Rectifier problems

[guy74]

I have had 2 rectifiers go bad on my 1988 60hp Johnson in less than 50 hours of operation. I don't know the history of the 1st one but I replaced it with one from sierra. It went out last night, melted the potting out of it, and quit charging. The voltage hads been kinda high for a while 17+ volts. Tach started acting weird for a little while then went back to normal when the charging system quit charging. I would like to figure out why it went bad, so maybe the next one won't go out because of something else.

 

[Molaker]

Re: Rectifier problems

Possibility - On engines without a voltage regulator, the battery acts as the regulator. This works because the charging current is fairly low and won't overcharge the battery. But, if the battery connections are dirty or loose, the charging voltage won't be held down by the battery and it can go high like yours did. This can create an overload for the rectifier.

 

[tashasdaddy]

Re: Rectifier problems

check the engine faq forum, 2 good threads on rectifiers.

 

[F_R]

Re: Rectifier problems

Bottom line is that rectifiers are most often damaged by reversing the battery polarity or loose and/or dirty connections somewhere between the rectifier and battery. Disconnecting the battery while the motor is running is another common no-no. If there is an interruption in the charging circuit (connections), the voltage on the rectifier shoots way up out of sight, beyond the breakdown voltage of the diodes and poof! It can happen in an instant. Or less.

 

[guy74]

Re: Rectifier problems

the battery connections have never been reversed since I have had it. All the connections are clean and tight. I'm gonna try a new battery and hope that cures the problem. The battery that was in it was 2 years old, guess it could be the cause. Thank you for the replies.

 

[guy74]

Re: Rectifier problems

Well a new batery and rectifier didn't cure the problem, I guess the stator is bad, it has melted potting dripping off the stator. What should I look for that would cause the stator to go bad? I think it was damaged before I bought the motor, had some potting dripped off it when I got the motor. Now it smells burnt. The tach was still working when it first stopped charging but tonight the tach was erratic then stopped working.

 

[F_R]

Re: Rectifier problems

Some stators have that problem without any cause. Just poor design/materials. However, a blown rectifier can cause it too by feeding battery current back through the windings and overheating it.