharging whilst driving

Post by AngeloEvs »

I had this problem with a Van I had bought.  The problem was traced to the leisure battery charge relay which had been wired incorrectly. The relay failed and the van was running off the leisure battery not the starter battery.  The charge system was perfectly OK but the lights went dim indicating that there was a problem.
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Re: Battery discharging whilst driving

Post by Mocki »

Replace the short lead from the alternator to the starter motor, they go rotten internally and either go high resistance or completely dead . A visual inspection will often not give this away because the insulation look fine .
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