[mycbarnes]

Attached is a picture of the heat exchanger fan relay on my coach as promised. The Bosch relay is in rear engine compartment cabinet drivers side.  Bosch 75 amp relay is the black unit bottom center of picture. To the right is a small circuit breaker can that auto resets. On the relay, power from the 12v buss is the red wire via the breaker. Green wire goes to the 12v heat exchanger fans. Orange wire on relay is the 12v positive control lead for relay coil. Black wire is ground for relay coil. The control circuit for the this relay goes up to the remote starter switch. I have not ringed out this part of the circuit yet. So the answer is that on my coach, the fans are supposed to come on when ignition is on. newer coaches move to a thermostat circuit. Which saves wear and tear on 12v fans and power hog. Having no dash hydraulic fluid temperature gauge in a coach to indicate that this early type circuit of 12v heat exchanger fans system is not working properly makes me suggest to all that it's something to make sure is working properly. The fans when on are pretty easy to hear, key on, engine not started yet.