Alternator light showing after timing belt change.

[peter hh]

Had my timing belt and water pump changed last week. But yesterday (8 days after change) I popped cash machine and I noticed my alternator light had came on.

Now could this be coincidence or could the garage have not done something correctly. I've had a quick google and I've found that if the belt wasn't timed right it could cause the problem or if a connector wasn't connected to the battery then the problem could arise.

Any thoughts?

[Laurel Green]

I'd give the connector a wiggle to make sure it is seated properly.

[Puddenchucker]

What car is it?

Chances are the alternator drive belt has been removed when replacing the timing belt and may not have been correctly tensioned or the tensioner has come loose.

[MagneticMeerkat]

The alternator is generally driven off the auxiliary belt; which is separate to the timing belt. The auxiliary has to come off to allow removal of the timing covers, and then it needs to be properly tensioned when it is refitted. Did they replace it at the same time? You don't have to but may as well as belts are cheap and it doesn't take any longer, I digress.

If it's an older car usual method is to tension the auxiliary belt using the alternator body, in effect the alternator is free to pivot, and is loosened and pushed in to take the tension off, conversely it's pulled out and tightened to put the tension back. Alternatively a separate tensioner wheel may be fitted.

I'd guess, starting with the obvious, that the auxiliary belt is a bit loose. When this happens it tends to slip over the alternator pulley, rather than properly spinning it. As such the alternator loses efficiency. Is the belt making any noise? Check this by opening the bonnet, starting the engine and listening. It helps to rev the engine whilst doing this. If the belt is at all loose it will make a shrieking noise. Another thing to do is press the belt with your fingers, with the engine off lol (!), at the point of greatest gap between two of the pulleys. It should deflect inwards by a millimetre or so, anything more and it's loose.

[peter hh]

Thanks for the replies guys.

I've just been and inspected the alternator and battery now it's daylight. I've gone to check the tension of the alternator belt to find it's not there and is snapped hanging from the bottom of the bumper.

So it's at the garage now having a replacement belt.

[Ozzie Osmond]

Definitely agree loose alternator belt is most likely.

[barker22]

peter hh said:

Thanks for the replies guys.

I've just been and inspected the alternator and battery now it's daylight. I've gone to check the tension of the alternator belt to find it's not there and is snapped hanging from the bottom of the bumper.

So it's at the garage now having a replacement belt.

Let me guess, they re used the old belt?
Really bad practice that.

[lbc]

Alternator bearing may have seized, causing belt to wear rapidly.

Had this on an Audi a few years ago which was a common fault.

[peter hh]

barker22 said:

peter hh said:

Thanks for the replies guys.

I've just been and inspected the alternator and battery now it's daylight. I've gone to check the tension of the alternator belt to find it's not there and is snapped hanging from the bottom of the bumper.

So it's at the garage now having a replacement belt.

Let me guess, they re used the old belt?
Really bad practice that.

No the old belt had snapped in half, they fitted me a new one for £20.