Lance9386

This issue is not constant, it comes and goes. I replaced the high speed fan relay and the problem went away for several months, the issue is back again. I assume that if I replaced the relay again it would be fixed temporarily. Anyone have any idea why this relay would be going bad? Can someone describe a simple solution to wiring a toggle switch to the high speed fan? I read a few threads on this but was unable to get it working, maybe because the high speed fan relay is defective. Any advice is greatly appreciated I am getting ready to take a trip in this car and need my fans to work, thanks!

Lance9386

Reference the following Cooling Fan diagram:
http://iihs.net/fsm/?dir=40&viewfile=Cooling Fan.pdf

Suspicion of bad high speed fan relay.

Okay, to bypass the relay I tested connecting pin 87 and pin 30 on the high speed fan relay to get power to the fan for high speed operation. The fans do come on and run this way with the ignition switch in the On position.

Before this I accidentally hook up pin 86 and pin 30, blowing the 15amp fuse inbetween the high speed fan relay and the pcm power relay causing the car to continuously turn over but never run. I replaced the fuse and the car will now start but is running rich. I am going to reflash the car with my handheld tuner to upload the tune fresh. Could this have caused other issues that I may not be aware of?

Is there anything wrong with doing it this way? Using this method, I can have my switch turned off and if all relays are operational the system should still work as designed. This will just give me the option to still engage the fans if the relay(s) are not working properly.

During the testing I was using 14 guage wire, holding the wires together I noticed that the wires were too warm, I assume I would need a larger guage wire to carry the current but I want to hear opinions on this setup.

Ideally, I would like to fix whatever it is causing the relay to intermitently function properly, maybe a bad PCM(Power Control Module)?

I am needing to take this car on a long trip soon and really want this reliable.
Should I add a fuse in the line that I will be running to a toggle switch inside of the cabin? (The line that will connect pin 87 and pin 30 to provide power to the fans).

157dB

Not sure of whats going on here.
A test light would tell lots when the problem arises...

Lance9386

I have no problem pulling out the test light whenever the problem occurs.. If I knew exactly what to check, any guidance?

I am going to try grounding pin 86 this afternoon to see if that will trigger the high speed fan relay into action. Does the car have to be up to operating temperature for the pcm relay to send power to the relays or should this work with just the ignition on and a cold engine?

Lance9386

Any idea which temp sensor could be the culprit? I'd like to order it and replace it just in case.

Lance9386

Forgot to add this detail, when the MAX A/C is engaged the fan will still not engage. When the problem is happening that is......

157dB

yOU ARE LOOKING FOR GROUND ON PIN(S) 86 WHEN THE pcm IS CALLING FOR FAN.
fricken caps lock...

Test light clamp on the positive batter terminal.
Check pin 86 of the low speed cooling relay when low speed cooling
is demanded by the PCM and pin 86 of the high speed fan
relay when the PCM is demanding high speed cooling.

In retrospect, if the PCM is requesting low speed and you have
the high speed relay bypassed with a switch, the fan might not
like low speed AND high speed at the same time...

The vehicle must be hot enough for the temp sender
to report high tems and the PCM to activate the relay.
Sometimes the AC will override the temp sender...

Not 100% on the Ford logic inbetween the ClimateControlModule
and the PCM in reference to cooling fan requests.

Lance9386

Ok, I grounded the pin for testing. With the key on, car not running, and a cold motor, the high speed fan runs. The high speed fan relay is very warm, I would even say hot, no other relays are near this hot... I don't know what the norm is though, what you think?

157dB

Do a pre and post relay voltage test (between 30 and 87) with the
cooling fan running and compare the voltages.
(Do the 85 to ground on the hi speed relay to make the fan run).
A drop of 0.5Volts across the relay contacts indicates bad contacts.
The excessive contact resistance and/or the coil are producing the heat.
A volt drop test will confirm bad contacts.
Then do a volt drop test inbetween the battery positive terminal and
the positive high speed fan power wire at the fan motor with the fan
running. No more than 1 volt of drop is acceptable.
Check the fan connector out at the fan for corrosion or signs of excessive heat...
As the voltage goes down, the amperage increase and thats what burns
up the fan relays....
Not sayin thats whats a happin to ya, though...

Lance9386

We'll see how it goes, I've got the switch ran, works great. If the problem arises again I will post it.