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Voltage Fluctuating

scam75

scam75

Well-known member
I have noticed the voltage jumping up and down of late on my car. I have checked across the battery in case it was a gauge issue but readings are the same.

When I start her up the voltage sits about 13.2V. When I start to drive or put things on it often drops below 13v. Sometimes it even drops as low as 12.1V with nothing electric switched on. If I stop and switch off then start up again it returns to 13.2V.

The voltage can sometimes dip to around 12V by simply putting the lights on or something but not always. It also soetimes goes back up to 13V whilst driving for no apparent reason?

I have had no electrical issues, car starts 100% every time with strong turnover from battery, just feel this isn't normal behaviour.

First thoughts were maybe voltage regulator or the battery itself or dare I say it the alternator!

Over to the experts..........

PS Can you change a voltage regulator on a 944 alternator or is it a sealed unit?

Thanks

Stuart
 
Id check all the earth points l can find, especially round the dash.
Yes you can change the regulator on the alt. (on my early car anyway)
Mike
 
All sounds normal to me at between 12-13.8 volts. Maximum charging voltage is 13.8v and it may read this after a recent run or battery charge. The no load, engine off, fully charged battery volts should be 12.5. If its left for a while or has a small drain this will drop to 12v. If it goes below 12 v when left standing it will need charging and below 11v is when the problems start.
Hope this helps.
 
I'd echo Mike. Undo, clean and otherwise check every earth point you can find on the car.
In my own case doing this cured a slow- running & tick-over problem that defied every other cure we had tried.
I now have a rock-steady nice high voltage reading that was missing before. Minimal cost as well!
 
So far I have only checked the earth strap from the battery and the big one on the bulkhead, where else should I be checking?
 
Mine is OK unless I do a lot of switch off/switch on driving on a hot day with very small journeys in between, it will then drop to just above 12. Someone on here suggested the rubber gaitor on the alternator acts as a bit of a heat shield, and if perished could course heat to affect the volatge regulator.

Must check mine.....
 
Probably a bit extreme for this but a new alternator makes a huge difference to your voltage reading and stability!!
 
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