Practically Classics Forum

Hi, does anyone have any recommendations for an alternator upgrade for a 1750 alpine? If the car is driven with the lights on the battery goes flat.. the alternator has been rebuilt but the output still isn't enough
Thanks for your advice

How old is the battery?

And check earth cable points.

I can't help with an alternator upgrade, but my immediate thought is that assuming that the car is roughly standard (i.e. no accessories that draw a heavy current) then the stock alternator should be more than adequate, therefore there's something wrong. We need to know more - is the car standard? What are the voltages across the battery a) when everything is switched off b) at tickover with nothing else switched on c) at 2000 revs, d) at tickover with the lights on and e) at 2000 revs with the lights on. This will tell us a lot about the likely cause of the problem.

Who "rebuilt" the alternator, and exactly what was done? Is it the stock alternator for the car?

Cheers!

Thanks for your help, from what I understand the car has been restored professionally and the alternator has been restored by the local specialist.. I'll have a word with the mechanic/ body work chap tomorrow and ask.. he's a good mechanic, I've seen stuff he's restored before from alfas to Morgan's etc found the oil leak on my galaxy in the time it takes to open the bonnet..

Sounds like the chap who renovated the alternator didn't do a good job..

A bit of a long shot, but is the alternator body properly earthed? On my Rover, the alternator bracket is mounted on rubber and needs a separate earth wire, otherwise it goes haywire. A good battery will show about 12.5 volts with the engine stopped and nothing switched on. AT 2000 rev/min with the lights off you should see 14 to 14.4 volts and this should only drop by about 0.4 volts when you turn the lights on. I am assuming this is the modern fastback Alpine, the sports car would be positive earth and have a dynamo.

suffolkpete wrote: Fri Aug 09, 2024 9:07 am I am assuming this is the modern fastback Alpine, the sports car would be positive earth and have a dynamo.

That's a good point, I'd assumed that it had an alternator from factory, but if it originally had a dynamo and someone has converted it, I suppose it's possible that they've used an alternator that isn't man enough. However, I doubt it, an alternator that can't cope with the current draw of headlights is a pretty sick alternator, so I still stick to my theory that there's something else wrong. More to go wrong on a conversion though, one has to take into account the knowledge and competence of the person who did the conversion.....

Agree with Pete's comments on the voltages that you should be seeing.

To be honest, if the guy who reconditioned the alternator is the same guy who is having the problem then I'm questioning his competence here, as measuring these voltages and coming to a likely diagnosis is pretty straightforward, and should be child's play for a professional. Difficult for us to do at a distance though, especially as it's not your car.

Thanks for the advice, I will pass it on