My truck stopped charging about 2 weeks ago. noticed it on the way home one night (dim lights). next morn no start. charged my battery and went to work and put a meter on it ,sure enough no charge. got a new voltage reg from napa and it was charging again . a little high though about 15 volts. I let it go. by Saturday of that week (5 days) my battery blew up. Monday went back to work and checked it and was charging 18 volts. needless to say put in a new batt and voltage reg. still slightly over charging. fast forward to this sat and again over charging but caught it and unplugged the reg. back to square one. not that it couldn't be an issue but the alternator is about a year old.

Would probably help to give the year, make and model.

sorry to me there all the same. 89 pick up with a diesel. same voltage reg from 70 to like 92 or so. and it's in my sig

under charge or no charge, sure, bad reg.
2 showing over charge and I would start looking at the bulkhead connectors and checking sensing line voltage for a drop vs battery, or grounds to the vr.

yep i'll check the wiring it was all good before the first reg went bad. after the second reg went in if you brought up the rpms it would charge in the 14.7 range which is where it should charge. the ground is good, first thing I always check on any mopar voltage reg.

Actually, not all the same. In 89 the gas trucks used the computer to control the charging, dunno about the diesels though. So the information is important.

If you have had two bad VR's then I'd look elsewhere.

Yeah my Diesel has just a basic mopar electronic voltage reg. All of them now made in china.

Yeah those regulators are terrible.

#1 confirm that you have a good (not sulphated) battery in there (that is capable of being charged), that is fully charged. If it is that new one you should be good there (& likely fully charged if not over that by now!).

I would be checking my grounds and voltage feedback to the regulator.

I had the same problem wound up being the wire between the alternator and the voltage regulator having a really high resistance. Tim

Exactly my point!

The timing of this thread is perfect. My B-van has been doing the same overcharging BS for awhile and it would come and go. This weekend I finally tore into it and after lots of metering and parts swapping nothing changed. (And YES that stupid VR was thoroughly grounded) As my last resort I made a test cable to bypass all the factory crap and lo and behold it starting charging perfectly @ 13.7 volts. plug in the original crap and its all over the place again. Measuring the key on power at the alternator and voltage regulator it was barely 11 volts just sitting there with the key on and not running. There was enough voltage drop through coming off the battery, through the bulkhead, ignition switch, back through the bulkhead and off to the rest of key-on 12volt power that the VR and alternator field could not get a clean consistent 12-13 volts so it was ramping up the voltage compensating thinking it was necessary.

Awhile ago I rewired the A/C clutch circuit to use the original power wire as the trigger for a relay because coming to idle the voltage drop was just enough that the A/C clutch would cut in and out. I'll probably do the same thing for the key-on 12 volt power circuit. Even with clean and greased connections theres just enough voltage drop in some cases to cause all sorts of gremlins that come and go.

I have '91 diesel that had the same problem. I replaced the voltage regulator at least five times before the battery gave up. I checked all the grounds and even ran a separate ground from the regulator case to the battery. Still overcharging, so I replaced the alternator, made no difference.

There is a guy on the Turbo Diesel Register (TDR)website who has adjustable regulators for sale that he had made. I spoke to him on the phone and he told me how to test my charging system. I was not able to locate the cause but I bought one of his regulators, adjusted the voltage and haven't had a problem since. That was about two years ago.

His screen name over there is Mysteryman. You might want to check out some of his posts on TDR.

Adjustable voltage regulator

http://store.alternatorparts.com/partnoc8313.aspx