Ok I have been pulling my hair out here and this is what I have so far...99.5 7.3, I have put a new GPR-110, and my truck still fails to start in the morning. (about 45d) I just did this check and here are my numbers. On the GPR, I had 13 volts on the passenger side post(large) 0 on opposite with the key off.
With the key in the on position I had 10.3V on the drivers side post(large), when the wait to start light goes outafter about 6-8 seconds, voltage rised to 10.9V. After 3 cycles truck started.
The voltage went up to 11.6V and rises with throttle, to about 12.6V.after about 30 seconds to a minute, voltage dropped to 0 volts.
I then shut off the truck and tried again. After 6 cycles truck failed to start and not enough battery to crank over. (duals)
Don't know where to go from here, cept dealer and that is last resort only.