We are having a problem with our headlights on our 01 turbo diesel ram truck. They seem to be pulsating. The power being sent to them seems to be inconsistant which causes them to dim and then return to normal brightness. Please help if you have experienced this.

 

It could be your grid heaters coming on and off if it's cold enough (below 50°) this is normal.
Does it stop once the truck is warmed up?
Is your voltmeter dipping it time with the lights?

 

batteries good?

 

Additional info: The gauge does not move as the lights dim. This is happening when the truck is warmed up. It has often done this thing as it is warming up but now it is happening well after that. It has not been below 50 here.

 

You may be losing the regulator in the PCM. I lost mine as a few on here have. If this is the case it is easy to wire up a separate regulator.

 

My '01 V-10 lights would dim very briefly when the A/C clutch engaged. Likewise with my '92 Spirit. Does the pulsating happen when the A/C or the Defroster is on, or all the time?

 

It was happening all the time. We found a loose connection. Sometimes those are the toughest to figure out. Thanks to all those who offered suggestions.