does anyone have any idea why my lights flicker, all my light inside and out


Asked by Nov 26, 2012 at 05:37 PM about the 2008 Dodge Ram 2500 Laramie Quad Cab 4WD

Question type: Maintenance & Repair

my lights flicker when on inside and out my dash,head lights interior everything

22 Answers


what engine is it equipped with. and does it do it all the time or just when you start it in the morning or after its sat for a long time?

15 out of 15 people think this is helpful.

Diodes in the alternator are going, this is most noticable at idle. Check for bad connectons at battery , alternator and grounds.

17 out of 17 people think this is helpful.

Not necessarily Chrysler charging systems are highly based off of battery temperature. This truck has battery temperature sensors in the battery tray, dodge trucks cycle the PCM controlled voltage regulator on and off at a set voltage of 12.8 volts until the batteries reach a specified temperature, this will cause dash, over head, and head lights to pulsate.

14 out of 14 people think this is helpful.

It does it once the lights get turned on and has gotten worse sometimes more then others, its like i have huge amp in there. lol, I have had people pull over thinking I was a cop behind them. not sure if I need to take it to dodge or I can fix it just need some guidance

22 out of 22 people think this is helpful.

Dan it has the cummings

6 out of 6 people think this is helpful.

Does it happen all the time, or when the truck is cold like has sat over night, or for a number of hours?

11 out of 11 people think this is helpful.

My '03 Cummins equipped truck does the same thing when the grid heater kicks on and off. I can watch the lights in the truck dim and my headlights will slightly dim and then come back on. Only notice this when it's cold enough for the grid heater to come into play.

4 out of 4 people think this is helpful.

Thats just because the heater draws alot of current. Similar things happen when ac kicks on or things like that.

2 out of 2 people think this is helpful.

The grids only make the lights flicker because on a cold start the BCM is reading battery temp, and only charging at a 12.5 volts just enough to keep from damaging ECM contained injector drivers. chrysler picked a shitty way to build their charging system which is why I run a GM style 1 wire alternator on my 05 Cummins.

4 out of 4 people think this is helpful.

I was stating this fact as a possible solution to the OP, not looking for an answer to a problem. Maybe this is what he is noticing.

2 out of 2 people think this is helpful.

Yeah thats what I was gonna tell him if he replied to my question that I asked like 4 posts up about ambient temperature, my guess is he figured it out himself haha


it is just the grid heaters turning on and off, no problem normal operation

1 out of 1 people think this is helpful.

It is not the grid heater, listen to the symptoms. He didn't say dimmed down, he said pulse like cop headlights. I have had many Dodge trucks, and now my '07 is having this pulsing problem. Instead of guessing, it would be nice if someone who really has had this happen and had it fixed would reply.

9 out of 9 people think this is helpful.

Sorry, let me just miracle it fixed. I dont even know why I continue to put information out on this any way. its absolutely useless talking to what 90% of the time are knowledgeless people. If you want your truck fixed, drive to Conway, South Carolina, and I will gladly fix it for you instead of just give away good information and starting points that youre going to ignore any way. but I just want to know, if youre so sure that its not the grid heater, why your problem fixed?

7 out of 7 people think this is helpful.

my 08 dodge with cummins does the same. interior and exterior lights dim and brighten & the engine lopes at an idle. I turn the blower motor fan on high it stops and everthing is normal. I come out in the morning and sometimes I need to jump start it and sometimes I dont. I dont know if it is a battery or the alternator. It doesnt do it all the time but more frequently in the last couple weeks now.

5 out of 5 people think this is helpful.

I have the same issue with my '08 Cummins. The interior and headlights pulse. They will do that for a while and then they will quit, only to start again later. At first I noticed it more when it was cold, but now I have seen it do this at 60 or 70 degrees. I took it to the dealer 2x and each time I was told it was a known problem and the turbo pre-heater draws so much current it causes the lights to pulse, I don't know if that is accurate or not, but sometimes people pull over and get out of my way. I guess they figure it is a police truck behind them.

2 out of 2 people think this is helpful.

I know exactly what he is talking about. It has nothing to do with the truck being a diesel. My 1993 Dodge W-150 which is gas does the same thing. My head lights and dash lights flash off and on. I have replaced the light switch and the plug in the switch plugs into. Still haven't found the solution.

1 out of 1 people think this is helpful.

All warning..idiot lights flicker on and off

2 out of 2 people think this is helpful.

I went through an alternator and that didn't help. Found out it was one of my batteries!!! Stopped flickering when I replaced my bad battery. Guess the alternator was wigging out and spasms when one battery goes out.

3 out of 3 people think this is helpful.

Thank You all...Glad to know I am not alone. Just scary to be driving at night and my headlights go off...I called dealership where I bought truck and the service dept said they never heard of this and since I am out of warranty would charge me 95 dollars to look at it. I am going to cancel appt ...Doesn't seem like anyone has had luck fixing. Truck is a 2013 bought new. Now has 23k on it. Just started doing it a lot recently...frustrated.

I had this exact problem on my 04 Mitsubishi eclipse. One of the only aftermarket parts was a pep boys alternator. Everything tested fine, battery was fine, grounds everything. No one could figure it out. But I noticed that the lights flickered more when I gave it gas. So I put a meter on it, and as always it showed the proper voltage when idling etc. Then I watch the meter while I reved the engine and it went all the way up to 15.4 V So it was a bad voltage regulator. Pep Boys replaced the alternator under warranty and the problem was fixed.

FYI - max voltage should be no more than about 14.4 V and should idle around 13.4 - 13.8 V

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