5th Wheel Rig..Is His Truck Engine Charging the House Battery?

[akadeadeye]

A family member has a 5th wheel rig and had a battery problem on a recent trip. To make a long story short, he believes that his pick up truck is not charging the 5th wheel battery in between stops. The battery gave out on them and he knows they didn't plug into shore power for two nights, but he thinks the truck should have charged it up on the road. How can he check to see if the truck engine is charging the house battery?

Don

[RustyJC]

He should have 12VDC between pin #4 (+12VDC) and pin #7 (ground) on his truck's 7-pin connector. Depending on the truck, he should check this with the engine running as some trucks have a battery isolation relay that breaks this circuit when the truck's engine is shut down to prevent discharging of the truck's battery.

Rusty

[Army Guy]

You might want to check and see if there is a fuse blown. On my old truck, there is a fuse in the main compartment in the engine for the charging line to the trailer. My trailer btry was not getting charged by the truck, only when plugged in. Thought my btry was dead but took in to test and it was still good. My father in law found the fuse and replaced it and it was good to go, real easy to check.

[Ray,IN]

When the truck and 5er are connected, and truck engine is running, there should be over 13 volts read at the 5er battery terminals-if they are receiving voltage from the truck alternator.

The 5er battery will not receive a 100% full charge from the truck because it is common practice to use too-small charging wire in the circuit.