Normaly the Motorhome builder installs the condensor fan and the relay.
Can you follow the wiring from the fan back to the relay.
Here is the link to the schematics again,since the other link does not work,
The "n" at the end has to be deleted,how it got there, I don't know.
The relay should be the standard 12volt/30 amp ice cube size,1 1/4'' cubed.
You may also follow the wires from the evans valve outside,temp control to the low AC pressure sensor to the relay.
Evans Tempcon, Inc
Then click on electrical schematics in the middle ,half way down the page.
Siggy D.