Just bought an electric fan for my Chevelle, two wires on it, one goes to battery, other to ground. Want to install a on and off switch to it, can anyone tell me how I can do that ?? Like to mount it under my dash......Thanks
HEY JOHN: I have an electric booster fan mounted in front of my radiator. I have it on a lighted on off switch that I bouught at Auto Zone for a couple of bucks. I wired it in series with line going to fan motor. At one time I had a 16 inch puller electric fan and I had it wired with dash board swich but went thru a relay because of higher current pull. Relay are about ten bucks and come with wiring diagram. Don't worry your mom could do this job....DAVE
Get a Double pole single throw relay, and a Proper in-line fuse for the fan, and a proper Single thow/pole Toggle or rocker switch.
Hook one side of the relay COIL to 12 volts power Through any 1 to 5 amp fuse , The other side of the COIL to the wire going to your Fan on/off switch.
From the On/Off switch, hook the other wire to ground. (Your Switching grounds)
The Center wiper of your Relay (Movable Contact ) Will go to your Fan Motor, the other side of the motor to ground.
The "Normally Open" Side of the contact will go to a proper size fuse, then to power..
If your Kit came with a Thermostat Sender, you can now wire that so the lead goes to the Fan switch where the relay Coil wire comes in, and it will run in "Automatic" when the switch is in the "OFF" position...from the signal from the sender. (Remember: the Control circuit (Relay switch)is switching ground, not power, so as the temp rises at the sender, more ground goes toward the switch...turning the fan on automatically.)
You can also use a lighted switch, or an indicator lamp If you wish the option, It's good to know if the Fan is actually running! Just hook it to your Movable Contact on the relay, the other side to ground.
In line fuses blow like crazy on a 16-inch fan ... I use a fusible link and double relays on mine and it works sweet as can be; no heavy power draw, like when I had a circuit breaker on it, and no fuses blowing, like when I tried an in-line fuse!
In-line fuses are not necessairly evil but have to be the right kind and rated for the load - motor starting, in this case. A fan that pulls 10 amps is going to need at least a 20 amp slow blow fuse to survive. Your generic SAE20 likely won't cut it for that application.
BTW, fusable link in that application really is a pretty good idea.