I've been driving this truck exclusively with a cab over camper since new about 26,000 miles.

One thing I have been noticing is that my camper batteries tend to overcharge from the charge line to the truck. My voltage meter has measured max voltage of around 14.8 to 15.1 volts (cold weather). Is this voltage within spec? The starting batteries seem to still be strong (they get topped off from the camper's solar panels).

Is there any way to adjust the voltage down to say 14.4 volts? Does this require a computer flash? Thx

 

The truck batteries are charging at the proper level in cold weather, mine regularly sits at 15+ volts when its very cold out. You could get a regulator to drop the voltage.

 

i would have the batteries tested individually. if one is low, then the alternator is going to be activated and go into charging mode (read below)

OPERATION
The amount of direct current produced by the generator is controlled by EVR circuitry contained within the PCM. This circuitry is connected in series with the generators second rotor field terminal and its ground.

Voltage is regulated by cycling the battery positive path to control the strength of the rotor magnetic field. The EVR circuitry monitors system line voltage (B+) and battery temperature (refer to Battery Temperature Sensor for more information). It then determines a target charging voltage. If sensed battery voltage is 0.5 volts or lower than the target voltage, the PCM grounds the field winding until sensed battery voltage is 0.5 volts above target voltage. A circuit in the PCM cycles the battery positive (high side) of the generator field up to 400 times per second (400Hz), but has the capability to ground the field control wire 100% of the time (full field) to achieve the target voltage. If the charging rate cannot be monitored (limp-in), a duty cycle of 25% is used by the PCM in order to have some generator output

 

Is it possible that the fact that the camper batteries are connected to the driver side battery is causing some sort of voltage drop to trigger this?

 

very possible. i would get an isolator installed so it don't back feed OR put a cut off switch on it when not in use

 

I have a bidirectional combiner switch right now that joins if the voltage is high on either side.

I was thinking more about moving the + charge line to the passenger side battery.

 

I don't think it will matter where the connection takes place as the batteries are tied together.

The ECM monitors voltage/temp off the drivers side battery and the charge hits the pass side first.

I would verify the batt temp sensor under the drivers bat is in contact with the batteries.

All in all your voltages sound just like mine.

 

You mean buy an external regulator and bypass the pcm control?

 

I can't find any information about using an external regulator with the 3rd gens. Anyone done this before?