alternator overheating?

Your battery would have probably melted and caught fire before your alternator failed in that situation.

If your battery is holding a charge, your alternator is not damaged.

Er, has it fried or not ?

Have you fried your alternator ?

In the same sort of situation I wrecked a battery. If you're having problems are you sure its not that?

Ohh nono my car's errmmm fine I guess. I've been driving for a few days and still no probs so I suppose the alternator's still charging the battery. Anyway my question was, would the load of the diesel engine's starter motor have friend my alternator?

Thanks.

No. The alternator is regualted by the errr regulator (!) to provide a maximum output- say 55amps. When it reaches that figure, thats it.

If its burnt out- then it was going to do so anyway...

Tim..

Actually there is no current regulation, only voltage regulation. Set to about 14.0v to 14.4 on modern alternators. The lower the battery voltage goes, the bigger the difference between it and the alternator. This determines the charging current. So a little 35 amp alternator would try to provide 70 amps (if it didn't burn out in the process!) if you took 70 amps from the battery for a good few minutes because ohms law (we cant break the law can we!) says so...

I saw my old ford cortinas alternator smoking badly once after towing a caravan, that had loads of stuff turned on inside along with a bunch of 100 watt spots on the front of the car...

I turned them off and apart from smellling funny it still worked though.

The battery itself has a far lower resistance than any starter motor. If you think about it, it has to to operate a starter.

No, it would fry the jump cables instead.

Apparently >Ohh nono my car's errmmm fine I guess. I've been driving for a few

Yeah you're right. It's not so easy to regulate current. But I thought a 35amp alternator could only provide UP TO 35amp MAX? Will it force itself to generate more than that? I suppose in the end it's possible if there's no regulation of any kind coz at the end of the day the current/voltage output will go up as RPM goes up.

Yes it will try... But it will get very hot and bothered! As rpm rises the alternator gets more cooling too so it can do better than

This 35 number is a "nominal" figure anyway...

This always reminds me of a 'road trip' in the US with a rather knackered '73 Buick LeSabre with a huge V8. It's alternator was a little duff so we were always getting jumps from people (have you noticed that nearly everyone in the US used to carry jump leads!). Anyway this kind guy is a SUV stopped once and only had a length of speaker cable, being a Physics student at the time I was a little worried about this but he insisted and hooked it up. Turning the key on the Buick and amazingly she started, but in the process burnt off all the insulation of the "jump" leads which promptly burnt into the wing of his SUV shorting the battery out!

Will

Speaker cables? LoL. but that depends, some high end speaker cables can be 8 gauge, some amplifier OFC power cables can be 4 gauge. wow that's larger than more jumper leads. Only thing is, speaker cables aren't that flexible and their insulation can't take the heat a jump lead's insulation can take.

Anyway mine was 2gauge welding cables. no way they'll melt even with the biggest diesel engines.