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Fan not working

I've noticed that the water temp is getting quite high while driving in town. On the highway it stays in the normal range but when in town idling it can get up into the red.

I've run wires directly from the battery and both fans work but when I've stopped the car, while the temp is high, neither fan is working.

So what's left? Temp sensor, relay, fuse... Wouldn't the temp sensor through a code? Where physically are these parts? I've tried tracing the wires but they disappear under the air box.

Fan not working

Reply #1 –
Could be the fan relay in the IRCM box.  The ECU controls the relays for the fans.
Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon-  '81 Granada GL 2dr

Fan not working

Reply #2 –
hmmm! I've done some reading on the IRCM and...couldn't that also explain why the A/C is not working? The fuel pump is still working though!

Fan not working

Reply #3 –
I've never messed with the IRCM's personally (all my Foxes have been pre-86), but it is possible that both issues are caused by faults in the IRCM.  Time to do a little testing, or dig up a spare to plug and play.
Long live the 4-eyes!  - '83 Tbird Turbo - '85 Marquis LTS - '86 LTD Wagon-  '81 Granada GL 2dr

Fan not working

Reply #4 –
WOW! $214.00 for a new IRCM at the dealer - garage price. I thing I'll hook up the fans temperorary to a switch and an external relay direct to the battery. I'll start probing wires to see what's going on. If the problem is in the IRCM I'll rebuild it over the winter.

Fan not working

Reply #5 –
Why not just wire a relay into the fan and use the ECM's output to turn it off an on? If I'm not mistaken, the ECM outputs a ground to turn the fans on and off, so if you wired a relay and used the ECM's output as the ground it should work just like the IRCM did.

Too bad you didn't come up with this problem sooner - I gave the IRCM that was in my parts car away to the guy that bought the engine...
2015 Mustang GT Premium - 5.0, 6-speed, Guard Green - too much awesome for one car

1988 5.0 Thunderbird :birdsmily: SOLD SEPT 11 2010: TC front clip/hood ♣ Body & paint completed Oct 2007 ♣ 3.55 TC rear end and front brakes ♣ TC interior ♣ CHE rear control arms (adjustable lowers) ♣ 2001 Bullitt springs ♣ Energy suspension poly busings ♣ Kenne Brown subframe connectors ♣ CWE engine mounts ♣ Thundercat sequential turn signals ♣ Explorer overhead console (temp/compass display) ♣ 2.25" off-road dual exhaust ♣ T-5 transmission swap completed Jan 2009 ♣

Fan not working

Reply #6 –
Paul The upper fan doesn't activate till the engine is approx 210* and the lower works with the AC and if the temp is 225*(both would be on at that point). The Temp gages often lie on these cars, I've seen the gage at max before the fan would kick on... If you jump the A/C pressure switch(disconnect the compressor, as I'm sure the system is low on refergerant), and turn on the A/C the lower fan should run. A easy way to check the IRCM is to run codes and watch the fans(you may have to do it more than once as it only blips the relays for 1/2 sec or so). Also if grounding  pin 17(pink wire) 0n the IRCM  brings on a fan(lower I believe) then that portion of the IRCM is OK. I'll do a little studying up on the IRCM and see how the upper fan is activated(I knew but forgot)... OK grounding pin 14(br/yel) should activate the upper fan... I use a test light for this operation as it won't harm anything if you connect it incorrectly. It should dimly light and activate a fan on the correct pin.

BTW I'm 99% sure the late '80s Taurus/Sable uses the same controller...

Fan not working

Reply #7 –
Thanks guys!

I'll let you know what I find.

Fan not working

Reply #8 –
OK! With Pin 17 gnded (pink wire) the small fan worked. With Pin 14 gnded (br/yel wire) the big fan did not work.

EDIT: Didn't here the relay click.

Fan not working

Reply #9 –
I'll check a little more, but it will be tomrrow... Younger daughter is visiting from Iowa...

Fan not working

Reply #10 –
hmm?

Quote
Primary Cooling Fan Power Relay
                        K4 switches power to the primary cooling fan. K4's contact voltage is sourced from IRCM                        pins 3 and 4, and it's coil voltage is sourced from the K1 contacts. When energized, K4                        applies power to the primary fan via IRCM pins 1 and 2. K4 is energized via a switching                        circuit consisting of Q2, Q5, Q6, and their associated components.
                       
                        IRCM pin 14 is the control input for the primary fan. If pin 14 were open(high), R4 applies                        +12 volts through the R9 current limiting resistor to the base of Q2. The current flowing                        into the Q2 base turns it on, making the collector "low". The "low" applied to Q5's base                        turns Q5 off, making it's collector "high". The "high" thus applied to the base of Q6 turns                        Q6 on, pulling the Q6 collector low, energizing K4, thus turning on the fan.
                       
                        R14 and R12 are pull up resistors which normally pull the bases of Q6 and Q5 high. R11 and                        R9 form a voltage divider that turns Q2 on and off. C4 is used as a time delay that slows                        the turn on and shut off of the primary fan. Diode D4 is a reverse-voltage protection diode.
                       
                        IRCM pin 14 is controlled by an output of the EEC. When the engine is below 190*, the EEC                        applies a "low" to pin 14. The low turns off Q2, allowing Q5 to turn on, causing Q6 to turn                        off. Conversely, when the EEC determines a need for the cooling fan, it removes the low                        from pin 14 which allows Q2 to turn on, Q5 shuts off, and Q6 turns on energising K4 and                        applying voltage to the main fan via IRCM pins 1 and 2. This circuit apparently acts as a                        kind of "failsafe" for the fan; if the EEC wire to IRCM pin 14 breaks or if the EEC output                        "opens", the main fan will run continuously.

If I'm reading this right, a gnd on pin 14 will turn the primary fan off while a high (+12V) or an open circuit turns the fan on.

Quote
If pin 14 were open(high)...thus turning on the fan.

EDIT: What do you guys think? Should I put +12V on Pin 14?
 

Fan not working

Reply #11 –
You may well be correct.. The '88 EVTM shows both the fan relays and F/P relay fed 12v from pin 24. It pictures a voltage inverter(block diagram) on the ground side of secondary relay, but none for the primary fan. If that is the case grounding pin 17 should not operate the fan, possibly they are reversed in my diagram??? Connect the test light to 12v then to pin 14... Or maybe I just have my primary and secondary fans confused....:hick:

Fan not working

Reply #12 –
I put +12v on Pin 14, relay clicked, fan worked. I guess that rules out any problems with the IRCM.

It scares me though to see the temperature gauge read that hot. Maybe I'll pick up a cheap aftermarket gauge and put on there to confirm nothing strange is going on.

I could let the car idle in the driveway and let the temp rise into the red and see if the fans do cut in before I warp the head or something.:hick:

Maybe you're right and that the temperature needle in the red is a "normal" thing on these cars and nothing to worry about.

Fan not working

Reply #13 –
If my temp needle rises over half way something is wrong.
One 88

Fan not working

Reply #14 –
It's the same way with the 5.0L bird. I don't know if I ever noticed the temp in that one go over halfway. But with the TC it can touch the red but the fan doesn't cut in. I'm afraid to let it go any higher.