120 A to 90 A Alternator

S4_dan

S4_dan

Fire up the Quattro!
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My Audi has a 120A alternator fitted. I fitted a 2nd hand one at 120A and it failed.

I've charged the battery up and done a drain check and it's showing 0.19 amp drain with the car locked.

I'm going to a scrap yard on monday and if there are no 120A alternators, would a 90 Amp suffice? I wouldn't use the Air con (I can only think this is the reason why it has a 120 amp unit fitted?!)

Cheers,

Dan
 
Larger size alternator is to support the larger size battery and power requirements of the car.
A 90 A alternator would probably be used on a 1.6, 1.8 petrol basic model. The 120A is needed to support glow, plugs, larger starting loads , more electrical equipment that the car has.
0.19A , 190ma with the car locked is a lot more than I would expect, usually around 0.05A or 50mA .
Do you have an amp in the car thats not being turned off or a bulb on such as the glove box, boot etc.

Karl
 
It's a 1.8 (ADR) Automatic with Air con.

The battery had never drained prior to the alternator failing. I fitted a 2nd hand one and it got red hot within minutes and died. Then the battery drained as I left that alternator all connected up for 3 days.

When I had the drivers door open and car unlocked the amperage was at 0.89A

The Batt+ lead from the alternator isn't shorting to earth. I didn't test the small 12V lead though,

The car was running fine up until just after christmas when the alternator died on my friend as he pulled up at work. He got the AA out and the guy jumped started the car and said alternator has failed, probably the regulator. I bought the car off him last week.

This is where I currently am in trying to sort it.

As the car only has front leccy windows and climatronic I wondered if the 90A would suffice.
 
I was looking at the signature with 2.5 V6 quattro. If it's a 1.8 petrol then a 90A will probably do.

Karl.
 
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yeh my 1.8T only has a 90A, and the one we had before had a 70A. Be reet.

0.19A seems like a lot of draw though. With the drivers door open you'll have all the interior illumination on hence the higher value there, but i'd expect <100ma with the car off/locked etc.

typical battery is 70AH, and a 0.19A draw would probably drain it enough that it would struggle to start the car in a week, and be completely dead in 2 weeks.
 
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aragorn said:
yeh my 1.8T only has a 90A, and the one we had before had a 70A. Be reet.

0.19A seems like a lot of draw though. With the drivers door open you'll have all the interior illumination on hence the higher value there, but i'd expect <100ma with the car off/locked etc.

typical battery is 70AH, and a 0.19A draw would probably drain it enough that it would struggle to start the car in a week, and be completely dead in 2 weeks.
Click to expand...

Great stuff, that makes life a little easier. I wonder if it has been replaced before then?

I am fully charging the battery again and will do some test on the drain. A case of pulling a fuse by fuse scenario......

Do the B5's suffer with any water ingress in the ECU boxes? Just wondering if the drain could be in there with the relays etc?

Dan
 
Just for info, the replacement alternator is a Valeo unit rated at 90 amps and is working fine.
The original unit was a Bosch 120 Amp.
 
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