Vixen 2500 Alternator Squeal

[yosini]

afternoon all,

Alternators should be quite straightforward but this one is puzzling me...I put a new one on the other day, tested the voltage and all was happy. Then I took it out just now for a first proper drive - all fine until about 20 mins in when it started squealing. First thought was I hadn't tightened up the bolts enough and it was slipping. The ammeter then started reading very high - peaking at max charge when only on around 2500 revs with lots of squeal. Then about 5 minutes of gentle driving later I stopped at lights and blipped the throttle, same thing, squeal and high ammeter reading. Then it stopped - just like that - ammeter back to normal and no squealing. I got to work and checked the tension in the belt - all was fine - I took it off to check the free spinning of the new alternator and also felt fine - it was pretty hot though - slightly hooter than the rocker cover - which seemed a bit strange. Anyway, as my voltmeter was at home I tested the ammeter reading with no belt and it was negative, and with belt on charging slight positive so thought all was well. Finally put it back together for a last check and it started squealing again! - same symptoms as before so I've left it for now and gone in search of internet advice and WD40 in case it's just a bit of a sticky new alternator....

Anyone any advice? thoughts?

Cheers

Joe

[Astacus]

First thought would be something come loose inside the alternator, if it's new and the belt isn't slipping.

Voltage jumping about is pretty odd though. I'd whip it off and take a look inside.

[Dollyman1850]

Try a different belt. some spurious belts can have a dodgy taper and the belt bottoms out on the pulley resulting is squeal even when it looks to be properly tensioned.

N.

[yosini]

the alternator saga continues....

so I (maybe stupidly?) squirted a bit of wd40 on the spindle and I have no more squeal. Great, however, I'm not sure the alternator is charging now (still not had a chance to put a voltmeter on it) as the ammeter sat around the slight negative all day with no sign of movement with the engine revs.

It did do around 300 miles yesterday and aside from that (and the other thing I'll mention in another thread to follow) perfectly....I'll report further once I've got a voltmeter on the battery.

Mixture of fast Motorway and very enthusiastic A road driving returned 29.2 mpg over the whole day which I was pretty pleased with.

Cheers
Joe

[Alpha Omega]

I think the Alternator was intermittently overcharging and causing a tightish fan belt to slip
I think that the Alternator has now stopped charging
Running the Alternator for any length of time in an overcharge state will have possibly burnt out the Stator windings and cooked the battery
I think that when the squealing had been going on for a while, if you had touched the Alternator pulley you would have burnt your fingers and this would have proved that the tightish belt was slipping on the Alternator pulley
I also think that thinking can be a dangerous thing, so if you visit back here and read about what I think please don't take it as gospel but do think about what I think

[Mr Tiger]

The alternator on my 2500 went haywire a couple of years ago. Like yours, the ammeter was showing a high +ve reading at around 2500 revs but returned to around zero at tickover. Unlike yours, there was no squealing. A new alernator sorted the problem. Perhaps the new one you have is faulty.

I was under the impression that lots of amps going through the dashboard wiring can be dangerous. Perhaps others can clarify.

Does your new alternator have the standard or more modern higher output by the way?

Good luck,

Chris