Grunaire Mini Split H4 error code in Heat Mode

I have a Grunaire Mini-Split in a rental unit that has worked well for the last 8 years. It ran great all summer in cool and dehumidifier mode. I just switched it to heat to check on the performance and the unit immediately turns off and shows an H4 error. I have contacted a number of HVAC contractor errors and they do not want to mess with it as it's not one of the top brands. I have also searched the web for the H4 error code. Grunaire customer service doesn't exist that I can find. Any clue what this error is or where I can locate the error to pass along to one of the HVAC contractors in the area?

The unit is Model GSI241HXD Grunaire

Thanks,

Sean G

source https://hvac-talk.com/vbb/showthread.php?2223266-Grunaire-Mini-Split-H4-error-code-in-Heat-Mode&goto=newpost