Alternator Fault?

[Henry]

My early S2 2.1 TD decided to show me its alternator light on Sunday-came on for about 30 seconds or so while driving, the climate control panel flickered on and of for about 5 secs and the radio 'chattered' too then as I was accelerating up a shallow hill the box changed down and the light went out and stayed out for the remainder of the journey. Started the car up last night and all was well.
Tonight start of journey ok-then light came on and I noticed that the climate panel was off as was the heated rear screen, climate control panel flickered for a while then was on then off...all the while the alternator light was on. Each time I restarted the car ( lots of short journeys) the light stayed off for a while-5 mins or so then came on with the associated on / off of things, on the final journey home ( of about 35 mins) all was ok-climate was ok heated screen ok (even the suspension which had gone to hard had returned to comfy mode).
Now I suspect the the 'engine running relay' had been dropping in and out to cause the climate-screen and suspension (?) problems but what would cause it? Surely if the alternator had packed in then the alt light would be on permanently? Or could it be the ignition swith-although car starts ok? Or just a faulty engine running relay-but would this bring on the alternator light?
Next question is- if it is the alternator what models of XM and series1 too?- are interchangeable?

Many thanks in anticipation....

Alan.

PS the car has done 176 000 so I'm not annoyed by the failure-I just want to fix it!

[terry g]

could be the brushes in the alternator, the heater/climate relay,could be voltage sensitive so when the alt stops working the drop from about 14V+ to just over the battery,s 12V could cause the heater to switch off,??? .next time the alt light comes on get someone to clout the alt and see if it goes out? if it does then its pobably the brushes or a connection?

[onthecut]

Hi Alan.

I'd say Terry's assessment is spot on. The climate control and HRW are both no-go until the alternator kicks in --- and at that mileage it's entitled to be getting a bit temperamental.

Mike.

[Peter.N.]

Hi Alan

When the fault is present check for the 14v across the battery, much less and you have an alternator problem - but first, check that the belt is not slipping!

Peter.N.

[Henry]

Thanks guys-you've confirmed what I thought was probably so! I don't think that the belt's slipping-there's no squealing any how! How's about compatability with S1 and other models?

Alan.