house batterys not charging with engine running

Two pieces of test equipment I use that allows me to be in the cockpit and test voltages in the battery box or other places separate from the cockpit are a good clip on test light and a piezo speaker or siren. I use the piezo a lot. Clip one lead to ground and one to the actuation terminal of the solenoid and then go to cockpit and turn the key on and then start the engine. You'll hear the piezo clearly in the cockpit if the circuit is good.

Carry on from there.