View Full Version : 1990 SC Cooling Fan Wiring Diagram needed. Also need advice on adding additional fans

06-27-2017, 04:06 PM
I'm finishing up overhauling / modifying my 1990 T-birdís engine. The original owner chopped off connecting plug of the engine cooling fan wires and joined them together using black tape. I need the wiring diagram for the cooling fan so I can join the correct cables together until I buy a new cooling fan motor. Also I want to install additional fans for the Intercooler and condenser respectively. How do I go about installing these additional cooling fans? People have told me I need to install relays for the additional fans. Is this true? Any advice will be greatly appreciated. Thanks in advance.

06-27-2017, 04:32 PM
Early Model Fan Wiring Colors:

Brown/Orange - Low Speed
Brown/Yellow - High Speed
Black - Ground

What are those two joined wires connected to now?

Whether or not you need to install relays depends on if you want to put the wiring and controls back to original or not. Is the IRCM still there and working (small black box in front of the airbox, behind the pass side headlight)?

I run a fan on the backside of my intercooler that is wired to a relay nearby that taps off the battery and is controlled by a switch on the left side of the steering column bezel. Not sure I'd bother with another for the condenser, tho...

06-28-2017, 02:47 PM
First of all, thank you for replying to my post. The previous owner for some unknown reason, decided to eliminate the fan plug completely and then rejoined the wires manually (no connectors) and covered them with black tape. I will buy a plug and restore the wiring to their original state later on. At this moment the fan is disconnected because I just finished some modifications / overhauling I made to the engine and I had to remove the cooling fan to install a new Radiator. Now I just want to fire up the engine and make sure it will not overheat when I reconnect the cooling fan.

Regarding the IRCM, yes, the car still has the IRCM (at least it is still there). However Iím not sure it is working properly. Iíll know once I properly reconnect the cooling fan and fire up the engine. Before I pulled the engine apart for modifications, the fan was just working on low speed. I also installed a new fan switch (the one on top of the DIS on the passengerís side) just to eliminate any doubts that the sensor will send the signal to the cooling fan once I fire up the engine. I will probably end up following your approach for installing the fan in the back of my intercooler as it sound like it is working fine for you. What kind of relay did you used (specifications)? Also, is there another approach to connect the intercooler fan using the IRCM? Thanks for your advice!!

06-28-2017, 03:45 PM
>when I reconnect the cooling fan.

Do you have a code tester? With the fan wired up stock, the first part of running codes involves running the fan, first low, then hi...they're done fast, so you have to pay attention.

>What kind of relay did you used

I used a standard 12v 30 amp relay - find one online or at your local auto parts store.



I would not bother using the IRCM to control an intercooler fan along with the main fan, if that's what you're asking, but I suppose there is a hot wire to it that would work as a key on source. You want the intercooler fan to run constant to do any good. Wire it up with or without a switch, your choice, but again, powered with the key on. Since I used a rocker switch inside the car, I found a key on source there, and then ran wires to the relay mounted next to the intercooler. Hot for the fan thru the relay comes direct off the battery, which makes for a nice short lead, etc.. See the first link below for an image showing the relay at the IC.


Search here for existing threads, such as:

06-28-2017, 07:23 PM
Great info here. Thanks!!

07-21-2017, 10:18 AM
So I bought a code tester and when the computer start testing stuff, I only hear the fan once. Based on your previous reply, I should observe that the cooling fan will be tested two times: one for low speed and one for high speed. Right? If I understood you correctly, then it seems that the IRCM is bad since I only hear the fan once? Also, it seems that the high speed is the one that is not working properly.

07-21-2017, 01:14 PM
So I bought a code tester and when the computer start testing stuff, I only hear the fan once.

The two speeds are applied quickly, one right on top of the other, then both off, so it's hard to detect them both and they seem like one, but at least you've confirmed computer control and basic ICRM & fan operation.

If you want to test fan speeds independently, you can pull the connector at the fan and probe each with a volt meter, then retest, or...

- Find/pull the IRCM and temporality remove the connecter so you can identify #14 & #17 wires - they should have tiny #s inside... Once identified, replace the connector back onto the IRCM. No need to reinstall the IRCM now, but be sure it is mounted when finished.

- Turn the ignition switch on/to the run position.

- Ground wire #14, the low speed fan should come on (relay and fan connector etc. ok). Leave #14 grounded.

- Next, ground #17 and the high speed fan should come on. If it does, the relay etc. is good.

You can stick a straight pin thru each wire, with jumper leads attached to ground them. Add a dab of silicone to the wounds to close them up when done.

If the relay checks out, it is not being triggered, but I think you've already confirmed that is ok, so if no joy with either speed, the relay and/or that circuit inside the IRCM has failed.

But again, the code tester check will run them both back-to-back very quickly and you may have trouble noticing one from the other.

06-22-2018, 09:57 AM
Changed IRCM and the fan does not come one. High speed and low speed fan work when connected directly to power. Unplugging the ECT turns on the Fan. What else do I need to check? Any chance someone could call me before my head explodes? If interested in chatting, send me a PM and I will provide my phone number.