Author Topic: Is it my alternator? (Read 4872 times)

blackcat · « **on:** October 24, 2007, 06:23:37 am »

ok, so I'm new here and need some help with my 1.9 TD golf.

My alternator belt has been squealing when started from cold for a few months but I haven't got round to changing it yet.....

However, last night when driving I noticed that whenever I went over about 2500 revs, the battery light flickers on and the rev counter drops to zero. It then righted itself and the light stopped flashing.....

This morning, however, the rev counter is not working at all and the battery light is constantly on. But the car is running fine, it revs and accelerates fine :?:

Is my alternator on the way out?

Also the oil light flashes whenever the battery light flashes (it has enough oil!)

Any advice would be appreciated

Op-Ivy · « **Reply #1 on:** October 24, 2007, 07:27:28 am »

If you know your belt is loose I would start there. Tighten it up and see what happens.

burn_your_money · « **Reply #2 on:** October 24, 2007, 07:31:46 am »

My car did the exact same thing (less the oil light) when my belt was slipping. Last time it was because of a punctured coolant line spraying coolant on the alternator though :roll:

blackcat · « **Reply #3 on:** October 24, 2007, 07:32:42 am »

Can't tighten it, it's an automatic tensioner.

blackcat · « **Reply #4 on:** October 24, 2007, 07:33:59 am »

Quote from: "burn_your_money"

My car did the exact same thing (less the oil light) when my belt was slipping. Last time it was because of a punctured coolant line spraying coolant on the alternator though :roll:

ah ok, I will change the belt first before I do anything else then, ta.

Vincent Waldon · « **Reply #5 on:** October 24, 2007, 08:37:26 am »

Quote from: "blackcat"

ok, so I'm new here and need some help with my 1.9 TD golf.

My alternator belt has been squealing when started from cold for a few months but I haven't got round to changing it yet.....

However, last night when driving I noticed that whenever I went over about 2500 revs, the battery light flickers on and the rev counter drops to zero. It then righted itself and the light stopped flashing.....

This morning, however, the rev counter is not working at all and the battery light is constantly on. But the car is running fine, it revs and accelerates fine :?:

Is my alternator on the way out?

Also the oil light flashes whenever the battery light flashes (it has enough oil!)

Any advice would be appreciated

A couple of things:

The oil pressure sensor system is sensitive to engine RPM (it looks at different sensors depending on RPM)... and it learns about engine RPM from the W-signal on the alternator (same signal that drives the tach) so there's a really good chance your oil light flickering in time with the dropping tach is simply another symptom of your alternator issue.

In terms of the alternator: intermittent alternator function could indeed be a slipping belt... either a belt that's old and glazed *or* a tensioner spring that's lost its tension. An inspection of the belt and tensioner should help.

If you now have no tach and a red alternator light then your alternator has quit... the engine will run with no issues but one of these fine mornings your car will not start. Besides the belt and tensioner the next thing to check is the brushes... the fact that you had some intermittent symptoms suggests that they have been on the edge of their wear limit and are now done. They can be removed and checked with the alternator in the car.. just makes sure you pull the negative cable from the battery to avoid any unpleasant sparks !

Good luck... let us know what you find out !

Vince

blackcat · « **Reply #6 on:** October 24, 2007, 09:03:48 am »

Wow, thanks for the comprehensive info there!

I shall inspect belt/tensioner/alternator later and see if I can work out what is wrong!

Jetta Fan · « **Reply #7 on:** October 24, 2007, 09:04:34 am »

Something else to check.....the tensioner pulley. My light and tach were acting up last fall. Kind of an intermittent thing, but then one day the pulley flew apart on my (the bearings where it goes on the tensioner arm) while I was driving. Seems the pulley was getting bad and not keeping the proper tension on the belt, causing the light to come on and the tach to quit. The tensioner itself was fine. Replaced the pulley (and the belt because it shreded it) and I was good to go.

Just watch the routing of the belt. I didn't have a diagram to follow so I called a local guy that works on VWs and he told me how to do it. :roll: Ended up pinching itself together and not allowing anything to turn and when I tried to start it (I resorted to push starting it down a hill) I broke my timing belt. Needless to say, I didn't give him the TB job.

blackcat · « **Reply #8 on:** October 29, 2007, 02:16:40 am »

Well, it's fixed now (I hope), thanks for all your suggestions!

We took alternator off and took it apart then put it back on with a new belt and it is working fine now!

Not sure how long it'll keep working for as brushes looked like they were in need of replacing soon. At least I know now what to do if it happens again!

Thanks again for helping out a newbie

jtanguay · « **Reply #9 on:** October 29, 2007, 08:50:51 am »

the belt was probably stretched so far the automatic tensioner had no more tension left.