KevenH

I took a look. No APADS, there is an airline to the fan clutch so it must be 2 speed I would think. I fired up the AC quick just to see what it would do, now its working fine compressor is cycling as it should. My bet is on the controller.

Could be wrong but I don't recall seeing an airline to the fan. I might take a look tomorrow and I'll let you know. Thanks for the quick replies.

I'll put my hand in there and get back to ya lol. I might pop over there and take a look for APADS and the fan setup tomorrow. I'll let you guys know what I see.

I dont believe it was green, I believe it was red or brown. It sits on the high pressure line going to the drier. This is an AI427 vocational town truck I doubt it has an electronic fan.

You would know more than most of us, how does the fan work on these units? Is it a variable speed deal? How is it engaged? Im only familiar with the air setups.

Its possible the fan is a 2 speed deal it definitely spins just doesnt make much noise, after pulling a hill and the coolant temp over 190 ish is the only time I've heard the fan come on in these trucks. Im used to the single speed air fans which you can hear come on and off. These macks have a viscous fan clutch or something like that which I'm not familiar with. Im not sure this has APADS as I just read on another thread that if the high pressure fan switch is present then it is not optioned with APADS.

I just saw a picture online of it. Im not sure if it does or not I would have to look Monday. Was that a standard thing on these trucks or just an option? Says cycle the ignition 4 times on the back of it from the photo online. There's no codes on the dash.

On these older Macks there isn't any transducers, all you have is normally open or closed switches. There's a binary high and low pressure switch on the drier. It cuts out the compressor. It goes open below a certain psi and above a certain psi. If the switch is open the compressor won't run. There's a high pressure fan switch by the condensor, how that interacts in this system I'm not totally sure. When the compressor is running high pressure stays at a steady 185 depending on ambient temps. The other CV Mack we have similar vintage 2003 runs the same way. Essentially if you're inside of the range on the binary the compressor will run until the evaporator gets cold enough to trigger the freeze switch which opens cutting out the compressor. Once the evap thaws the freeze switch goes back closed and the compressor runs again. The other Mack also doesnt run the fan at all with the AC on stationary. I'm thinking the controller because of how goofy it has started to act. When I did all the work the compressor would cycle normally and everything was working fine. Then after running it for a couple weeks it started doing this.

When it was cut out I pulled the probe right out and the compressor still wouldn't cut back in. You're talking about the HVAC controller as in the unit with the blower switch? Does that talk to any other modules? I was see something about a fan module APADS is what its called I believe, that communicates with the ECM.

Yea it was doing it in the shop. When it cut out I unplugged the binary switch (high low pressure on the drier) and jumped the terminals, compressor didnt come on so it's not that preventing the compressor from running. I forgot to mention I did replace the terminals in the plug when I replaced the TXV and drier because it wasnt making good connection. The two conditions I saw yesterday in the shop were that it either cuts out and won't run the compressor with no voltage being supplied from whatever module sends voltage or the compressor runs for a good while, air out the vents is real cold then the freeze switch finally kicks the compressor out, however then it won't reengage the compressor. If you turn the truck off for a bit and run it again it tends to do the latter. Thanks.

Hello all, I have a 2006 Mack CV713 Granite. Initially the A/C didn't work. A compressor was put on it before I got to it but the TXV and drier were not replaced. I replaced the TXV and drier, vacuumed, added oil and charged it up pressures are 20 on the low and 175-185 on the high side at 80 degrees ambient. It was working good and cycling properly for a few weeks. Now it kind of does what it wants sometimes theres no voltage to the compressor or the freeze switch wont kick out the compressor. I took the panel off the evap, the evaporator and the compressor suction line were iced up. I moved the freeze switch probe a little and it hasnt done that since. Binary switch is fine, freeze switch tests fine. With a power probe I test at the freeze switch and when it acts up there's no power supplied to it nor the 15 amp fuse next to the HVAC controls When the compressor is running I jave voltage there. When the a/c is cold and the freeze switch kicks out the compressor I have voltage on one side none on the other which is normal operation. When it does kick out the compressor some of the time the compressor won't reengage unless you shut the truck off and wait a little while. So whatever module controls the AC system seems to be doing erratic things. A wiring diagram would be helpful to trace the power path for the A/C compressor. Im also thinking maybe a fan issue as the fan rarely comes on when the a/c is running stationary, fan only comes on when coolant temp gets up to 190-200.