Lawlor,
I think if it was me trouble-shooting the issue, I would perform the following sequence. Plug the coach into shore power. Check the output from the 30 amp circuit breaker in the main panel identified as "inverter". If 120 volts present, then I would remove the little white cover on the inverter that reveals the romex connections going to and coming from the inverter. With my meter I would check for 120 volts going into the inverter. If present, then check for 120 volts coming out of the inverter. That would prove that the internal transfer relay inside the inverter is passing thru the 120 volts coming into it. If there is 120 volts going into the inverter, and none coming out of the inverter, then either the circuit breaker mounted on the Inverter is tripped or the transfer relay inside the inverter has failed. If there is no 120 volts coming into the inverter, then I would trace that romex backwards to find the open circuit. Perhaps it is this relay that your talking about. I am not familiar with this relay or what its purpose is. It is not on any of the coach schematics that I have looked at. Please advise, Fred