Manually Controling Engine Cooling Fan

[cricha]

2017 3500 4x4. trip through the mountains and desert, pulling 8k trailer. Coolant temps 228+, oil temp 235+ fan does not come on. Dealer says "we don't see anything wrong". Is there a way to manually turn fan on and off with an upfitter switch? Anyone have a schematic of the wire colors and what each wire is for in the cooling system/fan clutch that they would like to share? I did this mod on my last diesel truck, and in my opinion, well worth it. Yes I know these engines run hot, the fan makes a lot of noise and sucks up a bit of HP, and oil temp is a calculated value. THANKS in advance for any input!!

 

[gsbrockman]

I would suggest trying another dealer.

The fan should start engaging noticeably around 217*F.

 

[TConver]

No you cannot manually control it. It is pulse width modulated not simply on and off.

 

[kthaxton]

I would suggest trying another dealer.

The fan should start engaging noticeably around 217*F.

Agreed, mine is quite consistent at coming on around 217.

 

[Cummins12V98]

Agreed, mine is quite consistent at coming on around 217.

HOLY CRAP BatMan, we agree!

 

[kthaxton]

HOLY CRAP BatMan, we agree!

Hmmm, on second thought I think it's more like 218. [emoji6]

 

[gsbrockman]

Hmmm, on second thought I think it's more like 218. [emoji6]

Yeah......mine comes on at 218*F. It’s amazing how that pesky 7 is ohhhhhhhhh so close to the 8 on my keyboard......

 

[Too Tall]

Best way I've found to control the oil and coolant temp is back off the throttle. you engine will thank you and you'll get to your destination about 2 seconds later. I try to stay out of 2nd as it has no TC lockup and heat will rise faster. Lock out in 3rd and smell that mountain air as people pass you up flipping the bird.

 

[Matt_L]

If you really want to control when the fan comes on you will need custom tuning.

I have custom tuning with mine and I have the fan come on @ 200*F. It used to come on @ 217* from factory, but I prefer to keep the engine oil temp a little cooler since I tow a heavy toy hauler with aftermarket tuning.

 

[cricha]

No you cannot manually control it. It is pulse width modulated not simply on and off.

Can you explain what "pulse width Modulation" actually is and how it works? I have not heard that term before. THANKS!!

 

[TConver]

Can you explain what "pulse width Modulation" actually is and how it works? I have not heard that term before. THANKS!!

The PCM does not simply turn the fan on and runs it until it is cool then turns it off. Instead it applies a square wave to the fan. This series of pulses and the width of the pulses control how fast the fan spins from zero up to 100%. Under light loads it might be spinning at 25% but under full AC and high temp it will be close to 100% duty. Google pulse width modulation it is a common way to regulate motors.

https://en.wikipedia.org/wiki/Pulse-width_modulation

 

[Dan_69GTX]

The computer also monitors the pressures of the high side of the A/C and will actuate the fan accordingly.

PWM for devices have been around for years. Been used for torque convertors since mid 90s. (could be earlier than that - I don't remember for sure). Sonax has a repair kit for the convertor solenoid on many transmissions since it wears out.

 

[Ozymandias]

....and the ECM has Command and Return Values, if he commands 500rpm Fan Speed then he want to see a 500rpm Return Signal - otherwise -CEL.
Learned the hard way at deep River fording in Iceland, Water braking the Fan.