Weird Alternator Problem - help please

Hi everyone - Happy New Year.

I thought I would round off 2010 by treating my 1988 3.5 EFI Vogue SE Auto to a wash after its last pay and play day a couple of weeks ago. It had been working fine since then.

I gave it a hosing under the bonnet, not deliberately directing the jet on the alternator, but it did get wet.

I then turned the car round and noticed the ignition warning light flash briefly, but thought nothing of it until I parked the car back on the drive and a harsh grinding noise started. On investigation this was coming from the alternator. It sounded like something was stuck inside and had been caught between the rotating and static parts. Also the rev counter does not work until the engine is reved a bit and the ignition warning light is glowing until revs are increased. Sometimes the noise will come and go instantly i.e. not start gradually or fade away. Other times when I start the car there is no noise for a few seconds and then it starts when revs are increased.

I replaced the regulator, brushes, slip rings and rectifier in November and all had been working perfectly until today.

So I stripped the alternator down and found no signs of any parts rubbing against each other, or other damage. No mud inside anywhere near the working parts, and the brushes and slip rings are fine. While I had it apart I put new bearings in, just in case one of them had been damaged somehow. So I have had a good look at every component from all angles, and when reassembled the shaft spins as smooth as silk.

All to no avail - when I put it back on the car the noise was just as bad.

I also tried running the car without the alternator drive belt in case the noise was coming from an adjacent component like the power steering pump, but the noise stopped.

I had done nothing to the car today apart from hosing under the bonnet - could this have damaged the rectifier? If so I could understand the sympoms, apart from the noise.

Have any of you guys and gals got any ideas, cos I am flummoxed?

Pete

you've not dislodged a pipe or cable or something so its touching the alt fan have you?

blue beasty said:

you've not dislodged a pipe or cable or something so its touching the alt fan have you?

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No, and I have had the alternator off and back on again three times today so I would have noticed anything like that. And that might explain the noise (but not it coming and going), but not the other symptoms.

Thanks for thinking about it though!

Pete

Only a guess, but it could be shorted turns on the field windings, motors and transformers can make a terrible noise if that happens.

Datatek said:

Only a guess, but it could be shorted turns on the field windings, motors and transformers can make a terrible noise if that happens.

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Thanks Datatek.

Come to think of it there was a little bit of mud on the field windings, but I imagine that has been there for two weeks. I had kept the engine running while I was hosing, to try to avoid problems.

Does that mean it's FUBARed then? Is there any test I can do? I have a multimeter.

Pete

Pete The Biker said:

Thanks Datatek.

Come to think of it there was a little bit of mud on the field windings, but I imagine that has been there for two weeks. I had kept the engine running while I was hosing, to try to avoid problems.

Does that mean it's FUBARed then? Is there any test I can do? I have a multimeter.

Pete

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If you take it apart, you could check for shorts from the windings to the frame, but you would need more then a normal multimeter to check for shorted turns.

Datatek said:

If you take it apart, you could check for shorts from the windings to the frame, but you would need more then a normal multimeter to check for shorted turns.

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You would need a MEGGER for that, and them are DEATH to DIODES if you muff it. Megger sends out 1,000 volts DC to test insulation.

It's not just a squealing belt is it? OK OK!!!!! Just asking!

I take it you have examined the belt tensioner very carefully ......

CharlesY

CharlesY said:

You would need a MEGGER for that, and them are DEATH to DIODES if you muff it. Megger sends out 1,000 volts DC to test insulation.

It's not just a squealing belt is it? OK OK!!!!! Just asking!

CharlesY

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Hi Charles nice to see you back on something less heated than Jay's saga. You can test for shorted turns with less damaging kit than a Megger, I use a micro ohm tester for in situe testing, it will measure very small differences in field coil resistance that can be due to shorted turns. A megger is good for insulation testing.

A Happy and Prosperous New Year to you

CharlesY said:

I take it you have examined the belt tensioner very carefully ......

CharlesY

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Thhanks fro your reply. Yes I have checked - and readjusted it several times. It is a harsh mechanical grinding noise, not a squeal (unfortunately!).

Pete

Pete, it sounds as though the alternator has been thoroughly checked, so perhaps it is OK after all.
You said 'I also tried running the car without the alternator drive belt in case the noise was coming from an adjacent component like the power steering pump, but the noise stopped' So doesn't this mean it is in fact one of those other components making the grinding noise, or perhaps crap on the belt somewhere ? Just a thought

A bit rudimentary and you say you have cleaned it but a squirt of switch cleaner and a gentle blast from an air line could dislodge something you've missed. A contaminated belt can sound rough as well. Does it make a noise with the belt off and you turn it by hand?

Datatek said:

Only a guess, but it could be shorted turns on the field windings, motors and transformers can make a terrible noise if that happens.

Click to expand...

Well, more investigation today, and Datatek gets the prize for the best reply! - Thank you very much!

I started the car again today and unlike Friday, this time there was no life from the alternator at all (last time it would work if I rev'd up), and no noise!

So on the basis that I had replaced everything else in the alternator recently, that only left the coils to check. A few minutes with the multimeter confirmed that there was indeed a short from the wires in the field (static) coil to the frame.

So, the problem was identified but where was the fault? I gave the coil a good clean with a toothbrush and warm water to get the mud off (not a lot really, it was dirty rather than caked with mud) so that I could see what was what.

The only place I could see a possible fault was on one of the wires where it looped round into one of the slots in the frame - it looked like there was a little bit of spark damage. It wasn't easy to see because it wasn't the top wire, and all the wires were hidden under one of those cardboard(?) inserts which hold the wires in some of the slots.

On the basis that I had nothing to lose, I thought I would have a go at a repair, although to be perfectly honest I didn't hold out much hope.

So, the first step was to very gently prise out the cardboard so that I could get at the wires, and then one by one lift them out of the slot so that I could examine them. The first picture shows the wires lifted out, the lack of lacquer insulation on the second one up, and the damaged insulation on the edge of the slot. It looks like the insulation had broken down just on the cormer of the slot where the wire pressed against it.

I then painted the wires with nail varnish in the hope that this would repair/maintain the insulation, and then lay insulating tape between the first three wires which I pressed back into the slot. I didn't bother with tape between the remaining wires because the lacquer on them seemed OK, and there wouldn't be room in the slot for that many layers. Even then it was touch and go that everything would fit back in. There is very little clearance between the field coil and the rotor, so everything needed to be flush.

As the wires had been bent outwards when I lifted them out of the slot, I had to hold them in place with small cable ties, for which there was just enough room. The second picture shows this.

After a few reassemblies, I was happy that I had everything fitted correctly and that the surplus edges of the insulating tape were trimmed back enough to avoid any rubbing.

I then refitted the alternator to the car (I am getting quick at this!) and started it up. At first I though it hadn't worked because the ignition warning light didn't go out, and the rev counter didn't function. After a few seconds both returned to normal, and were fine on subsequent restarts. The grinding noise has also gone!

It remains to be seen whether this will be a permanent repair, and I do wonder whether the water was the cause or whether this was just a coincidence.

Anyway, I have gone into some detail here in the hope that this might help someone else.

Many thanks to all who took the trouble to reply, and especially Datatek for setting me on the right lines. It's just a shame that this problem prevented me from going to Sibbertoft for Pay & Play today!

Happy New Year everyone!

Pete

Pete The Biker said:

Well, more investigation today, and Datatek gets the prize for the best reply! - Thank you very much!

I started the car again today and unlike Friday, this time there was no life from the alternator at all (last time it would work if I rev'd up), and no noise!

So on the basis that I had replaced everything else in the alternator recently, that only left the coils to check. A few minutes with the multimeter confirmed that there was indeed a short from the wires in the field (static) coil to the frame.

So, the problem was identified but where was the fault? I gave the coil a good clean with a toothbrush and warm water to get the mud off (not a lot really, it was dirty rather than caked with mud) so that I could see what was what.

The only place I could see a possible fault was on one of the wires where it looped round into one of the slots in the frame - it looked like there was a little bit of spark damage. It wasn't easy to see because it wasn't the top wire, and all the wires were hidden under one of those cardboard(?) inserts which hold the wires in some of the slots.

On the basis that I had nothing to lose, I thought I would have a go at a repair, although to be perfectly honest I didn't hold out much hope.

So, the first step was to very gently prise out the cardboard so that I could get at the wires, and then one by one lift them out of the slot so that I could examine them. The first picture shows the wires lifted out, the lack of lacquer insulation on the second one up, and the damaged insulation on the edge of the slot. It looks like the insulation had broken down just on the cormer of the slot where the wire pressed against it.

I then painted the wires with nail varnish in the hope that this would repair/maintain the insulation, and then lay insulating tape between the first three wires which I pressed back into the slot. I didn't bother with tape between the remaining wires because the lacquer on them seemed OK, and there wouldn't be room in the slot for that many layers. Even then it was touch and go that everything would fit back in. There is very little clearance between the field coil and the rotor, so everything needed to be flush.

As the wires had been bent outwards when I lifted them out of the slot, I had to hold them in place with small cable ties, for which there was just enough room. The second picture shows this.

After a few reassemblies, I was happy that I had everything fitted correctly and that the surplus edges of the insulating tape were trimmed back enough to avoid any rubbing.

I then refitted the alternator to the car (I am getting quick at this!) and started it up. At first I though it hadn't worked because the ignition warning light didn't go out, and the rev counter didn't function. After a few seconds both returned to normal, and were fine on subsequent restarts. The grinding noise has also gone!

It remains to be seen whether this will be a permanent repair, and I do wonder whether the water was the cause or whether this was just a coincidence.

Anyway, I have gone into some detail here in the hope that this might help someone else.

Many thanks to all who took the trouble to reply, and especially Datatek for setting me on the right lines. It's just a shame that this problem prevented me from going to Sibbertoft for Pay & Play today!

Happy New Year everyone!

Pete

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Alternators do not like water. Specially if they are hot. Think if you look at the packaging on a new one it will say, warranty void if it has been in contact with water.

Brill news Pete, and a great post....as you say, might just help someone else!

Fingers crossed, let's hope the bugger behaves now!

crap on the belt like you say, is there a tensioner on that belt?

fett said:

crap on the belt like you say

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No - I am convinced the noise was internal to the alternator.

On Friday the alternator was making the noise - I didn't touch it again till today when the noise had stopped, and the alternator had failed completely.

In the meantime I hadn't touched the belt or anything else.

Pete

sorry, I posted that after but opened the page before your conclusion/reply was on there lol.

Good to see the repair, I hope it works long term. Plus I know who to go to for alternator removal and refitting at F1 speed now lol

fett said:

sorry, I posted that after but opened the page before your conclusion/reply was on there lol.

Good to see the repair, I hope it works long term. Plus I know who to go to for alternator removal and refitting at F1 speed now lol

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No problem Fett. I certainly feel like I know my way round the insides of the alternator now, having worked on or changed everything except the casings!

By the way, I got the refurb kit off ebay - including regulator and brushes, slip rings, rectifier and bearings, for £21 incl. postage. Great service from seller 8617petert.



Pete

Good post! Good explanation of problem & cure with good piccies.

Pete The Biker said:

No problem Fett. I certainly feel like I know my way round the insides of the alternator now, having worked on or changed everything except the casings!

By the way, I got the refurb kit off ebay - including regulator and brushes, slip rings, rectifier and bearings, for £21 incl. postage. Great service from seller 8617petert.



Pete

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I will bear that in mind but I hope I never need it lol