I had the check gauges lamp come on and noticed low volts the other morning, it climbed back up after a few seconds and the check gauges lamp went off but the voltage was only at about 11-12v range on the gauge (usually 13-14).  I took the alternator to autozone, bench tested showed bad, got a replacement and bench tested before leaving, that one tested good.  Also tested batteries, both good.  I installed everything and still nothing for charge voltage though. 

After reading some other sites about the PCM voltage regulator going bad, I got an external voltage regulator and was about to connect it up today, but I read a post here a couple of days ago and it got me thinking about the connector/cable and testing that first. 

I pulled the little 2 wire connector from the alternator, started the truck and tested from the alt plug using a test lamp between the blue wire and neg- post and get light, but when I tested between the green wire and pos+ post I only get a dim light. 

The next thing it says to check if everything is good is the cables from the alt to the PCM but I don't know if the dim light for the green wire is good or bad...  I'm about to check that out now, just wondering, do you have to remove the neg battery posts before removing the PCM connectors for that resistance check on those cables, or just keep the key turned off and pull the connectors off with the batteries connected? 

 

Key off and battery disconnected per Dodge factory service manual.  With out disconnecting the battery a large voltage spike could surge through the PCM when unplugging/plugging the connectors to it. 

That wasn't mentioned in the write up but I thought that would be the thing to do.  Cables were good between the alt and PCM so I assume the PCM is bad and threw on an external voltage regulator and now it's at least charging again!  It's ~14.7 which is kind of high I think but the operating range so far (according to edge monitor) is 14.3-14.9 from what I am seeing on the edge gauge and regular gauge, voltmeter to batteries match at idle ~14.7.  The problem now is it's throwing these codes: P1693, P1594, P0622.   I thought these were here from before the regulator change out so I cleared them and turned off the truck, then started up and took it for another test derive, they came back on when I got home.  I'm seeing this is common for these external regulators on my year truck to do that, but that's another days battle, at least it will get me to work until I decide to make that permanent or not. 

On 2/24/2018 at 4:39 PM, 53Block said:

I only get a dim light. 

 

Normal that is how it regulates power from the alternator by controlling the gorund leg and vary ground voltage amount. 

 

I'm going to bet your Alternator fuse is blown or cracked. Remove the two 8mm bolts in the fuse and test it with a ohm meter.

Thanks, I should have checked actual voltage on that lead when I did that test, maybe I'll do it again and play with the rpms and AC to see if it changes at all.  But I don't think it's blown since I got matching battery voltage at the alternator + post, I guess it's possible it could be cracked or making just enough of a connection to match the voltage but not the amps.  Either way I'll try the ohm test with it off the truck and see, I just ordered 2 fuses today so if that is the issue I can replace it and have a spare, hopefully that's all it is. 

 

There isn't much to the alternator system. 

 

Blue wire should have +12V with the key on. 

Green wire will vary ground signal to control charging rate. 

Then a fuse for the alternator. 

 

 

Is this an updated one for the 99?  The one I have doesn't show the bat sensor (but I definitely have one).  Once all my parts come in I'll test everything out and report back. 

Should work for all 98.5 to 2002 trucks. 

 

A little history if you didn't know. Dodge, Plymouth and Chrysler all use the very same regulator wire colors for many many years dating back from the 60's form what I've seen. Blue was always keyed hot and the green only came from the regulator as a variable ground. The only thing that changed was external regulator was moved into the PCM and given a battery temp sensor to monitor battery temperature and prevent boil out like the old regulators were known for. 

 

So today's charging system on our 2nd Gen truck the design dates back to the 60's. 

Thanks Mike, now if only they would charge the 60's or even 90's prices for all these parts I need for my truck, haha.  Well, I finally threw some wrenches at my truck this weekend, replaced the battery temp sensor, replaced the alt fuse (ohms were .001 out of truck on original fuse but replaced it anyway), cleaned up and reconnected all my main grounds (bat to block to frame to body) and the pos post connections including in the fuse box, reset all fuses and relays while in there, cleaned off bat posts, sprayed contact cleaner on the C1-C3 PCM connectors, double checked the ohms on the original blue and green wires from alt back to the Cx connectors (both showed .002), hooked everything back up and.... still no charging from internal regulator/PCM...  So I rerouted the external voltage regulator wires and relay for a more permanent setup, threw some wire loom in there and connected that back up, it's back to charging on the external regulator, so I'm just assuming the internal regulator in the PCM is toast.  It does charge at about 14.6 (between 14.3-14.7 on edge) so I'm curious to see if the warmer weather will make that change at all or if it's always fixed at that number, but I'll have to keep an eye on it because I don't plan on a new PCM just for the alt to get a charge to the batteries, unless I start having other electrical issues down the line.