well tonight i went n helped a buddy put a new alternator on his truck. his batteries were dead so we hooked up the cables to my truck, left it sit a couple minutes, then fired his truck up. when i went to leave, i noticed all my interior lights are extremely bright, my voltage gauge is buried all the way to the right on 18. i wiggled the connection to the pcm, then the lights got dim, voltage gauge dropped to 12, and the tach stopped workin. drive down the road a little n back up to 18+ volts. im tired of dealin with this PCM crap. anybody have the schematic for wiring up an external voltage regulator? n what regulator do i need? is my tach still gonna work?

 

External Voltage Regulator Install With Pics - Dodge Cummins Diesel Forum

 

thank you

 

i have the same problem with mine but when i first start it and its cold it jumps from like 9v to 14v i thought it was my alternator because i just put new batteries in it because the old ones went dead do u think i need a new alternator or should i put a voltage regulator on it too

 

well i went n got a 4 post regulator, hooked it up exactly as every diagram i could find said. fired up the truck, voltage gauge reads about 15, but the regulator started smokin... is it possible for the alternator to go bad n out out too much voltage? just wonderin before i go pull it off n drive 40 miles to have it tested.

i hooked the field post on the reg to the top small nut on the alternator. the other small nut i hooked to ground. i hooked the big wire back up to the bottom post on the alternator for the positive to the battery. i hooked the ground on the alternator back to ground. i left the second post on the reg open. the third i hooked to the positive on the battery, n the 4th to ignition. anybody have any clue whats up cuz i really dont know.

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well im takin the alternator to be tested, as well as replacing one of my batteries. i think the cold got to it, the sides are bulged n there is corrosion on the top of the battery. hopefully between the two of them somethin will fix it... if not, im settin it on fire......

 

yeah an alternator can go bad and send too much through the system, i worked on a machine once that this was happening, caused the battery to explode! normaly if the sides are bulging means it has been overcharged

 

had the alternator tested, it had an open diode so i bought a new one, also replaced the battery. hooked it all up n fired it up, it reads a little over 14 volts. but my external voltage regulator starts smoking. none of the wires get hot, just the regulator itself, should it not be screwed fast to the firewall that its grounded? i think im gonna try hookin the original reg in the pcm back up n see what happens. I HATE ELECTRICITY

 

haha yeah hook it up the right way and see, good luck!

 

i hooked it back up thru the original voltage regulator. start truck, 17 volts...
re hook up external regulator, but remove it from the firewall n isolate it, 17 volts. i honestly dont know what to do. the charging system wins, i give up

 

check your battery temp sensor its under the driverside battery if it reads wrong it will tell the pcm to open the voltage regulator up and overcharge