house batteries go dead while driving

my house batteries went dead traveling from Maine to Florida. I checked the voltage at coach battery, with engine running, at 14 volts, at house batteries 12 volts. If I go into motorhome, and toggle the use/store switch from use, to store, then back to use, I get 14 volts to house batteries. ?????
Any ides
I had replaced the relay. I was in contact with RV Custom Products tech support. I finally found a jumper from my BCC board to the charge/boost relay, was on the wrong terminal.