Found what it is. Its a relay for coach to chasiss batteries
https://www.mmrvelectronics.com/prod...e/00-00956-000
Specifications:
Typical Installation Diagram
Part Number: 00-00956-000
Output Current: 3 Amp maximum
Standby Current: Less than 2 milliamps
Ambient Temperature Range: -40 C to +85 C
Normal Input Voltage Range: 10 to 18 volts
Short Term Over Voltage Protection to: +26 volts
Reverse Voltage Protection to: -300 volts
positive Voltage Spike Protection to: +150 volts
Operating Environment: Out of direct weather
Apparently it is designed for furnaces but they adapted it to control charging the house and coach batteries.