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I have a 05 Mack vision with a 380 aset. My fan is on constantly does not want to turn off. Runs from start and does not shut off after a while like it used to. I checked it out with a diagnostic tool and no trouble codes. Also I've read on a forum to check if it moves freely without moving the belt or any pullies and it doesn't. It moves freely. Also I have disconnected the connection to it and it still on. Any advise? Thanks in advance.

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too new for my help! but I guess I'm not following you when you say you unhook it and it still runs, but spins free with the engine off.  So did it spin free in both directions? ..... with it unplugged? .....im thinking that they may have finally got smart and made a clutch that is spring applied and air released  now depending on how it could be wired it could be released with the key off if the truck still had air pressure.  

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too new for my help! but I guess I'm not following you when you say you unhook it and it still runs, but spins free with the engine off.  So did it spin free in both directions? ..... with it unplugged? .....im thinking that they may have finally got smart and made a clutch that is spring applied and air released  now depending on how it could be wired it could be released with the key off if the truck still had air pressure.  

Read on a forum check to see if the fan clutch Isnot locked up by turning the fan with your hand when the engine is off. If it's tight turn where your turning the belts also I'll need to change clutch. If it turns freely I'm good. When the engine is running I've disconnected it and still stays on. This one don't have a air line to it. It's electrical

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High pressure A/C system switch may be bad.  It could give a signal keeping the engine fan on.  Also, corrosion on the electric plug pins can cause issues.

Thank you. I'll get it checked out. Appreciate it

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If its the Behr fan, here is the troubleshooting for it.  If on this fan, if it ever locks solid its bad. Also it will never totally freewheel like an air fan clutch. In the bulletin it shows where to put 12 volts and ground to the fan to make it disengage. remember it might take 10 or more minutes to disengage and even longer in cold weather.  Also when you run your defroster in cold weather, your AC compressor is engaged. If you have high AC head pressure it could be turning the fan on. 

sb215024 ASET Behr fan.pdf

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If its the Behr fan, here is the troubleshooting for it.  If on this fan, if it ever locks solid its bad. Also it will never totally freewheel like an air fan clutch. In the bulletin it shows where to put 12 volts and ground to the fan to make it disengage. remember it might take 10 or more minutes to disengage and even longer in cold weather.  Also when you run your defroster in cold weather, your AC compressor is engaged. If you have high AC head pressure it could be turning the fan on. 

sb215024 ASET Behr fan.pdf

Thanks Mack pro. This is going to help a lot. Appreciate it. God bless

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