I have a big problem with overheating with my car. Neither fan turns on at any point. I have aftermarket slim line fans which I spliced into the factory harness, but If I hook posotive and negative leads up they turn on. Where would I start to check to find my problem. Also when A/C is on Fan does not turn on either.

This is interesting, because about 3 months ago I posted the same problem with some SLIM fans I have and still have yet to get them to work! First, I tied into the OEM wire harness and they would not command on, then I bought a kit from Summit Racing with a temp probe that I placed through the radiator right below the upper radiator hose, the probe is supposed to click the relay at 190* and turn the fans on, well of coarse, that doesnt work either. If I jump both fans to the battery, + to + and - to - obviously, they will turn on, but I am still having issues with them coming on without battery voltage.

I would love them to be controlled by the OE computer still, even though I have MSnS.

Looks like this post could kill 2 birds with 1 stone, so dont mind me if I chirp in since I have the same problems as you buddy :)

The temp probe kit was going to be my next route, until today I was just wanting to check the 30A fusable link, which I replaced a a week ago to it being blown, and it's blown again. After looking into it further I noticed on the passanger side harness coming from the car which the fan plugs into there is a wire tapped into, the solid blue is tapped and has a wire which leads to a black/white wire in the harness connecting to the A/C Compressor. Anyone have any idea what whomever did this before I baught the car was doing. It wasn't wraped in electical tape so I know its not suppost to be there. Also Would the 30A fusable link stop both fans from working? Any help would be great.

I am not a mechanic by any means but I believe..

The stock fans have a two stage circuit with what I believe is a motor inside a motor. One turns on at 180 degrees and the other at 200 I believe. If you hook up to one circuit you get a fan that works from 180-200 and then shuts off. If you hook up to the other it doesn't work until 200. It is best to run a new circuit from a constant 12v with a temp sensor located near the top hose of the radiator because the bottom hose is too cold.

I didn't figure this out on my own. I had the same issue and wickedesi explained the diagram out of the service manual to me.

Originally posted by zwickyj
Also Would the 30A fusable link stop both fans from working? Any help would be great.

It's very possible.

Like mentioned above, there are essentially two circuits going to each fan. One trips lower fan speed operation, and the other trips high speed fan operation. The FSM has a whole logic table to show which fan runs at which speed for a given set of conditions. The bottom line, though, is that most reasonably priced aftermarket fans are single speed; not dual speed like the stockers.

So, when I installed my fans, I tied the high-speed and low-speed wires together and connected them to the positive lead from the fan. For good measure, I did the same with the grounds, and connected them to the negative leads. That way, whether the stock fan was supposed to be running at low speed, or high speed, the new fan will be on either way.

Anyway, that's how I installed mine, and they've been working perfectly ever since... I hope that helps.

i have a pair of FAL fans and solved this problem with the HKS Fan Controller.
programable standalone fan management, plus it also acts as my water temp gauge.
also has trigger outputs for a Radiator/intercooler water sprayer (think STI)

So Velocita, are you wired into the driver side or passenger side wiring harness for the fans?

Both. Each fan is wired into its respective harness. I kept everything stock other than tying the high and low speed wires together.

EDIT: In other words...

BEFORE


AFTER


On the driver's side, tie the blue/white and solid blue wires together, and the black and black/blue wires together. On the passenger's side, tie the white/blue and white/black wires together, and the two solid black wires together. Obviously, the latter two in each case are the grounds, and those connect to the black wire on the aftermarket fan. The others connect to the red wire.

Originally posted by VelocitaPaola
Both. Each fan is wired into its respective harness. I kept everything stock other than tying the high and low speed wires together.

Thanks for the revamped schematic. That should help a bunch.

Only thing I would point out is that you have the names reversed in your text description of what color wires go with what fan. Not a big deal but it can lead to confusion. Many people think that the main fan on a 420A is on the passenger side but that is incorrect.

The main radiator fan is on the driver's side. Many times this fan only comes OEM with a single speed motor in that position. That is the fan that first turns on when the ECU calls for cooling (assuming the A/C is off). I believe this is a 2-speed fan if you have an auto tranny. It certainly is only a single speed on all the MT 420As I've parted out.

The fan on the passenger side is the condenser fan and it will always have two speeds. It will run as soon as you activate the A/C regardless of coolant temperature. It will also run as required in other (non-A/C) circumstances as called for by the computers.

I don't know why but everyone gets these two fan names backwards as to whether they are dealing with the main cooling fan or the condensing (A/C) fan.

Also should point out that the fans for the 4G63 motor are not wired exactly the same as for the 420A but the basic procedure to wire in an aftermarket fan would be the same.