So when I go to turn on my truck whether warm or cold the voltage cycles between high 10 low 11 to 14. I figured it was the grid heater but even if the wait to start light is on for a quick second it does it the same as if it were on for an extended period of time like a start in the morning at 10 degrees not plugged in. Load tests batteries, both good even though they are showing age at almost 3 years old and being cheap Murdock batteries that came with the truck and I just put in a reman alternator because it tested low amps and bad diodes. Its kind of a pain at night having to sit idling for 5 minutes so the lights don't keep dimming and going bright going down the road. It only does it on start up and bumping up the idle to 1100 to 1200 actually seems to make it worse. Once its done with it at start up it doesn't do it idling or driving. I figure maybe the batteries may be testing good but they just aren't up to handle the voltage and amperage anymore? By cheapo batteries I mean they are 70 collars a piece new with only 730cca

 

The grid heater does cycle after the engine is running, and does pull a decent amount of current. I don't know for sure at what temperature they cycle at, but I'm betting this is what you are experiencing.

 

Mine did that tonight with 2 brand new batts with 1000 CCA each. 2X on the grid heater

 

i think normal in cold weather

 

ya mine does it too. I idle for a few mins. and then try driving away and it will start cycling again...

 

It is normal under 55 degrees I believe and you hit 18 mph it turns the grid heater off....found this in the owners manual a couple years ago when the same problem scared me LOL.

 

Hmm alright I figured the grid was pulling alot but I guess maybe I didn't notice it as much last year and it seemed like it dropped a lot.

 

Same here. It's normal.

 

It seems like it does it more in the 98.5-99 trucks had a 99 too and it seemed to draw down worse than my 01