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4023 Alternator isolated ground

PostPosted: Thu Jan 26, 2012 9:11 am
by MollyBlossom
I have one of your 4023 alternators with isolated ground. I have had to replace all the rectifiers three times in less than a year. The unit was drawing about 85 amps before burning out the rectifiers. The last set that was removed the wires were black. The time before the solder had melted. I think the problem is that the heat sink with the rectifiers cannot conduct heat to the alternator case, so that the rectifiers are probably 10 to 30 deg C above the case temperature. Do you know what that differential temperature between the rectifier heat sink and the alternator case? It should be designed so that the rectifier heat sink couples the heat to the alternator case similar to the way a audio power amplifier is designed. I am not sure that I can get 70 amps out now for an extended period.

Re: 4023 Alternator isolated ground

PostPosted: Thu Jan 26, 2012 12:31 pm
by Coulomb
The alternator case isn't involved with cooling the diodes. It does help to cool the stator.

I'm guessing you have an air flow issue. Is the alternator mounted normal to the engine? Mounting it forward of the engine without a bidirectional fan will result in overheating that you are having.

Air flows from the rear of the alternator to the front. If the fan is rotating the wrong way, no air flow, overheating.

Re: 4023 Alternator isolated ground

PostPosted: Sat Jan 28, 2012 12:50 pm
by MollyBlossom
Is there a way I can send you a picture of how it is mounted on the engine and show you the direction it is turning?

Re: 4023 Alternator isolated ground

PostPosted: Sat Jan 28, 2012 7:11 pm
by Coulomb
You can upload a picture in your reply.

Re: 4023 Alternator isolated ground

PostPosted: Mon Jan 30, 2012 9:24 am
by MollyBlossom
Looking aft at the alternator pulley it turns clockwise. This alternator is not yours but a spare while replacing rectifiers in the Ample Power alternator. The picture shows how it is mounted on the side of the engine. You can see the front of the engine with the large pulley on the engine and alternator

Re: 4023 Alternator isolated ground

PostPosted: Mon Jan 30, 2012 5:34 pm
by Coulomb
Make sure that air is being pulled from the read of the alternator and thrown out at the sheave end.

Re: 4023 Alternator isolated ground

PostPosted: Tue Jan 31, 2012 11:48 am
by MollyBlossom
The pulley rotates CW as you face the front of the engine, which is what you recommend.