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Fan switch install

Start by locating the wiring harness that hooks up to your radiator. On my civic it was on the very bottom towards the passenger side. It has a green clip.

Cut the wires to the harness (making sure you leave a few inches) but dont take the clip off the fan. Strip the wires a quarter inch. Take some wire you have laying around and make jumper cables directly from the battery to find out which wire on the fan is positive and which is negative. The fan should turn on with the key in the ignition but car off (safety reasons). Splice together a new peace of wire (about 2.5 ft long) using butt connectors to the ground wire on the harness and the other end will be grounded to the chassis.

The positive side of the wire you will have to go through the firewall. So butt a peace of wire to that end(around 5ft long) and set aside for now.

Next you will have to make another wire for constant power. I spliced mine into the green vtec wire, but if you dont have can use any other source of power that is activated with the car in the on position.

The wire that you spliced into the constant power will need to be around 4-5 ft long depending on what source you used.
The next step is to drill a hole about 1/4" into your firewall (i know i know, but you have to do it.) The best place to drill is right above the hole where your throttle cable is. Note: do not attempt to just use the throttle cable hole! It does not work!!! I tried it and the throttle position was fukt....all the time. It will idle at 4k rmp. just dont do it.
After your hole is drilled, feed the positive fan wire (from earlier) and the constant power wire. Make sure you use female speaker style connectors. (well it depends on the switch you bought).

You will have to decide where you want your switch to be. I placed mine by the shifter console. Anyways once you have decided, take your two wires and hook them up to your switch. Note: The positive wire from the fan is called "lead" and the constant is just "power". Once those two wires are hooked up, you will have to ground this switch to the chassis.Note: this explanation applies to the "light up" switches. You know the kind that have a little LED light in them. If the switch you purchase does not light up, the some of this info will not apply to you. Im sure you can also use toggle type switches.

write up by red_ef9si from
4G Addict

Fan switch repair #2

The above post is one way to fix a fan problem. I have done something very similar to this before. I would suggest that fixing the problem is easier.

Try this first:
1) Crimp MALE spade connectors onto one end of a few feet of wire (16 -18 gauge) and strip the other ends to make a test harness.

2) unplug the factory fan plug (green) and insert the spade connectors. touch the bare wire ends to the battery. If the fan spins, good!

3) Plug the green fan plug back together.

4) 90% of the time, if the fan works then the problem is the switch on the back of the block. It's the big brass thing with the round bullet style connectors. I just remove and replace it with a new one.

If this does not fix the problem, check for bad connections.

is it recommended to get a new thermo switch or a used one at the junkyard?
car keeps overheating and radiator fan wont go on.
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