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Author Topic: overheating alternator  (Read 1648 times)

Offline the_GTI_new_guy

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overheating alternator
« on: 29 June 2006, 18:21 »
Stange one here but i have got my car running great now but only when the alternator positive cable is removed from the positve battery termainal! When connected, the engine hesitates, runs poorly and the pully on the alternator gets HOT! Remove the power wire and the pully is cold and the engine becomes alive again. I have read the volatge on the altyernator when running and getting 15 something volts. Shouold i be looking at a new alternator??? Any ideas what my problem could be? Cheer s
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Offline frog

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Re: overheating alternator
« Reply #1 on: 29 June 2006, 18:57 »
With your meter connected to the battery check what voltage you have with the engine idling, rev the engine and the voltage should stay the same, If it does then everything alright with the alternator, if the voltage climbs then possibly the charging diode in the alternator is goosed
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Offline the_GTI_new_guy

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Re: overheating alternator
« Reply #2 on: 29 June 2006, 21:31 »
Its not easy to do as the pully gets SERIOUSLY hot within about 10 seconds and the engine dies at idle, but i will give it a go.
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Offline takethefifth

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Re: overheating alternator
« Reply #3 on: 30 June 2006, 00:08 »
Whats the voltage across the battery when the lead is disconnected? 

Sounds like a goosed alternator... Either that or when you connect up that positive lead for some reason the battery is taking pretty serious current out of the thing. Not sure what would cause that, battery? bad grounding? either way i would still go with alternator.

On another note i was jump starting a bike off my car the other day, now my alternator bearings are already a little dodgy but i was amazed at the difference it made when i connected the bike on! Started really grumbling! I just don't understand why the electricity can have an effect on the mechanics? Is it the magnets?  :laugh:
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Offline Ozz

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Re: overheating alternator
« Reply #4 on: 30 June 2006, 00:59 »
Definately sounds like your alternator needs changing, sounds like iys overcharging, which is the less common way for them to fail.

tt5th, its to do with the electrical load you're putting on the alternator, the more load you put on the more electrical resistance there will be,which results in a stronger force acting against the motion of the alternator. Could probably explain it a lot better than that but its too late to be thinking about electronics!
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Mk2 Gti 8v

Offline rubjonny

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Re: overheating alternator
« Reply #5 on: 30 June 2006, 08:40 »
Over 15v is a little on the high side, I'd expect it to be around 14.5v.  If the pulley gets hot within 10 seconds I'd replace it ASAP, theres defo summat not right there  :shocked:
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Hello my name is John and I'm a dub addict.

Judderi

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Re: overheating alternator
« Reply #6 on: 30 June 2006, 08:44 »
Id make sure your alternator is turning freely. If its seizing then it will put strain on the engine and the belt will cause the pulley to get real hot.

If its like mk2 Ozz said and its overcharging then there will be no need to change the full alternator, simply change the voltage regulator on the side as this is the unit that controlls how much power it puts out.
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