My '97 Ram 1500 P/U isn't charging. The alternator checked out OK in two different shops. I'm told this alternator has an external regulator and it is "inside the computer."

So where is this computer, and what is it called? There's a "powertrain control module" on the firewall, but the carging system doesn't have anything to do with the powertrain, so am I looking elsewhere? Any diagnostic suggestions?

A voltmeter shows 13 v at the battery whether or not the engine is running. (I charged the battery with a shop charger.)

HELP!!

 

In the service manual it says the voltage regulator is inside the PCM. If the regulator is bad the PCM must be replaced.

 

ya, if the regulator is bad then the pcm will definitely need to be replaced, but that is usually not the cause of the alternator not charging. take that voltmeter and check the voltage at the alternator(should be a large terminal on it where you need to hook your positive lead up, and put the negative lead on the positive side of the battery) if your getting around 14 volts then your alternator is good. if thats the case then have a shop check out your regulator in your pcm, or if you wanted you could look up the wiring diagram and check it yourself, but pcm's are no joke, if you screw up its gone and you'll definitely have to replace it and they are not cheap mind you.

 

simple alternater test...start up truck, unhook bat if it keeps running alt is good

 

The output from the alt may be good and the fuseable link between it and the battery may be blown. If the above mentioned test fails, ohm check the wires through the link. (if someone hooked up jumper cable or a charger to the wrong posts, this can blow very quickly). Also, did they check the alt in or out of the vehicle? If in the vehicle, and the output of the alt is good, I don't think it’s the PCM.
Kurt