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Jeremy, Certified Truck/Bus Technician
Category: Medium and Heavy Trucks
Satisfied Customers: 3375
Experience:  ASE Med/HD Truck Technician, NATEF Diesel Engines and Electrical/Electronics Technician, EPA 608/609 HVAC Certified, Steering/Suspension and ABS/Brakes Technician
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Hiya Jeremy.. i have a kenworth t-800 last 6 on the vin

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hiya Jeremy.. i have a kenworth t-800 last 6 on the vin 322383. esn y005655 paccar 12.9. i have no engine fan operation. the fan soloniod is working. i can read a signal on my laptop for a/c and fan override input. butt nothing coming out. is the fan operated thru a driver in the ecm.. i cant find a relay for it.. thanks

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There is a fan solenoid that operates the fan. It is powered from the fuse panel under the hood, but grounded out the ECM. If the ECM is showing you are commanding operation for the ground, then there is an issue either with the fuse or with the solenoid itself. I would check the solenoid, mounted on the firewall, to see that it is getting both power and ground then proceed on which side is lost. It is quicker to start there.


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Customer: replied 1 month ago.
yeah Jeremy.. there are no relays on the firewall or in the under hood fuse panel marked fan.. in fact there are no relays on the firewall at all. nothing i can see says eng fan for fuse layout..paccar mx 13.

What year is the Paccar engine? Is it EPA 10 or EPA 13?

Customer: replied 1 month ago.
not sure.. data tag dose not say..i think its a you need any other eng #

It is fully ECM controlled. I was thinking of the T6 series, not the T8 series.

CLICK HERE for a pic of the wiring to it. You have a main power which is the red wire that feeds the power. Then you have the ground for the ECM signal. The other wires are for fan speed.

If I recall, that plug is on the left side of the engine near the frame above the steer tire. It is the plug that feeds all the sensors. Since you only lost the fan, I am leaning to an issue in the clutch itself.

Customer: replied 1 month ago.
yeah thanks.. no i checked fan clutch.. works fine..pulled plug off fan solenoid and hooked my jumper up.. everything is working from solenoid to fan..

Best thing to do is test that red wire. See if there is power with the plug unplugged. Then see when you command the fan that the black shows ground. If so, replace the clutch.

You have the electric fan on the T800 series.

I meant solenoid, not clutch.

I just read your response as well. It sounds like there is a drop in wither the power or ground then. That is where the loss needs to be determined. That is where the wire chasing may need to come into play.

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