The ECC control module operates the a/c compressor and fans via three relays with 12v dc coils that the a/c manufacturer mounts in the roof a/c unit. These leads are brought from each a/c unit and are connected to the ECC Control Module via a four-pin connector for each a/c unit. If you look at your ECC Control Module, J2 is for the front a/c and J3 is for the rear a/c. The corresponding pigtail connectors connect to the a/c units. The pigtail for the rear a/c is marked in red to differentiate it from the pigtail for the front a/c.
On each pigtail, the yellow wire controls the compressor. When the thermostat signals the compressor to turn on, this yellow wire has 12v dc on it. When the thermostat signals the compressor to turn off, there is less than 1VDC on this lead. We tap into this lead to energize a relay which we will use to turn the fan off when the compressor is off.
The gray wire on each pigtail controls the fan - actually the low speed fan. When the thermostat demands that the compressor be on, the fan will run on high speed until the ambient temperature is withing 3 degrees of the desired temperature, then the fan will switch to low speed. So, we want to turn the low speed fan off when the compressor shuts off. Using our relay, we will allow the fan to run (on low speed) when the compressor is on, and then shut the fan off when the ECC Control Module turns off the a/c compressor.
Here is a picture of the ECC Control Module which is usually located under the referigerator.
The DISCOVERY OWNERS ASSOCIATION, INC, was formed to promote the sharing of information and the camaraderie of fellow Discovery motorhome owners. Membership in the club is limited to owners of Fleetwood Discovery motorhomes.