BJ75 Electrical issue

[lynchmob]

1989 BJ75. 3BII with rotary pump and an internal vacuum pump rather than the alternator pump. 12V system.

A while back I started having issues where the lights would brighten and dim then the dash charge and filter lights would come on and off. Sometimes the charge and filter light are on all the time.

It was usually intermittent so I let it go for a long time.

Recently it flared up and blew the headlight and flasher relays. My thought at this point is that the alternator voltage regulator is fried and the relays were fried by an overvoltage situation.

I tested the voltage at the alternator today and it seemed in normal range or a bit high (high side was just over 14V). While testing I tried several different rpm ranges and it was fairly steady - until I let it go back to idle.
At the end of testing while at idle the voltage was lower at the alternator than it was at the battery(12.2 vs 12.4 ).

Right now I am assuming my only problem is with the regulator. Could there also be an issue with the charge light relay or some other relay??

 

[crushers]

take it in and get it tested??

 

[lynchmob]

take it in and get it tested??

I assume you mean the alternator and not the whole electrical system ?

 

[crushers]

yep...

 

[Ron R]

I tested the voltage at the alternator today and it seemed in normal range or a bit high (high side was just over 14V). While testing I tried several different rpm ranges and it was fairly steady

This is as it should be. A Max voltage of 14.4 V is allowable.

- until I let it go back to idle.
At the end of testing while at idle the voltage was lower at the alternator than it was at the battery(12.2 vs 12.4 ).

Right now I am assuming my only problem is with the regulator. Could there also be an issue with the charge light relay or some other relay??

I think the problem is in the alternator itself.
Probably one ( or more) of the rectifierdiodes is gone or there is some other short.
If you would bring it in for testing mention this drop and let them check for shorts against ground.

 

[lumpy70]

It's your brushes making intermittent contact. It happened to me.

Craig.

 

[lynchmob]

Well I did get the alternator tested and they said it was bad. It was putting out voltage, but failed one of three tests they do - they couldnt really explain what was wrong . They gave me a new one under warranty.

So I put on a new alternator. The charge and filter light did not come on when I started it, but the headlight and flasher relays blew again without me even turning either the lights or the flashers on.

When I check voltage at the alternator when the truck is running I only get battery voltage and there appears to be no output from the alternator.

Maybe they gave me a bad alternator, but Im going to start digging around to see if I can find any wiring issues.

Anyone have an alternator from a rotary pump 3B? The alternators Im getting at the local parts stores are actually for a 1989 4cyl gas pickup. When I first had to change this alternator about 4 yrs ago this one seemed to be a perfect match with the plug (and wiring of the plug).

Can someone confirm what alternator should interchange?

Thanks

 

[lynchmob]

Think I got it...

There are three fusible links (the wire type) connected to the battery on this rig. I found that one of them was broken at its connector. Seemed to be a mechanical failure. It was not blown just tweaked from vibration etc. Must have been coincedence that it broke the last time I reconnected the battery after installing the new alternator.

 

[Ron R]

Think I got it...

There are three fusible links (the wire type) connected to the battery on this rig. I found that one of them was broken at its connector. Seemed to be a mechanical failure. It was not blown just tweaked from vibration etc. Must have been coincedence that it broke the last time I reconnected the battery after installing the new alternator.

Wow, good you found this.
If this is the culprit than it's not very obvious. Lesson learned. Thanks for the feed-back