When I start my truck in the morning, the voltage will vary with RPMs. For instance, it will read 14volts, then drop a little bit, RPMs will drop a little, lights will dim with the droping. I am not running headlights, but I am running a stereo. Could my alternator being going bad from the power draw. It only happens in the morning. Then it returns to normal, then happens again in a second. Any thoughts fellas?

 

It's your grid heaters cycling off and on.
Totally normal when the temp drops below 50°

 

I have been noticing the exact same thing. When I start my truck in the morning and revving it at 1000 rpm to warm up for a minute or so, the voltage will go right up then drop, then climb up, then drop. Its really weird, It wont affect my stereo at all will it, I dont really wanna screw up my nice new head unit

 

It wont hurt a thing. Its thegrid heaters cycling, and its made to do that. Its completley fine .

Eric

 

Wuld upgrading to a bigger alternator help with the voltage drop? I mean, having an alternator with more idle output would seem to keep any voltage from dropping. Especially with lots of lights, stereo, and grid heaters.

 

The grid heaters on a 12 valve stay on for a maximum of 3 minutes or until you hit 17 mph. Just wait to turn on your stereo until they finish cycling or you're on the road.