Engaging the fan clutch???

[Silverbullet]

As I've tried not to blow you guys up with questions I have yet another one. Currently my fan clutch is not engaging for the A/C. This is due to the Cummins ECM running the fan, and the Ford ECM running the A/C. Thus causing extremely high pressures on the system and warm/cold/warm air in the cab.



It was suggested I tap a switched ground into the clutch's Br/Or wire to engage the clutch. This did not work. Is there any way to engage the fan clutch manually until I figure out a way to teach the Cummins ECM that the A/C is engaged?



Much appreciated, TIA

 

[p-Bar]

Silverbullet I think MATT400 did a write on this. You may want to PM him

 

[Silverbullet]

Thanks I'll see if I can find it.

 

[Matt400]

Post 20 & 21 here is what I did on an 03 I had. I have not had the need for it on my 05.



The original idea was to flip the switch for fan engage if slow moving or extended backing of a heavy RV to help cool the trans fluid. Basically you are fooling the ECM into thinking the coolant is hot.

I never did it to my 05 because it seems redundant. If you work the trans hard enough at slower speeds when air flow is low, the coolant will get plenty hot before the trans fluid turning on the fan anyway. On my 03 it worked well, flip the switch and the fan engages!

 

[Silverbullet]

So the reason it's not working is because I'm just throwing a ground into the picture. It would be quite a bit easier if the Cummins ECM just knew the A/C was on and would modulate it's self.

 

[Matt400]

I have not read your other posts, what did you do. . swap a CR into a Ford?

If so what year CR?

 

[Silverbullet]

Yep. It's an '05 CR from a roll over vehicle.

 

[Matt400]

I might have an idea but need a few hours, have dinner planned with friends and maybe will get to look at some circuits later tonight.

 

[Matt400]

Ok. . I have an idea that may work for you.



To make it simple, what you need is to tell the engine controller what the A/C pressures are. This way the Cummins ECM will control the fan same as it would if it was in the Dodge.



The way you can do that is to get ahold of an A/C pressure transducer and harness pigtail from an 05 Ram with Diesel and tap or "T" into the A/C line where the pressure switch is on your Ford.

The transducer has 3 circuits-

• A/C Pressure Signal
  
• 5 Volt Supply
  
• Sensor Ground
  

The A/C Pressure signal is the black with light blue stripe wire on the pigtail and you would connect that to pin 26 of the 60 way ECM connector which if you are using the Dodge harness will also be black with light blue wire. . its the same wire used on the Dodge.



The 5V supply is the pink with yellow stripe on the pressure transducers pigtail and that wire connects to pin 54 on the same 60 way connector, the colors there are the same.



The sensor ground is the last wire- brown with orange stripe and connects to pin 32 of the same 60 way connector, the colors are the same there.



That should do it, the ECM will now read the A/C pressures and command the fan as needed to keep them in check

 

[Silverbullet]

Thanks!!!!!!



I'll look into this tommorow. I know the high side pressure sensor was moved on the line, prior to the condensor, during the swap. In best hopes it may be possible to tap into what is there already?

 

[Silverbullet]

Appartently the plug is still attached to the Cummins Harness. I need to find that and a way to T in a pressure transducer. The only other question I would wonder is will the Cummins ECM be looking for pressure if it dosent know the compressor is on?

 

[Matt400]

The only other question I would wonder is will the Cummins ECM be looking for pressure if it dosent know the compressor is on?

In looking at the circuit it appears the transducer is the only input and this actually makes sense when you consider the less than great A/C performance on the 3rd gens when condenser air flow is low.



System pressures have to rise first before it will request the fan so during that time vent temperatures are not as cool as they would be had there been a circuit telling the ECM that the compressor is running.

 

[Silverbullet]

Thanks so much again. Hmmm. Now how to get the transducer into the line.....

 

[p-Bar]

Get a welder to tig a bung (nut)in the line

 

[B.G. Smith]

Not to hijack this thread but what years have the electric engagement fan. I have looked at mine, 06 and can't see any wires going to it. Thanks, bg

 

[Silverbullet]

Not to hijack this thread but what years have the electric engagement fan. I have looked at mine, 06 and can't see any wires going to it. Thanks, bg

The wires run between the fan and radiator. They come from the center of the clutch, toward the radiator, down the radiator, and between the fan and shroud on the lower driver side. They then come out on the lower driver side fan shroud mount attached to the block. There is a grey plug where the wires attach into the main engine harness. You can look there to find the wires.

 

[Silverbullet]

Get a welder to tig a bung (nut)in the line

That would be far too easy. I need it to be difficult and stressful. :-laf Thanks.

 

[Matt400]

Just be sure the sensor from the dodge is installed in the same location as its calibrated for where its mounted.

 

[Silverbullet]

Anyone have a pic for reference? Here is what I have to work with.



This may be elementary but how much difference will it make if it's not close to exact?



#ad

 

[Matt400]

You want your Dodge A/C transducer in the line that goes between the compressor and condenser.

For this swap you most likely used the Dodge compressor right? What about the A/C manifold pipe assembly that connectes to the compressor. . did you use dodge or custom make lines?