Alternator Burning ?????????

[neilmw]

92 4.3l merc' alpha gen ll

Boat has been out of action for a while as I didnt use it much over the winter and have recently fitted new manifolds, elbows etc and also starter motor.

Since it has been running I noticed that the battery meter was showing between 15-16volts when running and slightly less at idle. I was also getting loads of squealing from the alternator belt. This was also confirmed using a meter on the battery.

Went for a short blast this morning and after a few minutes noticed a real bad smell of burning plastic, I slowed down and checked all around the engine and could find nothing untoward, I carried on back to the marina and noticed there was no noise at all from the belts and the volts were static at 12v regardless of speed. I was fairly sure it was due a new alternator before I went out but was puzzled by this smell, could it be that something had burnt out in the alternator causing this smell ???

 

[getinmerry]

Re: Alternator Burning ?????????

You didn't provide much info an engine type etc., but it sounds like the regulator crapped out. Seriously dangerous problem though. Make sure you get to the bottom of the problem before using it again.

Chuck

 

[neilmw]

Re: Alternator Burning ?????????

Yea forgot the basics, so could the smell have been caused by the alternator ?

 

[mkast]

Re: Alternator Burning ?????????

On the muffs or at the dock, measure the voltage of the battery with the engine off using a digital volt meter. Start the engine, measure the voltage at the battery again. Gauges are not very accurate.

 

[neilmw]

Re: Alternator Burning ?????????

Voltage at dock was 12.3, whilst running before the smell was 16.7, whilst heading back it was 12.1

 

[getinmerry]

Re: Alternator Burning ?????????

You still didn't post the info, but it's classic symptoms of a bad regulator. The regulator is in the alternator in most cases. However, at this point you may have baked the battery and possibly some other items. 16+ volts is too much for a battery for any peiod of time. 14.5 is typical high voltage for an alternator output.

Chuck

 

[getinmerry]

Re: Alternator Burning ?????????

Opps! Missed the edit on the original post. That would have the internal regulator.

12.1 volts limping back to the dock would tell me you were on battery power only at that point. The alternator had died.

Chuck

 

[neilmw]

Re: Alternator Burning ?????????

Thanks for the posts, I had guessed the alternator had gone, just wondered if there was anything inside the alternator that would have caused the smell, had a good look round the engine but could find nothing at all that looked as though it has burnt??

 

[Pierutrus]

Re: Alternator Burning ?????????

Thanks for the posts, I had guessed the alternator had gone, just wondered if there was anything inside the alternator that would have caused the smell,

The regulator/diodes are located inside the alternator. You can't see them unless you open up the alternator. Did it smell like something burning up on a circuit board?

 

[neilmw]

Re: Alternator Burning ?????????

It was quite a distinctive plastic burning smell

 

[Pierutrus]

Re: Alternator Burning ?????????

It was quite a distinctive plastic burning smell

Then that's what it is/was.

 

[neilmw]

Re: Alternator Burning ?????????

oh good, thanks for your help