mcratchet1 Posted 8 hours ago Share Posted 8 hours ago I have an 07 mr688s with a Horton pneumatic fan clutch. Having issues with it constantly staying engaged. What’s the best way to diagnose if it’s a faulty sensor or bad clutch? Thanks in advance Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/ Share on other sites More sharing options...
Mackpro Posted 6 hours ago Share Posted 6 hours ago Is it a MR or a MRU ? Find the air line going to the fan clutch and put air directly to the clutch and see if it unlocks . There should be an air solinoid that controls the air to the fan. If it’s a MR fuse 41 supply’s 12 volts to this solinoid. This fuse in in the fuse box that’s outside of the cab. Also the green high pressure switch for the AC could be bad or unplugged causing the ECM to turn on the fan . Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-568142 Share on other sites More sharing options...
mcratchet1 Posted 5 hours ago Author Share Posted 5 hours ago Sorry it is an mr688s it’s off in the morning for just a few mins then stays engaged the rest of day until just idling at shop but temp never goes over 180 if I remember correctly it only engages when temp hits 200 Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-568145 Share on other sites More sharing options...
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