Fixed: Alternators question

q292u

q292u

Member
United-Kingdom
Do the diesels and petrols use the same alternator?

Asking because I can get a second hand one for £30 but not sure which it is?
 
q292u said:
Do the diesels and petrols use the same alternator?

Asking because I can get a second hand one for £30 but not sure which it is?
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There are a bunch of different power alternators, depending on the engine, as well as if the car has air con fitted. You should be able to find the right one, as well as part numbers, here.
 
It is pretty unusual for the alternator to die, what is most common is the voltage regulator module packs up. They are in the range of £20 - £35 new.
 
No. To my memory the 1.4 petrols have 90A, the 1.6FSI have 110A.
The diesels have 120 or 140A, all with freewheel pulleys. And at least a 1.2TDI without AC have 90A, but the not same as the petrols.
 
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Do the petrol A2s use a free-wheeling alternator pulley like the TDIs do?
I don’t believe they do, but I might be wrong.

Cheers,

Tom
 
timmus said:
Do the petrol A2s use a free-wheeling alternator pulley like the TDIs do?
I don’t believe they do, but I might be wrong.

Cheers,

Tom
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I agree and see that my post is badly formulated. I will adjust, thanks.
 
Joga said:
I agree and see that my post is badly formulated. I will adjust, thanks.
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Ah, sorry, my reply wasn’t directed specifically at your reply, but was just a general question.
Reading your post, it seems my understanding is correct: the petrol A2s use a fixed pulley rather than a free-wheeling version. Definitely another factor to consider when purchasing a replacement alternator. 🙂👍🏻
 
In terms of cross-compatibility, the 90A petrol alternator in the 1.4i can be replaced by the 110A alternator from the FSi. To the best of my knowledge both use non-clutched pulleys.

The 120A alternator in the earlier Tdi can be replaced by the 140A alternator from a later one. These do use clutched pulleys (INA being one of the noteworthy suppliers that I know about owing to the pulley on my project car grenading itself off into the undertray after gently squeaking after startup for a month or so beforehand!)
 
Ok, so the issue I have, the reason I was looking at replacement alternator, is that I get a charging warning light on startup. This goes away if I rev it (and stays off,). I've also had the pas fail as I reverse out of the drive, which I assume is also power related.
Am I better off investigating changing the regulator? Is that an easy job?
 
q292u said:
Ok, so the issue I have, the reason I was looking at replacement alternator, is that I get a charging warning light on startup. This goes away if I rev it (and stays off,). I've also had the pas fail as I reverse out of the drive, which I assume is also power related.
Am I better off investigating changing the regulator? Is that an easy job?
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It sounds like the alternator is working if revving the car makes the light go out, I’ve not heard of partial failures before, I would assume that it would work until it doesn’t…
(I’m sure someone here will correct me if I’m wrong)

Might be worth some more investigating, trying the car with a different battery if you have one, or monitoring the battery voltage before during and after startup, and during different engine speeds maybe
 
Indi said:
It sounds like the alternator is working if revving the car makes the light go out, I’ve not heard of partial failures before, I would assume that it would work until it doesn’t…
(I’m sure someone here will correct me if I’m wrong)

Might be worth some more investigating, trying the car with a different battery if you have one, or monitoring the battery voltage before during and after startup, and during different engine speeds maybe
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Battery is literally brand new. Had same problem with previous battery. So probably not that..
 
It’s really odd that some have had alternators fail and the only symptoms have been slow start, power steering drop out etc. When mine went, it created huge problems with traction/ abs/ steering angle lights and buzzer. I replaced everything and it turned out to be the alternator!
 
I have seen alternators fail to produce enough charge - rectifier issue normally. Also seen them "work" but when switched off rapidly drain the car battery, also possibly the rectifier / regulator.
 
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