Engine fan does not come on after replacing relay switch

Bypass the relay with a piece of wire, (preferably fused). This means: Remove the relay and put the piece of wire in place of terminal 30 and 87 in the cavity where the relay lives. Even if you don't use a fuse all you are doing is giving the fan the same voltage it would be getting if the relay was closed. If the fan doesn't come on then leave the jumper wire in place and smack the fan motor with something like a screwdriver handle or small hammer with the voltage applied and see if that makes the fan come on. (Stuck fan- replace fan). All electrical diagnoses should come from the relay. It gives you the input and output for the fan. The input is 12v hot on terminal 30. This usually this is constant hot wire from the main buss line on the fuse box. The 87 terminal goes to the fan itself so that the output of this terminal will be a grounded motor waiting for voltage. The 86 wire on this relay is normally fed through the fuse box via the fuel pump fuse and gets voltage when the ignition is turned on. The 85 terminal on the relay is the field ground and energizes the relay. This wire comes from the switch which in this case is the computer or ECM. When the engine gets hot the coolant temperature swich sends a signal to the ECM to ground the relay terminal 85 which colses the points of the relay and allow power to travel from the 30 terminal to the 87 terminal. this gives power from the 30 terminal to the fan at the other end of the 87 terminal. the grounded fan receives this power, begins to spin and cool the engine. By the way relays have a failure rate of about .015% so the problem probably isn't the relay itself. Joe

Did you check the fuse?