Update on manual fan clutch switch

[DMcGalliard]

Hello to all,

There was an earlier thread on this subject and I have just installed the manual switch on my 05. The results were surprising and not expected. Maybe I can get some ideas on how to fix the results.

. I installed it with a 0-2000ohm pot and I have it set to 750 ohms.

. The problem is that as I vary the resistance on the pot it changes the temp reading on the truck as well as my edge.

. At 750 the reading is 225, the fan does come on but you have no clue as to the real engine temp unless you turn the mod off. Then it take a few seconds for the truck temp at show actual, the edge is immediate, the fan goes off.

. As you know my intent was just to turn the fan on and no side effects.

. Is there a way for this to work without the side effects?

. I am getting no engine checks, except as I increase the ohm value above 800 which produces a temp of 230 and the high temp check comes on with the bell ringing.

. I have the pot where I can play with it.

. I suspect that the fan will not turn on except at 220 to 225 because the computer is still controlling it and the pot sends it the signal that it wants. I want the fan to turn on at no higher than 210, and have a true reading on the engine temp.



Help!!!!

Dave Mc

 

[Matt400]

Hi Dave,

The thing is. . what you are doing is modifying the CTS input signal to the ECM to "fool" it that the temp is high enough for the fan to run.



The ECM sees this "fooled" input and commands the fan to run, all the while reporting that input to the instrument cluster module which places the temp needle accordingly so unless you install an aux. sending unit with separate gauge you will have to live with the fooled reading when you have the system on.

 

[redfuelrules]

fan clutch switch

Hello Dave

Where did you tap into the CTS input signal? What color are the wires. I have the appropriate resistors, I just do not know where to tie into the factory wiring.



Sorry for the brief hijack.



It would be nice if there was a way to tell the fan to turn on without going through the computer.



In the mean time, DiPricol has a nice coolant temp gauge that matches the factory cluster. I assume it uses its own sending unit.



Thanks

Ben

 

[Matt400]

It would be nice if there was a way to tell the fan to turn on without going through the computer.

I tried that but unfortunately it causes the CEL to set because the ECM monitors fan engagement to insure it matches what it has commanded.

 

[DMcGalliard]

Hello Ben,

I hooked in out of the EMC at pin 11(tan with black strip) It works except it shows the resistance temp. I am using a varible resistance so I can change it on the fly. When I get it figured out I will probably put in a fixed resistance. It does not seem to throw any codes except if you go too high on the resistance it gives the high temp alarm. Still testing and will post when I know more.

One question is how many stages does the fan have? Is is on of off, at 225 it is full on and raises the rpm to 1000 to pull the fan. So I anyone knows that it has more than one stage let me know and I will try to find the resistance for that stage. :-laf

Later, Dave Mc

Hello Dave

Where did you tap into the CTS input signal? What color are the wires. I have the appropriate resistors, I just do not know where to tie into the factory wiring.



Sorry for the brief hijack.



It would be nice if there was a way to tell the fan to turn on without going through the computer.



In the mean time, DiPricol has a nice coolant temp gauge that matches the factory cluster. I assume it uses its own sending unit.



Thanks

Ben

 

[Matt400]

One question is how many stages does the fan have? Is is on of off, at 225 it is full on and raises the rpm to 1000 to pull the fan. So I anyone knows that it has more than one stage let me know and I will try to find the resistance for that stage

The fan is PWM "Pulse width modulated" so it has infinite stages, the hotter the temp the more the ECM pulses the fan clutch.