tbran
Guest
First check the cab ground. Then to check and see if it is the relay, take the relay out of the system by connecting BOTH big wires to the same BIG post on one side. This fools the system to thinking it has a perfect relay. If everything is now OK you have a bad relay. IF not then have the alt checked as it is overcharging IF it is really putting out 16V and drops to 13 It should only drop1.5 - 2V unless your alt has been replaced with a lower amp unit than came on it or the belt is slipping. Finally check the wires out via the op man wiring system and make sure you did not get somthing in wrong.