mcratchet1 Posted January 30 Share Posted January 30 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 January 30 Share Posted January 30 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 January 30 Author Share Posted January 30 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...
mcratchet1 Posted February 12 Author Share Posted February 12 Ok finally checked it out blowing air does dis engage clutch. I have air going into that air switch but no air coming out. I have power but no ground. When I add a ground everything works. Checked wire to harness I do not see any issues. Does anyone know where the ground comes from? Also does that air switch disengage with ground or power? I also added a video does it look like clutch has to much wobble? IMG_8323.mov Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-569161 Share on other sites More sharing options...
Joey Mack Posted February 12 Share Posted February 12 Power on, releases the fan. When you shut the engine off does the fan spin and then lock after 7 seconds when it powers off ? Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-569162 Share on other sites More sharing options...
mcratchet1 Posted February 13 Author Share Posted February 13 Ok finally checked it out blowing air does dis engage clutch. I have air going into that air switch but no air coming out. I have power but no ground. When I add a ground everything works. Checked wire to harness I do not see any issues. Does anyone know where the ground comes from? Also does that air switch disengage with ground or power? I also added a video does it look like clutch has to much wobble? IMG_8323.mov No when I shut off key fan stop almost immediately. That’s with clutch disengage. Also when I unplugged ac line switch the clutch engaged. The truck is cold so it should not engage. Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-569260 Share on other sites More sharing options...
Joey Mack Posted February 13 Share Posted February 13 I beleive the ground is made in the EECU. Is the fans clutch broken? It look like it wobbles a bit... Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-569264 Share on other sites More sharing options...
mcratchet1 Posted February 13 Author Share Posted February 13 No it’s not broke but yes seems to wobble when clutch is engaged. The problem I’m having is it stays engaged 75% of the time. As soon as I leave in the morning Quote Link to comment https://www.bigmacktrucks.com/topic/75098-clutch-fan-problem/#findComment-569282 Share on other sites More sharing options...
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