After I start my 2003 Ram with the Cummins the dash lights, heater fan, and headlights if on, all dim for a few seconds then come back up then dim again several times. I can hear something around the firewall click on and off when this happens. I have only owned this truck a few months and not sure if this is normal. I thought it may be only when it is cold but I have noticed it after it is at running tempature.

2003 Dodge 2500 SLT Cummins

 

Ok dude I have a 02 2500 diesel and mine has done that since the day I bought it. I think it has something to do with the engine warming up but I am not sure. Mine really doesnt really do it after it warms up. I am a diesel mechanic for a living and I build engines all the time. I personally dont think it is anything to worry about. If you are worried though just stop by a dealership and ask them. P.S. I guess it could possibly be the alternator kicking in and out.....MAYBE. Just a thought.

 

Headlights alternately brighten and dim after truck is started
Normal, caused by high current draw of intake manifold heaters when temperature is below 60° F. If the problem continues at speeds above 18 mph, check for loose terminals on the manifold heater relays.

Voltmeter jumps up and down - Caused by intake manifold heaters cycling when engine temp is below 60 degrees.

Lights flickering 1998-2002 diesel
1.Lights will normally brighten and dim at idle as intake heater grid cycles on/off
poor connection on the intake air temperature sensor connector - clean pins and reassemble
2.Charge cycle unstable - replace PCM
3.Bad intake manifold heater solenoids - replace
4.Loose wires on intake manifold heaters - tighten connections

 

Thanks for all the info, sounds to be normal. Thanks again,,, Great Forum