Most likely the transfer relay K2 or K3 inside the inverter is bad, or the spade terminals (some call them quick connect terminals) connected to them are bad. I had the spade terminals fail on mine several years ago and while I was inside it I replaced all three of the relays, they are about $4 each. I just Googled the number on the relay and bought online. Look at the attached schematic and you will see why it must be the relay or terminals.
The following is for others that may have a problem, with the Heart Freedom 20 inverter. I attached a simple schematic that I created while I was troubleshooting a persistent problem I have been having for over 14 yrs. Every now and then the battery charger function would not work. I found that by giving the inverter a "Fonsey slap" it would start working again, sometimes just for a few days, other times for years.
The symptoms were this. The inverter always worked great. When the charger would not work I work "Fonsey slap" it and after ten seconds it would start charging with a slow ramp up like it should. Looking over the schematic I knew the problem had to be isolated to relay K1 or the circuit associated with it. So I carefully inspected all the copper traces and solder connections using magnifier glasses and a flashlight. Low and behold the solder joint was cracked at the high voltage side of the control power transformer. The symptoms fit the find exactly.
A simple solder repair was made and all is well once again. If this helps someone else please let me know that my time was not wasted in this message.
Thanks,
Rick Martin
Palmyra, WI
