RAM2940

Ive been working on a 1990 d250 cummins 4x4, cannot get the charging system to work correctly. It has a new altanator, voltage regulator and battery. Put voltage reg on started truck and blew the volt. reg. Found that we did not have a ground. Bought another volt. reg. ran a ground from alt to volt reg case and one to the frame. Started truck, charging system started working at idle. It idled for about ten minutes with 14.4vdc charging. Revved engine to about 1500 rpm and then it stopped charging and blew the volt. reg again. Bought another volt. reg. Then we decided to remove the field terms off the alt and ran wires to the volt reg and cut the connector off the volt. reg and connected the wires from the alt to the volt. reg connector and tapped into another 12vdc line. Now the charging system bounces continuously fron 13-15vdc while idling or revving the motor. Used dvm to test. Can someone tell me why the alt is bouncing the voltages. Need help.

RAM2940

Any suggestions or ideas.

eng208

Are you sure this is the right alternator? These are externally excited alternators and if you have an alternator with a built in alternator or internally excited fields, it could cause what you are describing. Also, make sure you have it hooked up right on the terminals.
Chris

Sootblower

I have the 91 and I have noticed my dome light has always flickered in brightness at idle. I think it was normal for the 1st GEN and you have fixed it. I blew regulators when ever my ground at the regulator got rusty as well. Common problem. I think 2nd Gen has regulator in the engine computer. Costlty when it goes but I think it has better voltage regulation.

RAM2940

I definetly has a voltage swing of about 2vdc 13 to 15 at the battery. When the headlights are on they flicker at idle and when revving the motor(looks like strobe). Also volt meter in dash is bouncing. I am going to disconnect the voltage reg connector and test alternator to see if it puts out constant power. We had it tested at advance on tester and it put out constant volts.

Sootblower

Tell us what you found. By the way, petroleum jelly on the rubber connector and ground bolt holds back corrosion. Rain water runs down hood and directly on regulator when hood is initially opened. I also have to be careful not to open hood after a hard mountain climb since very exhaust manifold is prone to cracking when water hits.

RAM2940

When all these problems started, something burnt up, smelt smoke in cab. We finally found one of the heater grid relays(guessing one of the two black modules behind the battery) had shorted and caused a constant drain on the battery. disconnected that and system is charging. Charges normal at idle but when motor runs faster than idle we still have the bouncing voltages. At least it is now drivable. But still going to continueto troubleshoot. Thinking about trying another voltage reg.