Hi I recently replaced all my Trojan T-105 batteries and thought the HEART Inverter/converter wasn't working right. I bought a new one on EBay for $300 and then I found out that the Heart was working correctly. The batteries were below voltage and I Have an Echo Charger hooked up to my engine batteries and they were also discharged.
After I had used an extra charger and got the batteries up to over 10 volts the Heart charger took over and all is fine. Heart is warm and fan kicks on once in awhile. My coach and Heart Freedom 10 is 18 years old. Never had a problem with it before. New one is sitting in my shop.
Good luck and hope you get it figured out. Love mechanical stuff. Hate electrical problems.
Busyguy