Alternator caught on fire- Help Please!

[Hiliner222]

has anyone seen this before. I know a little bit about my engine (replaced water pump, starters, fuel pumps, etc) but have not seen this before. On Saturday I replaced the ignition coil on my 1998 Mercruiser 4.3LH. Put the muffs and started her up. She fired up immediately, after approx 45 secs I noticed smoke coming from the inside of the alternator. I shut it down shortly after that so the motor never ran longer than 1 min total. Anyone seen this happen before after replacing a coil? Do alternators just "let go" in this manner? I followed the OEM manual correctly and double checked the wiring to make sure I did not reverse polarity on the coil before firing up. Everything was as is should be. What happened? Thanks in advance.

 

[littlebookworm]

Re: Alternator caught on fire- Help Please!

What comes to mind quickly is that you have one wire on the coil connected incorrectly and have grounded out the alternator, shorting it out. I'd suggest you triple check all the coil connections. Unfortunately, that alternator is probably toast; but before you buy a new one, have it checked out at an alternator shop. You may have just burned the diodes, which can easily be replaced. Good luck and let us know what you find. Hy

 

[Hiliner222]

Re: Alternator caught on fire- Help Please!

Thanks littlebookworm for the reply. I did check the wiring on the coil before start up. Also verified in the OEM manual the color of the wires. Gray for the neg and purple for the pos. The only other wire is the center one that carries the load to the distributor. Have you ever seen an alternator let go like that- anyone?

 

[Silvertip]

Re: Alternator caught on fire- Help Please!

Alternators die for any number of reasons. Brushes wear out, diodes break down, windings short, bearings fail, etc. When things fail is another variable. They may fail as in your case, they can fail at high rpm due to windings coming loose, and they can fail at idle. In other words, alternators can fail at any time, under any condition.

 

[Hiliner222]

Re: Alternator caught on fire- Help Please!

Thank you SilverTip- was trying to confirm if that were so. I have been having a number of "gremlins" with this motor this year. Seemed strange that within less than a minute from installing a new coil that the alternator would "Blow up". This looks like a case of ***** happens.

 

[waterone1@aol.com]

Re: Alternator caught on fire- Help Please!

In my opinion, there isn't any-way that a coil replacement would "cook" an alternator. I don't care how you wired the coil. To put it another way, even if you shorted out the coil wires, the engine would not start and either a fuse or wire would burn-up long before the alternator was smoking. You would either have to directly short the output of the alternantor while it is at "charging speed" or feed voltage at the wrong polarity back to the alternator in excess of the diodes PIV ( peak inverse voltage).

 

[Hiliner222]

Re: Alternator caught on fire- Help Please!

Thanks WaterOne- so if i understand you correctly- it was not the addition of a new coil (or a bad 2 wire job on my part) but just the natural expiration of an alternator? I feel better now and will be dropping a new alternator in this weekend- wanted to make sure before I spent 2 benjamins on it.

 

[Splat]

Re: Alternator caught on fire- Help Please!

Well hell there's your problem, you let the magical smoke out of it. Nothing electrical works without the magical smoke.

Bill

 

[Silvertip]

Re: Alternator caught on fire- Help Please!

Don't be so hasty about installing a "new" alternator. Every city has at least one auto-electrical repair facility that specializes in rebuilding alternators and starters. Alternators can usually be rebuilt cheaper than new (unless it is truely trashed).

 

[Hiliner222]

Re: Alternator caught on fire- Help Please!

Good idea Silvertip- never thought of that- will check into that today. Will let you know if I was able to save any money.

 

[Hiliner222]

Re: Alternator caught on fire- Help Please!

silvertip- only checked with one repair shop for the alternator. Got a quote for $135 repaired and $175 new. It is a 40 min drive, I may just get new closer to home. Thanks for the thought though

 

[tashasdaddy]

Re: Alternator caught on fire- Help Please!

check all your wires for a bare spot, that could be shorting to the block, or bracket.