View Full Version : Detailed cooling fan question!!? HELP!!

07-17-2003, 10:01 PM
I have thoroughly searched the cooling problems area and cant find the info I need.

The fan motor works. High, Low speeds(I hot wired it) and I changed both temperature sensors. The A/C plug is disconnected because of the compressor is froze up.

ECU, ECTc where are these and how do I check them. I think the IRCM is behind the passenger headlight (big box with about twenty wires coming out of it?! The wires donft seem to match the fan wires.

I have a simple light probe, and I have BASIC knowledge about electronics. Can anyone tell me how to diagnose the ECU, ECT, and IRCM? This #14 wire stuff doesnft work for me. My wires have colorscnot numbers. My book for the car is SH**!

I donft have a code reader, but I am willing to go purchase a multimeter if I need to. My high speed fan kicked on in-between the M and the red until I changed the two wire sensor. After changing the sensor, the engine temp got up to just past M, and I shut it off. I donft like stressing my engine like that.

Anyones help would be greatly appreciated! In simple English!


07-17-2003, 10:35 PM
Well, the ECT (Engine Coolant Temperature Sensor) is the two wire coolant sensor, which I believe you are referring to. The coolant sensor with only one wire is the sending unit for the gauge in your instrument cluster, it has nothing to do with the cooling system (other than provide the gauge with a reading).

I believe that you're talking about the EEC (aka computer, PCM, brainbox, etc), when you mention the ECU. It is located in the passenger side kick panel of the car, and monitors and controls many functions.

The IRCM should be behind the passenger side headlight, as you said. I believe that my 94 has around 24 wires going into it.

It really sounds that your fans are working properly, and that you're just experiencing the high turn on temps for the fans. That can be changed with a chip.


07-17-2003, 11:00 PM
That is a great start!!! Im starting to put the pieces together.

Only problem... the low speed fan only comes on when I hot wire it(directly to the battery). From what im hearing, it might be the IRCM. I just dont understand how to troubleshoot the unit. I think I need to check two wires commingout of the unit for voltage. Is that correct? if so... what wires, and how do I do it. I would need to trick the computer into turning on the low and high speed fans, and unplug the IRCM to check for voltage?

07-17-2003, 11:25 PM
If I have my A/C compressor disconnected, will the low speed fan still come on with the A/C switch turned on?

07-17-2003, 11:28 PM
I have called Autozone and another parts store, and they dont know what the IRCM is! I thought I bould put a new one on and see if that fixed the problem.

Is this a ford dealor only part?

07-17-2003, 11:37 PM
It sounds as though it may be your IRCM that is keeping the low speed fan from turning on. I don't know if having the compressor unplugged is effecting the operation of the fan. However, for the low speed fan to be turned on via the AC controls, I believe (not certain) that the AC compressor needs to be plugged in. Or you may be able to use a jumper wire in the connector that attaches to the compressor. I am not recommending this, by any means, as this is just a thought of mine, not a fact.


07-18-2003, 12:56 AM
I have read posts from a couple of guys who unplug the compressor and just use the max AC button as a fan switch.
IRCM is probably a Ford Item only , could check out some junkyards for a cheaper option.

07-18-2003, 02:23 AM
Is there anyway to diagnose the IRCM and see if it is actually the problem?

07-18-2003, 07:58 AM
On my '90 SC, the low speed wouldn't come on with the a/c button until the a/c system was repaired.

Remove the connector from the IRCM and look for the numbers. Find wire #14. Reconnect the connector. Cut wire #14 but leave room to crimp it back together. This wire will operate the low speed relay which will power the low speed fan. Fan will always be on when ignition is on.

07-18-2003, 11:07 AM
I by passed all that crap, i used two relays for high and low, a switch and and alot of wirer, i now i just manualy control power to my fan with a flip of a switch it dont turn off untill you turn it off, lets car run cooler. I did the same for my intercooler.

07-18-2003, 04:31 PM
Thanks tripntx
I was wondering where that number thing came from. Now I see!

I would still like to find the problem and fix it. Is there a tester for the IRCM? If I pulled the codes from the car, would it tell me what is causing my low speed to not come on? I want to fix whatever is broken first.

After that, I think I will add a switch to the #14 wire, so I can manually control my fan in heavy traffic or other conditions where I want my engine to stay cool.

Alsoc If I manually override my low speed fan, buy cutting the wire or adding a switch, will the high speed fan still function normally?


07-19-2003, 04:16 AM
I unplugged the compressor when I first got my car because the AC didn't work. I found out soon after that if I turned on the AC or defroster the lowspeed fan would run. The system was absolutly bone dry. The only thing I can figure is that the compressor cutout switch is bad and that would allow the system to operate (minus the compressor of course).

Turbobong, I did the same thing you did after adding a electric fan and removing the mechanical fan from my other car. One day I ran into work to pick up a tool and ended up geejawing with one of the guys that happened to work that Saturday. Well after about 20 minutes I realized that I had not turned on the fan and the engine was still running. By the time I got out there there was steam pouring from the intake manifold right at the head. After replacing the gasket I installed a thermostatic switch.

Duct tape and coathangers are not for repairs. Figure out the problem and fix it. If you don't you will kick yourself in the *** later.

The recent posts on this topic have EVERYTHING you need to figure out why it's not working. Use the search function. Follow basic troubleshooting procedures and you will find the problem.


07-19-2003, 04:52 PM
I think that is the second time you have told me not to do the Duct tape and coathangers thing for my repairs. :D Your not leaving me with any tools!:p I did see the write ups you did on Rad Fan. I have been using some of that info.

News update... replaced the plug, and found that the fan does come on with the A/C. Strange though... It sounds like the high speed fan, but Im not sure. I made sure the wires matched on the plug! I got the colors to match, but the wire sizes out of the IRCM and into the fan are different guages. The exact oppisit of the color??

From my Duct tape and coathangers days when I connected the fan to the battery, the low speed fan seemed slower than it does now:confused:

Also... replaced sensor (two wire one) for the engine control.

But... fan doesent come on unless I turn on the A/C.

Please correct me if I am wrong! If the fan works when I turn on the A/C, then the IRCM and fuseable link must be ok!?

Starting to sound like a problem with the engine control module.

If that is the case, I think I will set up another thermostat switch for the fan. While searching I found a schamatic for this modification.

07-19-2003, 04:54 PM
I donft remember where I got this! But I would like to give credit & thanks to the person who designed it!

07-20-2003, 12:14 AM
Make sure you check the high current wire supplying the relays. My '92 lost the fans when a fusible link near the front of the drivers fender corroded/melted. Replaced and no problems since.

07-20-2003, 02:03 AM
I will check it out, but I thought if my fan came on that the problem must be elsewhere??

07-20-2003, 02:16 AM

If it's working with the AC then it should work when the temp gets high enough. Try unplugging the temp sensor you just installed and run the car. The high speed fan should run in that situation (I think). The EEC turns on the low speed fan when it gets the signal from the AC, so the output from the EEC works. Your engine is probably not as hot as you think.

Another possibility is that you have air trapped in the system, and the gauge sender is hotter than the EEC temp sender. Basically it looks hotter than it is. Air in the cooling system can cause a lot of problems on these cars. The rad is lower than the engine and since water seeks it's own level if you just fill the rad then you have a lot of area that is without coolant. That is the reason the little tube that sticks out of the thermostat housing has a bolt in it, so you can bleed most of the air out of the system. After that just fill the overflow and drive it hard for a few minutes (if your not up to temp already) and shut it off. After that the air will be purged into the overflow and when the system cools it will suck in coolant that the air displaced. It usually takes a coupla times. Make sure not to let the overflow go dry. It's kinda like bleeding brakes but the rad cap is the check valve.

Your link is fine. I am going to post some findings from today working on Vernon's car since he had no high or low speed fan and no power to the IRCM (the black and orange wires I was telling you to check.


07-20-2003, 02:56 AM

Thanks! I thought about weather the cars actual temp was reflected in the stock gauge. Mine was almost in the red before the fan came on. Doesnft leave you with a good feeling! An aftermarket gauge might be a good idea to check the temp. I would like to make sure. I donft want all me duct tape to melt off!! :D

Tomorrow morning, I will bleed my system. That might be everything! Wouldnft that be a kick? I do remember reading something about that in previous posts, but didnft give it much thought.

I will also pull the plug to that sender and see what happens.