C. Solomon said:
My pickup does the same thing and it only happens in colder temps. I wouldn't make a big deal out of this at all. I think the reason the check gauges light comes on (just as it was stated before) is because of the grid heaters. Think about it, the split second your motor fires the grids kick on (below 63*) or something. So they will draw power just as the alt. starts to charge. It will take a few seconds for the alt. and batteries to catch up.
Even at 40* degrees your batteries are not at full cranking amps. The colder it is the weaker the charge on the battery. I don't care what you have for batteries cold temps will effect them.
So I wouln't go spending money or time on this problem.
If my pickup cranks over fast like it should I know my batteries and alt. are fine.
Yup, C. Solomon has it dead on.
The check engine light comes on when the grid cycles on and drags the voltage level down to a certain point. Once the grid cycles off, cause your engine/manifold is warming up, the volt meter will start to come back up as it charges the batteries.
Since the grid is on for a while in the cold, and yes even at 50degF, it's taking most of the current that would normally go to charing the batteries.
Once the engine warms up, and if it's 40deg or 50degs out, but not warmed up well, you will still having the heater grid cycle on, you can see your voltage guage drop and your headlights dim. Then when it cycles off the volt meter comes up even quicker , and the brightness of your lights comes up real quick too.
This is all real common operation once you get in the 50's and below.
At about 25degF, your battery is at about 1/2 capacity. It's a pretty linear line of capacity loss for all lead acid batteries from 75DegF to 25DegF, if I remember the charts right.
Plus at 50 or 40degs F it took more to crank your engine over... the oil does start to get thicker.
All these things are reasons why at 40DegF and lower, Dodge recommends you start plugging the truck in. It starts real fine, but life is much easier if the block and oil are a bit warmed up.