I have a 99 3500 single cab 2WD 5.9L that dies every time I switch the headlights on or turn the heater fan switch on. The truck does have a snow plow on it. I was at the gas station, came out turned the lights on and it died after a night of plowing. I have done as much trouble shooting as I can (check the grounds, checked for any loose wiring, ect...) I am not sure what to check next and out of trouble shooting ideas. Any help would be greatly appreciated.

 

Is it a diesel? Asking cause you posted in the diesel section and I didn't know if a 5.9 came in a diesel version.

 

Yes it is a diesel 5.9L 24V inline 6.

 

Not much of a Dodge guy are ya? The cummins was a 5.9 from 1989 until the end of 2006.







Is it ANY electrical load that kills it? I'm taking a wild stab but I would take a close look at your relays. My guess is that something is either over-loading a relay and causing it to shut down, or it's grounding out or applying power to a wire where it shouldn't.

Automatic shutdown relay
fuel pump relay

But really there are a lot of different things it could be. Unplug the plow electronics and see if that makes a difference. If it does, there's an issue with the wiring, the electronics, or it's simply overloading whatever circuit it's tapped onto.

Is it shutting off the cluster, or is the engine just dying? Does it sound like it's just running out of fuel or like the key is being turned off.

 

Learn something new every day bud. Sorry to disappoint you. I see 5.9, I automatically think gasser. Thanks for helping him out.