Alternator Noise

[chrisryder]

Howdy, this could be either electrical or mechanical... so i've put it in general!

I've got an 18ACR alternator on my minor, and an high pitched whistle/squeal is emanating from its general direction.

Seems to be most prevalent when drawing higher currents (lights on) and on tickover. As soon as i rev, it stops making the noise, and then as the revs subside it comes back!

I changed the fanbelt last week hoping that might be the answer (cheaper and easier to change the belt than the whole alternator!) but that hasn't cured it...

Is there any way of lubricating it, or do i bite the bullet and fit a new one?

[bmcecosse]

Make sure the pulleys are absolutely dead inline. Try to squirt a bit of wd40 into the general area of the front bearing... New bearings cost pea-nuts, so if nothing else works - try new bearings!

[chrisryder]

it's difficult to tell if they're inline. there is currently a washer between the water pump and the alternator to bring the pulley forwards to promote alignment. that washer was fitted when i last had the alternator off, which was when the front was off the car, so checking alignment was easier.

i could try removing the washer, which would put it back to 'as intended'. might work... and then i could try the wd40 if all else fails!

[mike.perry]

The new fan belt could have bedded in a bit and become a lttle slack and caused the squeal again

[bmcecosse]

Usually a thin washer is required. Mis - Alignment is normally easily spotted. In with the WD40! But don't get it on the belt......

[chrisryder]

hmm... i'll recheck the belt tightness and get merry with the wd40 then.

thanks for the advice, i'll report back with my findings!

[chrisryder]

a quick look in between other jobs today, and i found the alternator pulley turned easily, slipping the belt, so i've tightened that up. hopefully that'll do the trick. off out tonight so i'll be able to tell if it's worked with the headlights going!

i've just remembered i've got a good spare alternator lying around, so even if it is the bearings, i can always swap that over

[MarkyB]

Is the alternator pulley the same Vee as the dynamo was?
I had a problem with a mismatch between pulley and belt once that meant only the top edge of the belt was doing any work, it soon wore out and I think it screeched too.

[bmcecosse]

" good spare alternator lying around " - what use is that? It should be in the boot so you have it with you all the time - along with a good belt of course.

[chrisryder]

it went with me to france, along with the spare diff, but i don't take it everywhere! i've got free recovery for a reason

anyway, the squeal/squeak did go away briefly, but by the time i got home it was back to its old tricks of being fine when revving but noisy at tickover. i'll try WD40 next!

[chrisryder]

oh, and the good spare alternator might be coming with me to uni tomorrow, just in case the one fitted suddenly gives up!

[bmcecosse]

Carrying a spare diff - now THAT'S one up on me !

[chrisryder]

a few years ago someone on MOT blew their diff and nobody had a spare. they had to get one shipped out during the week!

ever since, we've always taken a diff, and never needed it!

it's silly everyone taking the obvious things. 100 spare coils are no use to you if your diff has gone!

[bmcecosse]

Well -it's 'NEVER' the coil anyway!! Does someone carry half shafts ??

[MarkyB]

I used to when I took my van.
I cant remember now if I supplied one to a traveler who broke one going from reverse to 1st when the car was still moving.

[mike.perry]

Back to alternators--An alternator drive belt has teeth on the inside circumference to allow for the smaller radius of the alternator pulley. Have you got the correct belt fitted?

[chrisryder]

my dad has a pair of halfshafts in the boot of his minor. it only goes to shows, and on MOT, so they stay in there full time.

two go very easily accross the back of the boot behind the spare wheel, without taking up any real space!

halfshafts are diff are not things you're likely to replace at the side of the road, but when you're in the middle of europe, needs must!

in alternator news, mine's still whistling away merrily, but it'll have to do for the next day or two. i'll put the spare on at the weekend and see if that cures the noise.

and yes, i've got the correct belt 'for alternator conversions' from my trusty local minor parts supplier.

[bmcecosse]

But - if you keep the spare half shafts there - where does the spare cylinder head go ?

[katy]

Whine in the alternator can be a bad diode(s), or a bad bearing, though not usually a bearing. Try changing the alternator out for your spare and see what transpires.

[bmcecosse]

The toothed belts are a disaster - use a solid belt......