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spankyjr1, Journeyman
Category: Medium and Heavy Trucks
Satisfied Customers: 2595
Experience:  I worked on all types of equipment semis,forklifts,farm,ect.
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M11, 1997 ,,, 9100 int .. Fan clutch is always engaged with

Customer Question

M11, 1997 ,,, 9100 int .. Fan clutch is always engaged with engine running , however , with key turned to run position but engine not running ( full air ) fan clutch disengages fully till engine is started .... So it works , air switch is fine ,,, but some sensor that only comes into play while eng runs is telling ecm to not send power to air switch , where and what is most common problem ?
Submitted: 1 year ago.
Category: Medium and Heavy Trucks
Expert:  spankyjr1 replied 1 year ago.

Good morning Tony, sorry for delay, my name is ***** ***** you for asking your question, I will try and help you out.

The most likely cause is the ac high pressure switch is stuck closed,90% of the time when fan stays engaged I find this, or associated wiring is the issue,,ac high pressure switch is either on ac compressor small line or anywhere after that on high side line (small line) most times on drivers side after freon goes through condenser. Check the plug on ac high pressure switch for corrosion repair as needed,,if the ecm does not see signal fan defaults to on.

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