cat engine not charging house batteries

[MBMyers]

The freightliner dealer said the Cat engine is not charging the house batteries while driving on our 07 Pacifica. I believe the device (for lack of a better word) that receives the power and than sends it to the house batteries is located in the right rear compartment next to the inverter.
The engine is sending out the voltage but the batteries are not getting it.
Any idea's where to look.

Thanks
Mike

[Gorlininc]

You should have a solenoid between the house and chassis batteries. There will be a red cable wire from the chassis batteries connected to one side and house batteries on the other side.
The solenoid coil is controlled by and IRD black box.
When the chassis battery voltage is above 13.2 volts, the IRD closes the solenoid and connects all the batteries together. Thereby charging your house batteries.
The usual problem is the solenoid.
You can check this by letting your rig run, and check to see if you have 12v on the solenoid coil. If you do. Check the voltages on the house battery. Should be above 13.2v. If not then the solenoid is shot. I hope this helps.