charging system problem

[hdlowrydr85]

I have a 1988 omc cobra w/2.3l Ford. It has a motorola 4 wire alternator. This year has been a nightmare. To begin the year a new battery (expected) then a starter, next a few weeks later a new choke heater. Now for the last four weeks I have been chasing a charging problem, the boat runs great, the belt is new, the alternator drops back to battery voltage and quits charging at 4000 engine rpm, pull the throttle back to 2500 rpm and the alternator starts charging again. I have had the alternator tested by two very reputible automotive electrical rebuilders. Everything checked out fine. But still the problem. I gave up and purchased a new regulator, still no change. I have tried double circuting everything from the battery and still the same problem. A new alterator is a little more than $330 at the local dealer and the local auto parts stores cannot get one. does anyone have any ideas? Your help would be greatly appriciated.<br /><br />Thanks

 

[denniz]

Re: charging system problem

Ive found weird problems like this are usually a ground problem. Not always, but make sure you grounds are clean.

 

[hdlowrydr85]

Re: charging system problem

Thanks for the responses. I did forget to mention that the rebuilders opened it up and said everything looked like new. When changing the regulator, the brushes need to be removed and yes they looked great. I did notice the black carbon dust on the rectifier bridge and cleaned some of it off. My next move was to eliminate the boat from the alternator by jumping the alternator direct to the battery and tying in any other wires to make the boat run. I have also been using an external volt meter, not the one in the dash since the problem occured. It's not that replacing the alternator is so expensive, it is that I really would like to be sure what the problem is first.