Electrical short?

[Marcus2000monster]

One other thing. When idling this morning I would idle it up to 1200 rpm and when doing so the lights would dim a little bit including headlights and interior lights. Normal or no?

[Mopar1973Man]

Normal. The grid heaters draw 95 Amps for single element and 190 for both elements. So every time the grid heater cycle on for post heat it will pull the alternator down hard. I typically attempt to either set high idle to help keep the RPM up so the truck can warm up without straining the alternator or start and get rolling quickly because after 20 MPH the grid heater are disabled. This goes back to what kills the alternator diodes and creates the AC noise issue because the alternator isn't turning fast enough to cool the diodes so the overheat quickly and fail. Another reason some of us unhook the grid heaters in the spring of the year.