Engine/Transmission (1998.5 - 2002) alternator problem

[MDSlover]

started truck up this morning alternator was charging right at 14 volts like it always does then slowly goes to discharge check gauge light comes on turn truck off re start now its charging again any ideas on what to look for

 

[rjrkihap]

You probably already know this, but just in case... The grid heaters will cycle causing the gauge to go up and down (lights will dim a bit when it cycles on). If it's cold enough my check gauge will come on also. It usually shuts off within a few seconds.

Good luck.

Ron

 

[FourBarR]

You didnt mention how cold it is where you are. Its 28 deg. here. I have 523,000kms (321,000k ) Mine has always worked as follows: Key on ,wait for start light to go out ,start engine charge rate slowly goes up to 14 + volts and stays there. In weather where temperature goes below +20 F. there is a slight decrease in voltage as grid heaters cycle.

 

[24V-DSL]

Have you checked for codes?

 

[MDSlover]

no codes first time it has ever went all the way to the left and stayed there it is 50 degrees here it was like the guage was not hooked up then turn key off restart and now its charging i hate not knowing when its gonna screw up again

 

[Skydiver]

As a process of elimination, next time the alt guage stays down for more than 20 seconds after it is running pull one (doesn't matter which) of the small control wires off each grid heater solenoid. Could be sticking grid solenoid(s). You could try lightly tapping them.
If you wait till the gen light comes on just shut it down and restart it. My last sentence is from 12 valve knowledge. When my grid relays stick in the energized position the ecu will disable the charging system from the overload.

 

[MDSlover]

its funny you said something about ecm ever since my truck had its meltdown ecm lift pump vp 44 lots of wiring and injectors the truck had to be sent to cummins to be reflashed and its never been the same it idles different the lights dont dim like they used to and overall just doesnt perform like it did i even changfd the superchip flashpak back to edge i thougt that bigger injectors and all the new parts would make it run way better and now having this new problem makes me wonder if its all worth it

 

[Skydiver]

With that many different issues I would say "check all the grounds". Disconnect both positive battery leads, take a volt meter and see if you have less than 0. 3 ohms resistance from the ground wire(s) to where it connects to the engine or body. A VOM tells you how your grounds are actually conducting.
Are you near road salt?

 

[VHolloway]

they needed to put 200 amp are bigger alternators on these trucks from the factory

if i keep my truck i'm going with the biggest one i can find.

a little overkill never herts