Fan relay and switch question

[MrBoxx]

I'm replacing my stock radiator fan with a slim-line fan. I'm just going to hard-wire the fan into the stock fan's wires. My question has to do with the modification that allows the AC fan and radiator fan to turn on at the same time, and the switch that can be installed to override the ECU. I bought a rocker switch with a small LED light to show when it's on. The switch has three prongs, one for ground, one for source (fan power) and one for 12V power. The ground and source look like they're the ones needed for the circuit to switch, and the 12v power looks like it turns the LED on. So, ground and source are going to come from the fan relay, but what should I use to power the LED? Also, on the relay, there are the two prongs that I'll be inserting wires into. Which is the ground and which is the power? I chose a rocker switch instead of a toggle switch because a toggle switch probably wouldn't fit where I need to put it. If someone can shed some light on how I'm going to wire this up, please let me know. Thanks in advance.

 

[grpracing]

I'm replacing my stock radiator fan with a slim-line fan. I'm just going to hard-wire the fan into the stock fan's wires. My question has to do with the modification that allows the AC fan and radiator fan to turn on at the same time, and the switch that can be installed to override the ECU. I bought a rocker switch with a small LED light to show when it's on. The switch has three prongs, one for ground, one for source (fan power) and one for 12V power. The ground and source look like they're the ones needed for the circuit to switch, and the 12v power looks like it turns the LED on. So, ground and source are going to come from the fan relay, but what should I use to power the LED? Also, on the relay, there are the two prongs that I'll be inserting wires into. Which is the ground and which is the power? I chose a rocker switch instead of a toggle switch because a toggle switch probably wouldn't fit where I need to put it. If someone can shed some light on how I'm going to wire this up, please let me know. Thanks in advance.

I would actually add a relay with this switch as well so you don't power the fan all the time and run the risk of the fan acting as a generator when it spins down. Apply the 12v to the power side of the led and then the on lead from the switch to the 12v input of the relay so when the switch is turned on it causes the relay to charge and close the circuit. Then run your power line from the rad fan to the power line of the ac fan so when the contacts are open it is drawing its power from the rad fan circuit. But when off it completes the circuit to the ac fan off the ecu. On the back of the packages for the universal relay it shows the current path so all your doing is breaking the path when the switch is on. Hope that helps.

 

[MrBoxx]

This is basically a graphic of the rewire on the VFAQ:

You must be logged in to view this image or video.

In this configuration, the fans turn on when the ECU tells them to turn on, both at the same time, both at the same speed. The switch is just to override the ECU and turn the fans ON whenever I want them to be on. All I need to know is how to wire the switch so that the LED can light up properly and the switch works properly.

 

[grpracing]

Run the neg to ground and then tape off the relay constant power for the lighted side of the switch. Then run your on position pole back to the energized side of the relay so when you throw the switch your acting as the ecu and that will run your circuit. Only problem with using a spst switch and have it lighted is that if there is constant power to the pole you tap on the relay you will have to make sure you turn it off all the time. You can tap your power off ignition power which will cure that and then just wire the "on" switch side to the switch side of the relay. That would be the safest.

 

[MrBoxx]

Update: Got the slim-line fan installed. It looks awesome, and I didn't have to drain the radiator or take it totally off. I just undid the top mounts and leaned it back to attach the nylon ties. My friend Tim and I jumped the relays and ran a line to a switch in the cabin. I couldn't get the LED to light when the fans were activated. There's something about the way it's wired that it wouldn't work. I may play with it again later, but for now, it's a pretty clean install. I was going to get pics, but I got caught up in the excitement of how easy things were going. Usually my car modification adventures end in me bleeding and broken bolts. Next up, purchase couplers and fab pipes for the FMIC and then I'm done for the year.

 

[generalu]

I know this is an old post - but can anyone suggest a switch, inside the engine bay somewhere, to activate my slim fan when the engine is running (not when key is "on" position)? Please inform. Thanks.

 

[luv2rallye]

Just connect it to the fuel pump relay or to it's own relay which is activated the same way as the Fuel pump relay (via ECU pin 8 going low). It will then only run with the engine turning with ignition.