'powdering' of alternator belts...

[Pants]

I thought my old alternator was toast (after all, it was 15 years old), but a brand new one is doing exactly the same thing: the belt is snug (and only a month old), but my system is barely charging, or not charging at all, but the belt is squealing and heating up the pulley at moderate RPM, as if it's really working hard...and leaving a steady accumulation of belt-powder around the general vicinity. I replaced the old belt recently because it had become too worn to put tension on it within the confines of the adjustment. My voltage never gets above 12.8-ish. Brand new battery - a few days old - still starts fine, but is not getting charged much if at all. Ign lite either dims, or stays on full brightness, regardless of RPM. There's no visible drop in headlight brightness when the engine is switched off.

But from the squeal and heating of the pulley, it's like the alternator is being taxed heavily, the charge being dissipated in some invisible load-bank. I've retensioned the belt a number of times, and each time am greeted with more squealing. And no, it's not OVERtightened, either. So where's all that energy GOING?

Since I can't think what else to do, I'd like to make temporary bypass connection/s to the new alternator, now in the car, so as not to assume anything about my existing wiring. I've always run the previous alt (this one's a Lucas 45A replacement for 16ACR and 17ACR) on two wires only, and this model has only two connections (see photo)

so it should be simple to test in situ. Can someone please confirm, then, that to test the basic functions, I might wire/test as follows:

1) run either fat (wide quick-disconnect lugs) brown lead to +12VDC
2) run small brown/yel lead, connected through an auto test-light, to +12VDC

Testing:

a) with power in place as above, and engine not running, test light should be ON.
b) with engine running - and perhaps RPM revved up and then kept up a bit above idle - test light should dim and go out, and voltage on fat brown lead should be somewhere in the range of, say, 13.5-14.5V
c) With belt snug (about 1/2" up/down play with pressure from thumb on belt), no squealing should be heard.

What else could be the problem?

 

[jon small]

before going to the trouble of running temporary wiring etc first check earth strap connections to body and engine and battery connections as this sounds like a high resistance at one of the connection points.try a jump lead from battery earth to alt casing.
if you try the temporary wiring set up also run a lead from earth terminal of battery to the alternator body as some alternator mountings have rubber bushes and need an earth fly lead and have come even across solid mountings that had a poor connection to engine block,
good luck and let us know how you get on - jon

 

[Ib≤In≤Iz]

I would be investigating the squealing first tbh, check all the pulleys/bearings are ok. Is it tensioned correctly?

 

[ifindoubtdont]

It sounds very much like you have a seized or out of line pulley somewhere, as Ib says check all the pulleys and bearings first.

 

[telectrix]

years ago, had similar problem. a new belt got chewed up in 2 days. seized bearing on a pulley.

 

[Pants]

Thanks, guys...I'm going to go flog away at this some more later today...
(jon small): I was thinking along the same lines about grounding/earthing, but I get less than an ohm resistance from alt case to ground strap (to the stranded copper itself, which runs directly to the battery in the boot), and there's no hesitation or laboring while starting...so testing and the starter-motor seem to be telling me that battery connections are both OK. Still, it's an easy check, so I'll try that, as well as the direct-to-alt grounding. There are no visible insulators on the alt, though, and the resistance to ground-strap as I mentioned is almost nil.

Belt/pulley issues? This couldn't be a simpler setup - it's on a 1960 Austin mini - and so the belt touches only the crank, water-pump, and alt. The water-pump spins freely and runs as true as could be required of a belt-drive component (I've checked it twice while futzing with the belt, something I've done many times now). Aside from belt-squealing/powdering (note the powdering is definitely not from any bearing) the other symptom is the heating: it takes but 30 seconds of squealing-belt operation at, say, 2500RPM, for the alternator-pulley (and ONLY the alt pulley) to be uncomfortably warm to the touch. Yes, the pulley alignment is slightly off, by perhaps 1/16" (for some reason the new alt had different geometry and my attempts to shim were not quite perfect), but rather than focus on this side concern, it's more of concern to me that this is EXACTLY the same behavior as with the previous alternator: squealing, intermittent charging leading to no charging, powder buildup, eventually a loose belt needing to be replaced because there's no more adjustment range.

As for over/under-tightening of belt: 1) overtightening wouldn't cause squealing, nor such immediate overheating (nor was the belt overly tight); 2) if I'd indeed actually overzealously tightened the belt on some occasion, it wasn't that way the next, since squealing + heat yield rubber-powder + loose belt. This is the second belt/alternator that have done this on the same car - thankfully not my daily driver - since November.

Wits end on near horizon.

More on that previous alternator: not that I trust one of our ('yankee,' but Hawaiian-style) auto-parts shops to accurately test a Lucas alternator, but I brought the old one in to my standby domestic parts shop yesterday, and...yep, they say it's good. Chances of a false POSITIVE in that test seem small to me, but I will take it to a specialty rebuilder to test before I make a conclusion.

One way or another I will fix this and post back - please let me know of any other inspirations.

 

[ruston]

Have you converted this Mini from a dynamo?

 

[Pants]

Have you converted this Mini from a dynamo?

Yes, but that was in about...1982...? Been running on a Lucas rebuilt alt for many years since then - only recently replaced due to still-present problem.

--Dave

 

[ruston]

Yes, but that was in about...1982...? Been running on a Lucas rebuilt alt for many years since then - only recently replaced due to still-present problem.

--Dave

Is the pulley new with the new alternator ? If not check that the Vee is not coated with burnt belt, this will cause the belt to slip and squeal.

 

[R G]

Another thought , is the pulley from the old dynamo , it could be the pulley itself needs to be a larger diameter , this would allow less strain on the belt I'm sure ...