Edit: truck is the '01 3500 listed in my sig.

I was on my way home a couple days ago about 10 minutes into my roughly hour commute and the "check guages" light comes on and my volt gauge was all the way over to "8" like the key was off. The truck was running fine so I said the heck with it I'll worry about it when I get home. I didn't want to shut it off and it not start for some reason and have to trailer it.

Got home, shut it off and started it and the gauge came back up to around 12but wasn't charging which told me it was either the regulator in the PCM or the alternator itself, more testing and it was looking like the alternator so I pulled it and went to advance because I needed a sepentine belt anyway. They tested it and said it was bad, not having any luck with advance's electrical parts I dropped it off at the local alt/starter shop and he also said it was bad and said he'd have it fixed the next day.

So I stopped yesterday and picked it up, came home and put it on and all was good. I let the truck idle for about 20 minutes with all the accesories on and all voltages were good.

Fast forward to this morning and about a half hour into my commute the check "guages light" came on and the volt gauge went over to "8" and the lights got dim as in not charging dim, not short dim, I was looking for a spot to pull over and check connections and all, when they brightened back up like it was charging again, but the gauge still read zero.

As I was driving I clicked the key off and on real quick to reset the gauge and it came back up, and like I thought it was charging and it worked fine the rest of the way to work.

When I got to work I was checking connections and when I wiggled the voltage regulator wires on the alternator it quit charging, then I pulled them off and noticed there was dielectric grease on them from who knows when so I cleaned them then put some of the excess grease on the pins (there was none left on the pins) and plugged it in and it started charging.

My question is what causes the gauge to go to "8", my thoughts are is the wires were making bad connection telling the pcm something was wrong then it trips the gauge to set off the chime and "check guages" light, does that sound possible? My thoughts are to get some more dielectric grease and hope that solves the problem, if not it looks like I'll be getting an external regualtor.

I had the batteries disconnected when I changed the alternator so the battery connections are good, and I also checked both the grounds that go to the block too, so I don't think it's a grounding issue.

Any thoughts or experience is appriciated, I hate electrical gremlins!

 

try disconecting grid heater,had one did the same thing ,grid heater contol faiure

 

So the grid heater is turning on when it doesn't need to, is the grid heater controlled by the pcm? When it's cold I notice the grid heater cycles, especially when it's dark and the lights dim, but it's never done that out of the ordinary when the truck is up to temp.

 

I would favor the intake air temp sensor causing the problem with the grids.
Good info> http://dodgeram.org/tech/dsl/trouble...niford_htr.htm

 

Loose connections on the grid heater relays will also cause a similar problem. Locate the relays and remove and clean/crimp slightly the connectors for the grid heaters. The system ground through these relays and any loose connections causes them to cycle.

Having the alternator cut out should not drop your voltage so low.

 

Maybe I should clarify, when the gauge drops to "8" it isn't actualy down to 8 volts, it's just reading that on the gauge and the batteries have taken over and it's around 12 volts but the alt is not charging. Even if the alternator does start charging again and I go up to 13.8 volts the gauge reads "8" till I shut off the truck and restart.

 

Do you have a real voltage gauge, or is it just the one on the dash? The one on the dash isn't very accurate, and is slow to respond. Below the normal line is usually in the 10.8V area. Right on the 14 line is around 13.3-13.4V, true 14V will push the needle past the 14 in the gauge. Even with a bad alternator, the voltage gauge should still read in the normal range on batteries alone, assuming your batteries are in good condition.

The grid heaters will pull the voltage down into the 11.9V range typically with the engine running. I've seen about 11.2V with the engine off and the grids on.

I say get a multi-meter, when this occurs again, pull over, and start checking your battery voltage, and see if there is voltage at the grid heaters. Should be zero there.

 

Yea all my readings were from my muiltimeter.

 

I think I may have found the culprit, it did it a couple times on the way home today but it was intermitent so when I got home today I hooked the multimeter up to it again and when I touched the regulator wires on the back of the alternator the voltage started jumpimg. It turns out the plug was bad so I did a little surgery and got it working until I can actually get another plug which I would guess I'll only be able to find at a junk yard but either way at least I think I killed my gremlin!

 

Right on.. Good diagnosis.