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Alternator issues. Not getting power from alternator. New one fitting and batt?


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Evening.

I hope someone can shed some light on my problem and point me in the right direction.

My mk3 VR6 is not getting any charge from the alternator. It is circa 12V when the car is running. I have had a new alternator fitted and had a new battery a couple of weeks previous. I have also changed the thick wire from the alternator.

Its a 70amp bosch unit i have fitted. Is there any relays or fuse's that can go?

Any help is greatly appreciated.

Chris

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John, it shouldn't matter which alternator is fitted, they will both produce 14v + when charging.

I agree with russj249, check bulb. Check the output o the alternator from the rear of it, rather than across the battery-see if that makes any diffference.

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Yeah all the wiring is correct and tried the third alternator on tonight. It is not getting power to the batt. But it was generating 22V from the alternator itself when running. Is there something that regulates power. ECU?

The problems all started when i fitted a charger. No belt slip BTW. changed the ecu for a unlocked mapped ecu.

Thanks for the replies so far

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The alternator normally regulates the voltage itself.

The plastic cover hides the 'rectifier pack' which is all the diodes that convert the AC voltage into the DC voltage that the car needs. Also normally built into the rectifier circuit is an overload circuit which should control the voltage and prevent it from going over approx 15v ish.

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Also just a thought, probably won't make.much difference on an alternator, normally its starter motors, but get yourself a jump lead, and attach it to the engine somewhere, preferably where the lifting points are, then the other end onto the negative side of the terminal, this will in effect make a better earth for the engine, so retry the alt output test.

Just make sure you put it to the negative side of the battery or things are gonna get sparky and blown!

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i had this problem with my friends lupo gti was charging at 18.5v. so fitted a new altonator.and no charge. so i got another new altonator after checking all connections. then i traced the wired that plugged into the altonator that works your battery light battery on dash as that didnt come on. but turned out to be broken wire down near the front inner wing.i soldered the wire back together now charging sweet 14.4v. so just follow the blue wire and make sure that is not broken.

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