Alternator / Pulley Problem

S

soundboy10

Member
I started getting a weird noise form the engine bay this week, like a bird chirping noise, only after the car had warmed up after about 10 mins and only at low revs. I took it to a local garage and we determined it was around the the alternator, as if it was just stood still running, the noise wasn't present, but if we loaded the car by putting on all the headlights, fog lights, heated rear screen and air con, the noise came back straight away. This seemed quite obvious as the battery was under more pressure so need the alternator to give it more power.

My question was though, how can we completely determine it is a dodgy alternator, or possibly one of the belts or pulleys?? It's hard to pin point the sound, but does sound like its coming from the alternator.

Is there anything else anyone knows about that could help me out.

Cheers

Neil
 
Quick check to see if the alternator is on its way out is to check the voltage across the battery terminals with a volt meter and the engine running. If the alternator is OK the voltage should read between 12 and 13.5 volts. Anything under then the alternator is probably on its way out. If it's over 14v then also a problem as you battery will overcharge. Surprised you garage guy didn't do this when you took it in.

Another quick check is to see if the headlights get brighter if you rev the engines (not excessively!) and dim as you take the revs off.
 
Hi Alan, thanks for your response.

The mechanic didn't think it was a problem with the alternator charging the battery, as there isn't any problem starting up in a morning nor the battery light hasn't come on. It's just something in it that may have gone. That said, we're still not entirely sure it is the alternator. It could be a pulley or a belt, but it's very hard to pinpoint the sound. He would have to have the car in to confirm. I thought if this may have happened to others it might save the messing around and I just get what I need.

I did check whether or not my lights dipped when I got home, but no problem.

Cheers

Neil
 
The difference here as you seem to appreciate is between the alternator bearing being worn and it not functioning to charge. The latter appears to be OK.

It could just as easily be the 2 tensioner pulleys and indeed have replaced them on mine for similar reasons. Loading the altenator by switching on headlights loads the belt so it could as easily be the tensioners, but my money would be on alternator..

I would use the old fashioned way of a rod on the altenator to the ear to listen to the bearings. Care needed but it's a good way.

Next is to loosen the tensioner pulley and see if any of the pulleys or alternator has movement.

After that it's strip down and see what's worn
 
cj10jeeper said:
The difference here as you seem to appreciate is between the alternator bearing being worn and it not functioning to charge. The latter appears to be OK.

It could just as easily be the 2 tensioner pulleys and indeed have replaced them on mine for similar reasons. Loading the altenator by switching on headlights loads the belt so it could as easily be the tensioners, but my money would be on alternator..

I would use the old fashioned way of a rod on the altenator to the ear to listen to the bearings. Care needed but it's a good way.

Next is to loosen the tensioner pulley and see if any of the pulleys or alternator has movement.

After that it's strip down and see what's worn
Click to expand...

'Proper' engineers advice on diagnosis CJ :thumbsup: none of this fault code and change loads of random parts business :)
 
Sadly Eazix that's the current way. 'We changed the alternator and while doing it noticed the pulleys were a little worn so we changed thos too and put a new belt on. All with a warranty and her's the bill for £500 sir....'

and the punter never knew the alternator was perfect and one of the pulleys was needed :thumbsdown:
 
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