I thought of that too. but do you think that 12volts would have caused it to go anyways? i can pull 5volts off the ecm... it would be more worthwhile if I saw a result of some kind or positive proof of how the signal tells the clutch to engage. i mean common... 5 wires for a fan clutch??? hopefully someone will chime in who knows specifically how the ecm and fan communicate and what the clutch is looking for exactly to kick it over.

if i made it... it would have two wires. positive and negative!

it has to get all the reading probably from a water and oil temp, speed probably has something to do with it, RPM...i imagine all these reading go into when the ECM kicks the fan on. Not to mention the air conditioner kicks the fan on...

Darn electronics :D

there has to be someone that knows how to kick this thing.

does the fan clutch have its own 12 or 5 volts going to it constantly??

the fan has its own 5V supply, it is needed for the sensor. Hopefully you didn't put 12V to that pin.
The 5V's are needed to supply the fan control.
The fan adjusting voltage is lower than that.

Camotanker do you have the wiring to the fan, the fan itself and the ECM? If I have access to that maybe I can help you. Doin' that crap with RADAR, Engagement control and missiles all day.:w2:

Simple reason for not throwing any codes- you cut the wires.

Maybe it is cheaper to install an additonal fan from the Junkyard, than messing up with the ECM. Thats what I would do.

To generate 5Volts is simple, you just need a 7805 IC: input with 12V,output is 5V and the connector in the middle is ground -expecting costs: 20cent?:w2:


Whoops! Just saw you poweroutput of 740hp. Impressive! Does your fan operate right know? I will be expensive if the fan won't work!!!
I wouldn't mess up the fan control at this poweroutput. Much to dangerous!


Pin 1: Could be 12V or ground? Thats the reason for the needed diagram
Pin 2: Ground
Pin 3: regulating fan voltage 0V up to 5V
Pin 4: empty
Pin 5: 5V Supply voltage
Pin 6: 12V
All connectors (excluding Pin 4)have to be supplied

Hey bud,
the good news is the fan isn't fried. I turned to HVAC to the AC settings and I hear the fan working at low rpm. So it's not jacked up. I would still like to get this on a switch if possible and I don't have any wiring diagrams. I just figured there would be a simple way to bypass the sensor or to have the sensor engage on demand.

Any thoughts? Supply 5volts to the 5volt wires?

In my opinion it should be possible. There is just the need to isolate the original wiring from the add-on switch to avoid interfere with the ECM.
The 5V voltage is very common to run those devices. The fan speed adjusting voltage seems to be lower than 5V. Usually its between OV and 5V.
I assume you want the highest fan rotation with the switch in the on position?
If so you have supply 5V to the Pin 3 sensing input.

It would be the best way to measure all voltages during use. One time with the fan off, and a second time with the fan engaged. Keep a notice on all voltages at all pins.
with that list it is very easy to apply the correct voltage to the right pin.

If you don't have a digital multimeter ask a certified electronic tech. It will be a lot cheaper than to replace the fan and the ECM.
Try to get the wiring diagram, it is very helpful to know where those cables come from.
The reason why I ask is simple. If the ECM uses digital codes, you can't simply add another volltage without causing big trouble.
:c:

Very good post! SHITTY design...just had my cable chewed up by the fan today in two places so i can't re tape the wires....@#$%^&*()_ the truck starts up fine...i thought i smelled coolant on my way home[no drips]. What would happen if i ran the truck without the wire? Oh and i removed the metal housing[from wire] a way back cause it put a hole in my radiator. I had it secured good but i changed my radiator 2 weeks ago and i guess i didn't secure it right:s:

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Well i drove the truck for a while and everything was ok! I read on another forum where someone screwed the fan to the housing permanently...what i intend to do