When I ground the green and blue wires shown here:
http://shbox.com/1/fan_sw_diagram1.jpg
I can hear the relays clicking, but the fans still dont come on. I did this with the key all the way forward but without the car running (cant hear fans over exhaust). Any suggestions?

 

Try it with the car running, I think the relays just switch ground to the fans. Power comes when the car is on.


You should be able to tell when there on when your at the front of the car even with a loud exhaust, should also be able to see the tiniest little drop in battery voltage when they come on, then it should go back up

 

hmm I used that diagram to do mine, and it worked fine you sure you have a good ground source? it should work with key turned all the way forward

 

if you added led's to the switch also you'll be able to see when the lights are on, i used that diagram also. did you use a on/off/on switch?

 

There must be something wrong with the circuit, I jumpered a wire from +12V to D1 and F1 on the fan relays, and the fans worked fine. I simply ran a switched +12V to those connections (removed relays) and I now have a fan switch

 

On mine, I just ground the dk green and dk blue wires and the fans come on with the ign switch in the "ON" position.

 

key must be on for a 93 when you ground the wires. See if power is getting to the fans. Then check ground.



And as for: You cant run switch power directly to the fan. It pulls too many amps. It will burn up the switch and/or catch fire/melt the wires. Thats the whole reason that a relay is used, so the trigger isn't on the same high current side.

 

Sure you can, assuming the switch is rated for the power, and you're using a large enough wire. A relay is nothing more than an electrically operated switch (as opposed to a finger operated switch).

 

It's a bad idea, IMO. Much better to run low current wiring into the passenger compartment than what you would need to power a fan. That's just asking for more trouble. The relay is the way to do it.

 

True...I should have specified that it's recommended to run the relay. Just saying that it is possible.

 

Do you really think that anyone is going to put in a high amp switch and correct gauge wire to do that? Or the fact that they will not figure in the extra resistance of the length of wire to the system. You are just asking for trouble. It doesn't matter if a relay is a switch or not, it's the fact that it's a low current trigger, with a high current side completely separate. It protects the trigger, the component, and the feed all at the same time. When you combine all of that to one source, it's an electrical nightmare, especially for people that don't understand what they are doing.

 

And this is precisely the attitude that causes me not to trust any professional mechanic - "everyone else is dumb as a box of rocks".