Duramax alternator

Anyone have problems with one or familiar with common issues?

Dad's '04 d-max is giving him intermittent alternator not charging message. Probably going to pull it tonight have it checked and probably replace it.

When he checked it, it read 14 volts, but the light had also gone off at that time. Im thinking the regulator on the alternator is probably on the fritz.

Thanks for any help, unless I learn something else im going to have the batteries and alternator load tested and replace what aint working.

Don't waste money. Check thoroughly for loose or corroded connections. That regulator is usually go or no go.

The brushes are going bad. Mine did same thing

I had plans last night so told him to check battery connections and connections at alternator. He said some corrosion at batteries cleaned and all had good connection and light was still on this morning.

Surprisingly they aren't that expensive haha.

Thanks for the advice wanted to see if there were any common problems. Its got a bit over 200k on it so it doesn't surprise me the brushes are worn.

definately replace - if it is the original with 200k on it; dont wait for bearings to go out (next) !

do the belt(s) and idler/tensioner too (if original) while you're in there - they won't be far behind if orig.

Its the original alternator, but belt etc. has been changed per normal maintenance, think its only 6 mo old. Batteries are 3 years old so they probably don't have long to go even thought they still read a full charge and crank with no issues.

If you have a local auto electric shop let them test the alternator for you.

Had it tested at two places both said everything checked out in spec...

Back to the drawing board, looked up some info on trouble shooting it with a volt meter and think we have a problem on the ground side somewhere, which may explain why the problem was intermittent. Put it back in after testing cleaned and tightened all connections and will see if it comes back. If so we will be looking for corrosion, breaks etc in the ground side.

Batteries tested individually and disconnected from the system read 13.14 and 13.13 volts, so it is doing its job at keeping the batteries hot, hopefully we just had a bad connection, but nothing seemed to be loose etc. Thanks for the help.

matt

Keep us posted on the outcome with this please. Typically when you get the message on the drivers information center you have an diode issue and it can come and go for a while. It could be good and bad if you have a terminal tightness issue at least until you find it....

Matt, this could be an instrumentation failure. The ECM is starting to appear on the horizon. Ground wires can be the culprit, too. Check where batt and ground connects, usually to the block. If so, then you have another cable connecting the block to the firewall (dated info). Maybe your meter set to ohms, connect one lead to alternator housing, other lead to frame. Look for zero ohms, then start moving stuff around. Then get the meter leads out of the way and start it. Watch the meter, it should not waiver.

You're past the easy stuff now buddy. Good luck.

One person I talked to said the voltage regulator on this truck is controlled by the ECM not internal to the alternator and could be the ECM is about to take a dump... sure hope that is not the case.

It was giving him the code every time he drove the truck. We pulled it out had it tested cleaned all connections and put it back in. Drove it to dinner and back last night and to work again this morning and it has not come back on yet. Fingers crossed it is resolved, but only time will tell.

He drove the truck till this weekend with no lights so about 2 weeks. Light came back on when they started it to leave our house Saturday and once they got home it wouldn't start. Batteries read 12+ volts with motor off. Wouldn't not crank the truck though, jumped it and they read 9 volts(running). Took alternator in to be tested again and it failed every test. Charged batteries put in new alternator and no lights... lets hope it stays that way!