Alternator squeel

[akuchanny]

I have a new uprated alternator fitted to the car, but when the electrical load is high the alternator squeels, its just the same sound of the belt slipping. I have checked the belt it is correctly fitted and tensioned with around 1/4 of an inch deflection on its longest run, but when I turn off electrical items such as the heated front screen, or rear screen, radio or lights the squeel stops. If left the sound is horrible and the belt gets shredded whilst making a burning smell.

I've checked the connections all looks fine, and the belt tension is good, could it be a faulty alternator unit? Or possibly is it out of line with the pulleys so the belt is getting snagged under a larger electrical load?

Thanks in advance.

Andy

[kennatt]

if you are sure the belt is tight,then highly likely to be out of line,very often they are ,and need shimming to make the pullys line up

[lambrettalad]

Too tight?

[bigjim]

is the belt wide enough to give good grip in the pulleys , are the pulleys the same groove section , the original belts were a little skinny so fatter belt maybe the way to go

[MarkyB]

As above, not all belts are the same, also if it's running at the bottom of the pulley it wont grip properly.
The burnt surface of the belt you have now is unlikely to grip well
I've had "modern" cars that have this tendency, the answer can be to lower the revs until the squealing stops then raise them gently to maintain grip.

[bmcecosse]

I suspect the clue may be in the 'uprated' alternator.... Why uprated?? The alternator is likely drawing more power than the belt can carry... It is worth checking the alignment (as mentioned above) but if it still keeps slipping, you need a 'normal' alternator. Or - go to a modern car type multi-groove belt, although sourcing the pulleys could be tricky!

[akuchanny]

Thanks guys, just to follow up it's a small Lucas unit. I'm running a new quinten hazel belt at the moment same size as I have alwas run with no problems, can't remeber the part number off the top of head, , I have been dropping the revs and building gently to drive it at the moment, but also shutting everything I can off and then turning it back on as when mivung off frin a stop it always screeches when the revs rise. I will see if I can move the alternator more in line when I've got some time to play in the engine bay. As i hacent checked this yet, (it was instalked by a well known 'specialist' so they could have no doubt caused issues) I will also check if I have over tightened it.

I'm running the alternator as the car has Halogen lights, heated front and rear screens a hidden tripple 12v internal supply and a new stereo with separate amplifier and hideen powered sub speaker (not my idea, the girlfriend wanted to be able to hear her bad choices in music) as well as brake and coolant fluid level sensors, finally a third brake light unit into a mm badge's reflector space. So it's quite a higher power drain than original spec.

If there are any other ideas please let me know.

Andy.

[bmcecosse]

Halogen lights actually use slightly less power- unless you have illegal high power bulbs. The heated screens should never both be used at the same time - I don't do that even on my 'modern'. And even then - no more than 5 minutes and then off! They are not meant to be run all the time. The other power points you mention are almost inconsequential (unless a very high power amp) - so indeed the alternator should be able to cope easily with one screen plus lights. It is most likely a pulley mis-alignment problem.

[kennatt]

If it was a non friendly classic fitter,he would simply stick it on assuming that it would line up,They don't,and invariably need washers inserted to move the alt. in or out.Original was dynamo,with different fixing brackets,the fitter probably didn't know this so not really his fault,allthough he should check.

[MarkyB]

heated front and rear screens

Are you running them both at once? I don't think it's recommended.

[IslipMinor]

The standard V-belt section should not squeal with even an uprated alternator. I would suggest checking the pulley alignment and also the alternator pulley itself - does the belt fit at the top of the groove, where it should? If it is deep down into the groove, it is likely that it is 'bottoming' and will not get good drive that way.

Irrespective of maximum power output, an alternator will only put out what is required to cover the switched-on load, plus any charging requirements. We have a 55A alternator and some high powered halogen headlight bulbs + 2 x 55w halogen spot lights on with main beam. On a cold, wet night (i.e. heater and wipers) plus main beam, the current draw is about 40A, but there is no squeal.

[katy]

It might be the alternator itself, not the belt. Bad diode(s) in an alternator can cause it to squeel. You need to get it checked.

[bmcecosse]

Is the tail of the alternator properly supported on a 'long' bracket - or have they bodged it up with a long bolt/screw/threaded rod?? As Richard says - a standard alternator should easily run many lights etc on a standard belt. My Rally Elf with ACR 18 and many lights never gave any problems with belts.

[akuchanny]

Hi guys sorry I've been at work and only just got in. I dont run both screens at the same time, and do only run for a short time, I am going to fit a timer system to both so forgetting is never an option.

The garage is a "well known" minor specialist. I have a few bits to move out of the way to get a clear look at the fit, and will try to get to it this weekend. The belt does fit well in the pully, I havent checked the bottom yet as I haven't had the car up on a jack or ramps but will when I can.

I'm leaning to spacers / washers to put it in line, as the same specialist replaced the alternator with this one as they said the old one was shorted, although it did still charge. I guess the morale of the story is always fit your self, then there is only one person To blame, and you know what you've done to the car. Will keep you posted once I've had time to take a look.

[bmcecosse]

The old alternator was 'shorted' - but it still charged??? Strange story...... the plot thickens !

[akuchanny]

Exactly. I think they just wanted to charge for the unit. I left my farther in Charge as I was away. He has no idea about cars.

Had a quick look, looks inline but will check fully but tonight with lights and wipers squealing again!