That's interesting. Thanks for the info.

My apologies to the board. Turns out the fan clutch relay I was referring to is for the gas trucks. The diesel doesn't have a relay for the fan clutch. I'll have to do some more digging.

 

Thanks Dmaxeter, I went out and looked at the clutch and thats cool!!!! I assumed that it was thermostatic, If thats not pulse width modulated it should be no problem to temporarly engage. I have a queston now, are these fans supposed to come on when vehicle speeds are say 50 mph or so?
Cummins really sems to have it together, makes me so happy when I am under the hood changing the oil I don't see the stuff I see in GM made stuff. Even the new ferd f350 my buddy had, I was thinking to myself " that must have been a last moment thought "

 

Our Macks dont use the road speed for any input on the fan. Just those three things I mentioned. I will have to try it on a truck at work and see what it does. I know it will work, cause you can still get a fan over ride switch as an option even with the electronic viscous fan clutch. GM uses this style clutch on some of their vehicle too. These systems are fairly popular, its jut a matter of popping hoods to see who all does use them and where. Just tell me which wire to supply 12v to on mine and I will be the guinnea pig for all of you guys. I would figure it out on my own, but my sickly crap top caught the internet claps or something and wont open PDF files at this time.

 

Here's some more info:

Pin 1 BR/OR Park lockout solenoid control
Pin 2 DB/DG Sensor ground
Pin 3 BR/LB Fan speed sensor
Pin 4 not used
Pin 5 YL/PK 5 volt supply
Pin 6 GY/PK Fused ignition switch output (run)

The 2004 shop manual uses the procedure below to test the fan clutch. There are 2 things that make me believe that the clutch can't be tricked into engaging at any time. It says it may take up to 15 mintues for the test which leads me to believe that the fan clutch has to become hot in addition to receiving a signal from the ECM. Also, when performing this test it will set P code 480. So if you want to engage your fan clutch by grounding out pin 1 then you will get a Check Engine Light and code 480.

NOTE: The following test may take up to 15 minutes
to perform.
The engine should be at normal operating temperature.
(1) Set the parking brake and verify the transmission
is in park or neutral.
(2) Set air conditioner (if equipped) and blower fan
to OFF.
(3) Start and allow engine to reach normal operating
temperatures.
(4) Stop engine, connect the DRB III and select
appropriate model year and engine option.
(5) Check for and correct existing DTC’s
(6) Using Tool 6801, connect pin 1 of the electronically
controlled viscous fan drive connector, located
at the lower fan shroud to battery ground.
(7) Using the DRB III, verify that DTC 0480 set.
(8) Start the engine.
(9) Go to the SENSOR screen and observe the fan
speed.
(10) Run the engine at 2500 rpm.
NOTE: It maybe take 15 minutes before fan speed
increases.

 

Well, I gave that test a try. I connected a jumper from pin one, Brown with Orange tracer, to ground and turned the ignition on. I connected my scan tool and found no active code. I went and made sure that the jumper was making contact and it was. Still no code. I said screw it and went down the road in it. Well gaaaaallllllllyyyyy, The fan is locked up. I drove about 15 miles and the fan was engaged the entire time. Never logged a fault and when I came back I disconnected it and within about 1/8 of a mile the fan disengaged and all was normal again. I cant figure out why it never logged a fault. I dont know what long term, if any, effects it will have on the ECU or the fan clutch. I dont see where there would be any since this is how it was designed to work, just I am sending the signal now instead of the ECM. I do know that the engine coolant temp was significantly lower and the throtle position was significantly closer to the floor. It does seem to take more fuel to turn the fan but that is to be expected. I dont see why one could not wire in a switch and have themselves a manual on off clutch. I know I am going to do it. And there was no 15 minute wait. As soon as the jumper was installed, the fan came on. After disconnecting it takes a few seconds for the clutch to disengage but nothing to worry about. I dont know if cooler ambient temperatures will affect how this operated due to the viscous oil or not, only time will tell

 

The only problem I see doing this is your fuel mileage is going to go out the window so to speak. I am considering an electric fan very closely. Perty sure I am going to do it. Going to use a relay that will cut in on when the A/C is turned on and it also has a temp probe that I was going to install on my tranny cooler that will turn on when temps get to a preset level. Don't have to worry about a switch then.

 

Yes, this mod will not increase fuel milage or add any additional horse power to your truck. This mod is not for those. This mod is designed to keep an engine cool before and during a hard pull or extreme operating condition. If your looking for milage, go to the next post, this one is not for you. If you are looking to keep the engine temp below 205deg on a long hard pull, then this is for you.

I think I can get a dash switch from work that has a little picture of an engine fan on it when its turned on. I will have to see what I can get and see how it works. I know the light is a seperate 12 volt circuit from what the switch is running so it should work great. Now I need a panel to mount some switches to.

 

https://www.dieseltruckresource.com/...cat=500&page=1

How about this panel?

 

Great looking panel. I do however use that cubby hole but I believe I have an idea that that picture just gave me. Thanks!!

 

hey dmax.did you end up wiring the switch in?if so how is it workin out?thanx for the good info so far

 

I was wondering if anyone is using this mod and having good results,without dtc?