I need help finding the source of my problem. The problem is the seconday fan does not engage when the A/C is activated. I will be replacing the fan motor (it's old) to eliminate that problem, but I wonder what may cause this problem...relays, switches, etc.

Please help, I am getting despearate

 

there is a temp sensor or switch on the passenger side that activates the second fan when the temp gets up there, or you turn your a/c on... I have seen alot of other posts that do deal with this.. you should do a search for it and see what you come up with.