Alternator Overcharging?

[TonyMills]

Hi,

I have a standard alternator on a Volvo MD7A. This charges two semi deep cycle 12 volt batteries which are linked. The system has been in place for about two years.

In the last couple of months when I start the engine the charge rate goes up to 15 volts. After a short while 5-10 mnutes it drops back to 13 volts. Where I run the motor for a couple of hours it will periodically race up to 15 volts and then settle back again to 13.

I cant see an explantation for this. Nor am I clear whether it is doing any damage?

I'd appreciate any clues as to causes. Should I be concerned? (I am of course!)

Regards
TonyM

 

[Talbot]

have you tried using a different voltmeter to see if the voltmeter is the problem?

 

[VicS]

Yes you should be concerned. it might not be causing any problems at the moment but if it gets worse it will. After checking all connections suspect the regulator. (I've had one do more or less what you describe except that I had an ammeter that periodically went full scale rather than a voltmeter

13 volts is too low, just as 15 is too high.

An auto electrician should be able to check it out for you

 

[halcyon]

Sounds a bit like a faulty transitor in the regulator. Works ok till it gets hot, breaksdown and stops working ( 13 volt ), cools down and starts conducting ( 15 volt ), works till it gets hot again.

If you get it checked, tell them it is intermittent, fails when it gets hot, else it sounds like it will work cold, and if they just run it up it will check out ok.

Brian

 

[TonyMills]

Thanks for that advice Vic, I will get it checked out.

I'm getting the reading off both the battery voltmeter and the engine voltmeter so I'm sure its not a false reading.

Regards
TonyM