Radiator fan trying to spin HI but fails

[Kardaani]

Hello! I would be grateful if someone could help me with this. Custom is made 2014 and has a problem with radiator fan. When AC is on and engine is running the fan should run hi speed all the time until outside temp drops under about +5c/41F. It worked fine in last autumn but now the fan only tries to start spinning fast and then stops or continues at low speed mode. When car is parked it tries this about once per minute. Duration of the hi speed mode is about 0,5 to 1 second. There are none faultcodes. Does anyone have idea for this? Is the issue in relays, AC unit, PCM module or where?

[Frag]

I would get the aircon gas checked,cooling fan Operation is controlled by the system pressure switches.
I suspect you’re AC gas isn’t quite full enough,and this drop in expected pressure isn’t actuating the switches correctly.

[Kardaani]

Good point, thanks! Never even thought about it. I have to go to the AC service hoping that will fix it.

[Kardaani]

The AC was serviced today but they didnt find anything wrong. No faultcodes, leaks or anything. They only added 100grams of refrigerant gas but no change to the cooling fan.
Does the radiator fan has own controller unit, or is it the PCM or other module that runs the fans?

[Altransit]

There is a fan controller bolted to the radiator cowling, this can be faulty (I've had one) or it could be worth checking that the fan is free to turn and isn't partially seized

[Kardaani]

Thank you. I have to check that controller. Maybe the controller gets pulse from somewhere to start fan hi speed and relay inside has lost "keep" circuit. The fan itself spins great. Reach allmost full speed for that short second time, then loss of power i think.

[p2thed]

2.0 ltr and 2.2 wiring diagrams might be helpful

[Kardaani]

Sure they are. Great! Many thanks to you.

[Kardaani]

I figured out today the "Hi speed cooling fan relay" loses controlvoltage for relay coil. You can hear and feel it with finger when relay connects and disconnect one second later. I replaced the relay with other but didnt help. When looking p2thed posted wiring diagram, it is PCM whitch controls the relay. Its time to Ford service now i think.

Thanks for the help everyone.

[Altransit]

Have you checked that the compressor clutch is engaging? If not, the fan won’t stay running.

[Kardaani]

Everything else in the car works perfectly. No fault codes. AC works so i think the compressor clutch works fine too? The AC runs and cools cabin normally even when outsidetemps here has been +28c/83F.
Only problem is the fan. I havent take the call to Ford service yet but it might be easiest way to change PCM and try.

[Kardaani]

There is a fan controller bolted to the radiator cowling, this can be faulty (I've had one) or it could be worth checking that the fan is free to turn and isn't partially seized

There are two boxes on radiator cowling. Other contains 50A fuse for fan and other is actually resistor for "low" fan speed. Today i tried to fix HI speed again and noticed that the LOW speed doesnt work anymore. So the fan isnt spinning at all now. Removed the resistor and figured out that the wire on it was burned cut.
It was ok few weeks ago when the fan still spinned LOW speed but it might had some problems all the time. Now i hope this is the main reason for HI speed failure too.

I visited Ford dealer to buy new resistor but its not selled separately. Only comes with whole set of new fan, plastic housing, resistor, wires etc. prised 350€/270£. After that visited few spare part shops but nothing. Then long googling and nothing but some used parts from ebay.
Resistor is made by Bosch and partnumber 3134503095

Any ideas where i could find new one?

[Altransit]

I didn't actually take mine apart to have a look, I just replaced it, at the time, but if it's merely a resistor, can you not purchase a new one from ebay and solder it in

[Kardaani]

Basically yes, but its not that easy. It isnt a small electronic resistor what you can change by soldering. Current going through the resistor is maybe 30 to 40Amps and the resistor wire part itself is a heavy duty style wire whitch propably glows red when fan is spinning. Soldering with tin doesnt work, becouse tin will melt away. Heads of the wire should weld to terminals somehow. Also you need to know exact ohms and diameter of the wire etc to make it work.

[Kardaani]

SOLVED

First of all, car has no problem with PCM, connections or anything. Only problem is early mentioned resistor for LOWspeed of the fan. It is broken and the fan never spins, until PCM sets HIspeed ON for a one second. That is also ok, it does this when the refrigerant gas pressure gets too high. Normal pressure of refrigerant is about 900kpa but when the fan is not spinning pressure quickly raises. When it reach about 1900kpa the PCM sets HIspeed ON for the fan. Pressure drops immediately below 1500kpa and PCM sets HIspeed OFF. After that it loops, when fan is not spinning and pressure raises again PCM does it again and again forever.

But if LOWspeed of the fan is working, refrigerant gas pressure never raises too high and there is no need for HIspeed mode.

Now my only problem is to find proper resistor for the fan and everything works again. I have made lot of work to find resistor but there is no-one in the world who could sell me that Bosch made part itself. Bosch car servise companys x 3, ford dealers, spare part shops, Bosch importer.. all asked and no. It looks i have to buy 270£ full fan system from ford or build myself something with resistor wire.

Anyhow the "problem" is solved and just for info, i made this all clear with forscan livedata tool.