erratic charging problem

[OnVacation]

I'm having a charging issue. Truck lost all power on the way to work this morning. Popped the hood, and realized the charging cable from the alternator to the battery was broken (I'm guessing from when they pulled the cab off the truck...). Replaced the cable, got a jump, and she was running fine. tapped the pedal, the voltmeter jumped up a little. I left to let it idle for a while. Came back 10 or 15 minutes later, and no gauges, no power at all. Jumped again, thinking maybe idle wasn't high enough to charge a totally dead battery. Truck seemed to charge fine on the drive home by the voltmeter. Got home, and then watched as the voltmeter dropped to zero when I let off the gas. I gave it a little extra pedal, and the gauges went erratic, so I shut her down.

I checked connections on my voltage regulator, and all connections were good. So, I pulled the batteries and replaced with a known good battery.

Truck started fine, but was slowly draining voltage when I turned on any accessories. I tried giving it a little pedal, and again the gauges jumped like I was cutting and applying power (only did it at relatively high RPMs, maybe 2700+). I cut power and came in searching for advice. I can pull the alternator and have it load tested in town. Could this be a voltage regulator problem? Any other ideas?

 

[L6powered]

Check the crank speed sensor. I had the same issues with mine. It will also shot-off the AC compressor and kick out overdrive if it's an auto.

 

[OnVacation]

checked the speed sensor. its gapped to about .047", which is a little tighter than spec.

But, the wire for the speed sensor doesn't go anywhere...

keep in mind, this 12V is in a ford. So, I got a few pictures of the numbers on the alternator, which didn't turn out very well. but, I pieced them together as best I could. the sticker reads:

5602 7221
TN121000-4150 12V
FAMILY 120HS
DENSO


There is some smaller writing at the bottom of the sticker that is unclear. I'm not sure if the alt. is a ford or dodge piece. I do know that the alt. is hooked up to a motorcraft voltage regulator, so my guess would be ford...

I can try running the truck into town tomorrow and have an on-vehicle test ran on the alternator and check output. I'd prefer to avoid removing it until I know the alternator is the culprit.

Anything else to check?

 

[OnVacation]

okay, did some more searching. Apparently the alternator number cross references to a 93-94 cummins. and I found some information regarding using a ford voltage regulator to bypass the factory PCM. So, I'm not sure why the engine speed sensor is still hooked up since it's not going to anything.

Since the engine isn't ever actually charging the battery, just slowing the rate at which the battery drains, I'm assuming that this is a case of a bad alternator.

Since I'm sick of tracing down bad wiring (PO did a good job overall, his wiring wasn't the greatest...), does anyone make a good 1-wire alternator for a 2nd gen cummins?

 

[stubz616]

okay, did some more searching. Apparently the alternator number cross references to a 93-94 cummins. and I found some information regarding using a ford voltage regulator to bypass the factory PCM. So, I'm not sure why the engine speed sensor is still hooked up since it's not going to anything.

Since the engine isn't ever actually charging the battery, just slowing the rate at which the battery drains, I'm assuming that this is a case of a bad alternator.

Since I'm sick of tracing down bad wiring (PO did a good job overall, his wiring wasn't the greatest...), does anyone make a good 1-wire alternator for a 2nd gen cummins?

you can use a cummins alternator with the ford voltage regulator. the regulator should be a three terminal one. one wire goes to key power, one goes straight to your battery, and the third one goes to one of the little posts on the back of the cummins alternator (those are your field posts that control the charging rate of the alternator and it doesn't matter which one you hook that wire to) and the other little post on the alternator (whatever one you didn't use) just gets grounded to the case of the alternator.