Possessed Envoy

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
Was out with the family today driving in the Costco parking lot when I felt a stumble and then noticed all the lights dimmed a bit. So the first reaction was to look at the tac and it showed proper rpm's. No dip and engine running well. Then I looked at the volts gauge and noticed it was low at about 12 or 13 volts. I drove the truck around for about 30 seconds and the alternator came back up to over 14 volts again. So to me this means I need a new alternator as mine is about to fail. Has anyone experienced this with our alternators?
 

shrek77

Member
Mar 30, 2012
252
Mine has done the same thing, a couple times a week I would say. Ive had it for over a year. I think I had noticed it about a month or so after I bought it. Doesn't bother me at all. Usually drops for a few seconds at like a stop light then back to normal. I'm not replacing it until never recovers lol...
 

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
But that's not good. Right? If this is any indication that the alternator is about to fail then you or I could get stranded at any time. So we should heed the warning and replace it ahead of time. Right?
 

shrek77

Member
Mar 30, 2012
252
CaptainXL said:
But that's not good. Right? If this is any indication that the alternator is about to fail then you or I could get stranded at any time. So we should heed the warning and replace it ahead of time. Right?
Mine has never dropped below 12v just enough to notice it. I'm not going to just replace it and it just be something that occurs occasionally. But that's just my opinion. Everyone has their own. Not that cheap to just buy a new one on a whim, but I agree it may fail sometime, but who knows.
 

gmcman

Member
Dec 12, 2011
4,656
Mine did that a few times and I wiggled the signal wire here (in pic) when it was acting up at it came back to life. Once I realized it may be the culprit I pulled the connector and sprayed some electronics cleaner in the connector and has been fine since.

Granted you will have a low voltage on startup on occasion allowing the motor to settle into an idle before the ECM engages the charging system. I trust this is not what you are experiencing.
 

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Dec 4, 2011
520
shrek77 said:
Mine has done the same thing, a couple times a week I would say. Ive had it for over a year. I think I had noticed it about a month or so after I bought it. Doesn't bother me at all. Usually drops for a few seconds at like a stop light then back to normal. I'm not replacing it until never recovers lol...

Mine does this in the winter, usually at a light when I am stopped. Not even a few seconds more like just a dip and then right back up. Usually happens when I have a high load, such as heater, heated seats, head lights on because it is dark. I always thought it was just the BCM just making an adjustment like it does on start up.
 

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
RedEnvoyDenali said:
Mine does this in the winter, usually at a light when I am stopped. Not even a few seconds more like just a dip and then right back up. Usually happens when I have a high load, such as heater, heated seats, head lights on because it is dark. I always thought it was just the BCM just making an adjustment like it does on start up.

Yeah, but I drove this truck a lot more in the past two winters and never notice it. I really think there is a problem.
 

Ed H

Member
Oct 18, 2012
167
Mine has done the same thing since I bought it. That little stumble with low voltage. I know it's not the throttle body because it is brand new. I just replaced the thermostat this weekend and therefore removed / re-seated the alternator connector. I will know in a couple days if that fixed the issue.
 
Dec 4, 2011
520
CaptainXL said:
Yeah, but I drove this truck a lot more in the past two winters and never notice it. I really think there is a problem.

Not to knock your winters but its usually the real cold days here -30C, maybe that has something to do with it, or perhaps it is the truck telling we BOTH should have stayed home. LOL
 

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
RedEnvoyDenali said:
Not to knock your winters but its usually the real cold days here -30C, maybe that has something to do with it, or perhaps it is the truck telling we BOTH should have stayed home. LOL

It's ok, I used to live in northern Ontario and North Dakota so I know what a real US winter is like. It was rainy and relatively warm today about 36F. I drove it the last couple weeks when it was 0F and it never did it. So not seeing the connection.
 

dfc739

Member
Jul 29, 2012
170
Des Moines, IA
My truck used to do this also. My alternator developed a bit of a squeak so I took it to a neighbor that rebuilds alternators and starters for several of the local shops. I figured a bearing was going bad in it and just needed to be swapped out. Instead, he said the commutator was doing the squeaking and the bearings were fine. I asked him to make it "like new" and $80 later I have my rebuilt alternator (which hasn't done the lights dim yet). He went ahead and put in new brushes, a voltage regulator, and a couple other small things. But the new commutator was the bulk of the expense at around $50. It was still cheaper than a $200 rebuilt from a parts store.

I need to state this though: I cannot prove this was a "cause and effect". But it seems like more than coincidence that my truck used to dim the lights for a few seconds while driving almost every time I drove it and in the two months since I put the junkyard and later my rebuilt alternator on it hasn't done it a single time. I didn't replace any other belt-driven accessories in that time.

While I had him rebuilding my alternator, I swapped in one I picked up from a junkyard so I could still use my vehicle. Do you have a buddy or a junkyard nearby you can try?
 

CaptainXL

Original poster
Member
Dec 4, 2011
2,445
dfc739 said:
While I had him rebuilding my alternator, I swapped in one I picked up from a junkyard so I could still use my vehicle. Do you have a buddy or a junkyard nearby you can try?

I would be doing a rebuild (just cause I like fixing stuff myself) rather than picking up a used one. Will just keep driving it and note if it does it again within say... a month. Failing that, I would be getting a new Delphi unit from a local retailer.

gmcman said:
Mine did that a few times and I wiggled the signal wire here (in pic) when it was acting up at it came back to life. Once I realized it may be the culprit I pulled the connector and sprayed some electronics cleaner in the connector and has been fine since.

Hmm, I will do that if it comes back. Will check continuity as well while wiggling the wires. But yes, it seems as if the field control signal from the PCM just disappeared like when performing a cold start of less than 32F.
 

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