When it's cold outside and I first turn my truck on all my lights dim for a minute or so and then get bright again, and this continues for a while. When they dim I hear a clicking noise on the passenger side of the engine compartment. The stealership tells me this is normal, and the noise is a heater that heats the air going through the intake and the lights are dimming because the heater draws so many amps. Does this sound right?

 

The stealership is right. I have an 06 and it does the same thing. It will keep doing it until it is warmed up

 

Perfectly normal. It's your grid heaters cycling on and off. They draw a huge amount of current.

Nothing to worry about.

 

HMMWVs (Military hummers if you don't know the acronymn) do the same thing.

 

yeah lots of amps... look at that voltmeter swing too.

 

Wow. I have the same issue (I guess we all do.) I thought it had something to do with the alternator and battery, and maybe some cycling going on.

Thanks for the heads up.

 

Good 'ol military HMMWVs... Yep, I remember that now.

 

Cummins is in the Hummer too!

 

would that happen if ya had dual batteries??

 

There is two batteries. The heaters just draw up lots of amps.