M1028 charging problem

[Keitho]

ok so I was driving home from work and my gen 1 light comes on no problem still driving. I go to start the truck the next day and batteries dead as expected. I figure the alternator went bad so replaced it with the autozone one that was in there before. truck was running fine for about 5 mins then gen 1 light came back on. I thought that maybe the alternator I got was junk so switched it out with another but the same thing happened. any ideas what the problem could be. and I notice that the hot wire on the alternator is putting out 55 volts and keeps popping a fuse that's in the hot wire. could it be relay?. electrical is definitely not my cup of tea.

any help is greatly appreciated.

-Keith

 

[doghead]

Which side alternator is your problem?

Where are your leads when you measure 55 volts? Is your meter set on DC voltage?

 

[Keitho]

Driver side alternator. I put the leads on the hot wire in driver side alternator and the ground on the bolt on alternator. and yes its on DC voltage. I was just out there and changed the fuse, the truck ran good for 20 mins and alt. was putting out 14 volts until I shut it off and started it again. the alt. started putting out 55 volts again

 

[doghead]

Never seen this before.

Perhaps a voltage regulator could cause this, maybe?

What brand of alternators are these?

What part number?

 

[Keitho]

I believe the original alt. on passenger side and the DL7157 autozone on drivers side.

 

[doghead]

I don't know.

Return it and request it tested?

 

[Keitho]

that's the weird thing about it I returned the first one for same issue and had them test that and they said that one was fine, but I exchanged it anyways. now its doing the same thing to the alt. I just got.

 

[doghead]

I can't think of anything that could cause it elsewhere on the vehicle.

 

[sneekyeye]

This may sound weird, but you could heat up that one alternator with a hair dryer good and hot, and start it to see if when the alternator is hot the voltage regulation fails in some way. This of course isnt going to help your fuse blowing situation though.

 

[Keitho]

would the voltage regulator in either alternator cause the driver side alt. to overcharge?

 

[sneekyeye]

Perhaps its something so simple as a short in the positive wire between the alternator and the battery causing the fuse to blow. The regulator thinks the battery is at zero volts all of a sudden and maxes itself out trying to charge.