I wanted to be able to turn the fans on and off whenever I decided. So I went with the Voodoobox mod. Originaly I had a switch that lighted up, so I Connected the wires coming from the relays, ground, and constant 12v to run the light. I put the ignition on, flipped the switch and evrything worked.

But the switch broke, so I went with one of those flip switches now the wierd problem. If I connect the Relay wire and ground to the switch the fans come on. Flipping the switch does nothing. But if I connect the Relay wire and Constant 12V wire it turns the fan off. So I am not really sure what to do. I want to be able to turn the fan on and off at will. Could someone please help me?

 

What type of switch is it? (single pole-single throw, single pole double throw)

How many terminals does the switch have and what are they labelled?

Most likely just a different type of switch and you may not be wiring it up correctly.

 

It's a single pole-double throw. It only has 2 terminals, and they are not labeled. I have tried swiching the wires back and forth, but the fans start with the ground connected. When I connect a 12v wire to it it shuts the fans off. It's just wierd....

 

Why is it so important to get the switch to light up?

Wouldn't you want the switch to ground both the light and the relay? In other words, the switch doesn't touch the 12v power wire at all, but rather is spliced in between the light's ground wire and actual ground? That way, neither the fan's circuit, nor the light's circuit, is complete until you flip the switch.

 

Shouldnt a single pole double throw have three terminals?

Sounds like single pole single throw, which means the terminals would be connected when the switch is in one position and open circuit in the other position.

Get a multimeter and measure the continuity between the terminals with the switch in both positions - if you get a continuous circuit between the two terminals no matter what position the switch is in, then it's a bum switch.

 

For my fan mod, I used an illuminated red pushbotton switch, mounted on my dual A-pillar in the face next to my boost gauge. Unfortunately I blew the LED because the terminals werent labelled and my guess as to the polarity was wrong. It will look pretty cool when I get around to fixing it one day......

I actually use it now for my foggies coz I didn't notice much change in temp with the fan mod so I disconnected it. Couldnt get an OEM fog switch, so my red nitro switch was the next best option, as it was already in there.....

 

It can be a good thing to make sure you don't walk away from the car with the fans switched on; only to return to a dead battery.

 

but i like dead batteries!

actaully i use light options to be wired in the circuit. that way, i know 1) the switch is on and 2) the item is actually working (ie using power). hate to have me think the fan is running when it really burnt out.

 

Maybe I do have a single throw, but technicaly if I connect the wire coming from the relay to the switch and ground wire to the switch it should turn off and on according to the voodoobox site. The 12v I'm assuming has nothing to do with this switch since it's one that does not light up.
But I just can't understand why it starts when I leave the ground wire connected, and when for fun I took the ground wire off and put the 12v in it's place the fans shut off? Should I get a switch that has three terminals on it? I do apprecaite the responses so far!

 

Maybe you tapped into the wrong side of the relay? The key word for this mod is GROUND. The relay terminals already have 12v. You want the ground wire for the switch on the relay. Basically, when the ECU needs the fans, it will ground the switch (85 on the relay I believe) which will connect the high current side (87 and 30). The fan switch lets you bypass the ECU and ground it yourself with your switch.

There should be 4 pins on the relay (maybe 5 on relay #1 if I remember correctly):

A B

C D

When c is grounded, the circuit of A->C is closed causing the the internal mechanical switch to connect B to D. Thus, power goes to the fan.

Checkout http://www.mgcars.org.uk/electrical/body_relays.html for more info.

Btw, if you only tap into relay 3, it will run on med I think- that's what I did. Works well enough with one simple wire and a switch.

 

Lets just clarify this - you've got a switch with two terminals. When you connect ground to one terminal, relay wire to the other, the fans turn on regardless of the switch position, right? And if you connect 12V instead of the ground, the fans turn off, regardless of switch position?

I'd be interested to know if the fans turn off when you disconnect the ground wire from the switch, or when you connect the 12V wire to the switch.

What I would do.

1. Get a multimeter and just verify that the switch works. Will only take a few seconds, very very easy to do.

2. CHECK that you've got the correct relay wire. Use the wiring diagram from www.iluvmyrx7.com to help you sort out colours etc. Note that each relay has four wires, two of thicker gauge. They are high current wires for the fan. You are interested in the thinner control wires. Each relay has a thin black/yellow wire - it is 12V from the ignition switch. The other thin wire (few diff colours) is the wire you want to ground.

NOTE - some of the wires in my car werent the same colour as specified in the wiring diagram, so I used a multimeter to figure out which was which.

Once you've found the wire(s) you want, ground them in the engine bay with the ignition on to make sure the fans come on with the wire grounded, and turn off with the wire not connected to anything. Then connect them to your switch so you can ground them at will by flicking the switch.

Piece of cake.

If it still doesnt work I'd then start testing the relays to make sure they are working as specified.