Battery Charging Issue

“House bat charges on external and genny power, chassis bat does not” That is normal. It is normal (in most MHs) however for house batteries to be charged when the vehicle is being driven. There is a solenoid, relay or some type of connection that is either malfunctioning or missing.

Ken

house batteries should charge when trundling down the road. There may be a blown fuse, or a failed isolator diode, or a relay with burned contacts.

Chassis battery not charging from generator or shore power is normal. Add a trick-l-start, or similar device.

If you find a BIRD (Bi-Directional Isolator Relay Delay) module then it is the control module for a 12 VDC Relay that connects the chassis battery to the house battery depending on the logic of the moment.

When my house battery got too low from inexperience, the surge through the wiring when the chassis motor started caused the inline fuse to blow. I had to charge the house battery with jumper cables to get back up a bit before the inline 20 amp fuse would hold. The fuse might be on either side of the relay isolator, but if it's an older model I doubt you would have a BIRD

Sounds pretty normal except the alternator should charge the house battery.
Need to find the isolator and check for an open connection.

You can add equipment to charge both directions and still isolate when no charging voltage is present.

Old Fleetwood Montara has a solenoid in the engine compartment on the firewall - when you turn the ignition switch the solenoid energizes and connects chassis/coach batteries. Overtime they start to stick or just fail - it's a continuous duty solenoid readily available at any auto parts store. As I recall if you turn the ignition switch the solenoid should make a disntive click as it energizes - sometimes when stuck a little rap with hammer might unstick it.

If you want to PROPERLY charge a house bank of batteries while driving, please read this ! DC-DC Battery Charging

I just had this problem on my Fleetwood Tioga,as others have said it is most likely the continuous duty solenoid,once I replaced it the house battery was once again being charged from the alternator.

The one I replaced looks like This
Mine was in the battery bay not like the one in the video but the concept is the same.

Here is a video that may be of help

We also have an older (2004) Ford E350 based MH. Low end I guess. Rather than an extra battery isolator it uses the built in Ford auxiliary battery charging circuit which consists of a fuse and relay in the engine fuse box. Look up the details under fuses and relays in the Ford manual.

When I had engine charging of house battery shortcomings I found that the charging voltage was a couple of volts below what the engine battery was feeling. It had only 12 gauge wire but that wasn’t the main problem; it was a connection with a half volt loss, a long wire to a poor battery disconnect switch, rather than a relay, losing another volt.