My 99 Cummins keeps dying. Almost overnight anymore its annoying having to jump my truck in 20 deg weather. When I first get in and it actually starts my volt gauge will go up to 14 and I can hear something turn on and all my lights dim the volt gauge drops back down to about 10 and repeat (for like 15 minuses) I took the truck to a local shop ( stupid idea I should of tried to find the problem myself) my question is what's killing my truck?? Is got a brand new maybe month old alternator and 2 red top optimas also almost brand new. And I'm afraid whatever is causing all this is going to kill my new batteries or alternator any ideas what it might be??

 

When its cold outside and your trucks volt gauge is up and down, lights may dim a little after you start it; the grid heaters are cycling to warm up the IAT, this is normal.

Get a multimeter and start testing the batteries when truck is off. Also check all electrical connections especially your grounds.

 

Do you know what temp it stops cycling because It was about 170 the other day I was in mc ds drive thru and the lights weren't dimming as much but I could hear my blower motor bogging down when the grid heater or whatever it was kicked on