i have a 98 24valve that has charging problem. after you start the truck, it takes a while before it will start to charge. be it cold or after driving a while.
it will charge then quit, then start again. this will go on for a while then it will start charging and work fine.
spent the big bucks and replaced the alt. still does the same thing. the batteries are good, cables clean etc.
i read somewhere that the crank sensor could have something to do with the charging circuit. this true or not.
the truck has 210,000 on it.

 

Does this happen only when you restart the truck? If so how cold is it where you're at? The reason I ask is because it could well be your grid heater giving you the impression your alt is not working properly.
mishkaya

 

this happens when ever you start the truck. hot or cold.
the pre heater did cross my mind but it does the same thing after you've driven it 20 miles, shut it off for 10 min. then restart it.
oh yea, it's 16 degrees here in kansas.
the pre heater shouldn't work after the the engine warms up, right?

 

Grid heater works any time the temps are below 40 F when you start your truck. I am very confident this is your problem, especially if it quits once you are over 20mph.
mishkaya

 

is the grid heater a dealer item ? could it be the controller for the heater or is it the heater it self?

 

I do think it is a dealer item, but there is nothing to worry about. It's perfectly normal for the truck to do this in cold weather as the grid heater sucks a tremendous amount of juice.
mishkaya

 

yes but, it's never acted like this before. had this truck for 5 years and it's never acted like this in the past. in the past it has pulled the batteries down as it cycled but, not like it's doing now. it pulls the voltage down past 10 volts and takes forever to recover. the batteries are good. 'bought burn't my load tester up running load test on the batteries.

 

Could be a problem with the grid heater then, there was a write-up on them here somewhere, but I'll be darned if I can find it now. Hopefully someone with more experience with them will chime in.
mishkaya

 

Try this http://dodgeram.org/tech/dsl/trouble...niford_htr.htm

 

nothing wrong with the grid heater. unhooked it and still have the same problem.

i'm going to change the crank sensor and put regular mopar voltage regulator on it.

with the block heater pluged in this thing starts like it's 80 degrees outside without the grid heater working.