KevenH Posted yesterday at 03:04 AM Share Posted yesterday at 03:04 AM 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/ Share on other sites More sharing options...
Joey Mack Posted yesterday at 09:41 AM Share Posted yesterday at 09:41 AM You say the binary switch is good ? Can you duplicate the issue in the shop ? The system needs at least 50 psi to start the compressor, any chance the terminals in the wire at the binary switch are loose or rotted away ? Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579363 Share on other sites More sharing options...
KevenH Posted yesterday at 10:08 AM Author Share Posted yesterday at 10:08 AM 21 minutes ago, Joey Mack said: You say the binary switch is good ? Can you duplicate the issue in the shop ? The system needs at least 50 psi to start the compressor, any chance the terminals in the wire at the binary switch are loose or rotted away ? 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579364 Share on other sites More sharing options...
Joey Mack Posted yesterday at 10:30 AM Share Posted yesterday at 10:30 AM can you remove the probe from the core and let it hang in the open and re-test. I do know however, that the control panel is kinda junky. I have replaced them many times for similar issues. I hate loading parts into the cannon, but sometimes I do it. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579365 Share on other sites More sharing options...
Geoff Weeks Posted 23 hours ago Share Posted 23 hours ago Not knowing the Mack system I will make some comments on what you observed. Condenser fans not running: This is a clue, when stationary something has to move air over the condenser. What is the high side doing while the compressor is running and the truck not moving? fans should kick on around 325 psi or so. 2nd some new stuff (and don't know if this applies here) don't use pressure switches but instead use pressure transducers which send a variable pressure signal to the controller. Jumping these can cause problems, but most often they have 3 terminals on them, and IIRC yours have 2. In my experience it is extremely rare for a Tx valve to be a problem. So I see two possibilities. 1: the fans aren't coming on and a safety is locking out the compressor and doesn't reset until the truck is shut off and re started. This would imply some sort of high pressure cut-out in the system, either transducer or a HPCO switch. Again I don't know the Mack system for this year 2: more likely, Control panel, if it is responsible for turning on the fans, and turning off the compressor when the frost switch tells it the temp has reached freezing. Hits both problems if the control panel is where these outputs come from. May be someone else can chime in, does the controller receive the inputs from the frost and binary and then control the fans and compressor (either directly or through relays)? Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579372 Share on other sites More sharing options...
KevenH Posted 11 hours ago Author Share Posted 11 hours ago 13 hours ago, Joey Mack said: can you remove the probe from the core and let it hang in the open and re-test. I do know however, that the control panel is kinda junky. I have replaced them many times for similar issues. I hate loading parts into the cannon, but sometimes I do it. 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579424 Share on other sites More sharing options...
Joey Mack Posted 11 hours ago Share Posted 11 hours ago Does it have an APADS controller mounted on the left side around the coolant tanks. ?? If so there should be faults indicated on it. Do you know how to clear the APADS out ? Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579426 Share on other sites More sharing options...
KevenH Posted 11 hours ago Author Share Posted 11 hours ago 12 hours ago, Geoff Weeks said: Not knowing the Mack system I will make some comments on what you observed. Condenser fans not running: This is a clue, when stationary something has to move air over the condenser. What is the high side doing while the compressor is running and the truck not moving? fans should kick on around 325 psi or so. 2nd some new stuff (and don't know if this applies here) don't use pressure switches but instead use pressure transducers which send a variable pressure signal to the controller. Jumping these can cause problems, but most often they have 3 terminals on them, and IIRC yours have 2. In my experience it is extremely rare for a Tx valve to be a problem. So I see two possibilities. 1: the fans aren't coming on and a safety is locking out the compressor and doesn't reset until the truck is shut off and re started. This would imply some sort of high pressure cut-out in the system, either transducer or a HPCO switch. Again I don't know the Mack system for this year 2: more likely, Control panel, if it is responsible for turning on the fans, and turning off the compressor when the frost switch tells it the temp has reached freezing. Hits both problems if the control panel is where these outputs come from. May be someone else can chime in, does the controller receive the inputs from the frost and binary and then control the fans and compressor (either directly or through relays)? 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579429 Share on other sites More sharing options...
KevenH Posted 11 hours ago Author Share Posted 11 hours ago 8 minutes ago, Joey Mack said: Does it have an APADS controller mounted on the left side around the coolant tanks. ?? If so there should be faults indicated on it. Do you know how to clear the APADS out ? 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579431 Share on other sites More sharing options...
Geoff Weeks Posted 10 hours ago Share Posted 10 hours ago There HAS to be air flow over the condenser, so either there is a two speed fan drive, or some other way, to get air flow. It does sound like a typical older system and possibly APADs. I was trying not to mislead so was somewhat vague, but also point you at places to look. A A/C cannot function without air flow over the condenser, period. Without air flow, no heat can move. So either there is some fan operation or there is a HPCO that turns off the compressor, otherwise the pressure will build on the high side until a relief opens or a hose pops. The fact that you say there is no fan when idling, and that the compressor sometimes shuts down and will not re start points to a high pressure problem. I'm leaning toward an APAD's system/ problem. For the high side not to rise while stationary say there HAS to be air flow over the condenser. Switch on the receiver can be either a single (low pressure cut out) or binary (low and high pressure cut out) they look EXACTLY the same and the plug is the same, make sure it is working as it should. I know A/C work, what I don't know is exactly how the system was made on your truck. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579432 Share on other sites More sharing options...
Joey Mack Posted 10 hours ago Share Posted 10 hours ago Yes to a binary switch on the receiver dryer, no to standard APADS install. Yes to air flow. Yes to high pressure shutting it down. Yes to possible control unit failure.. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579433 Share on other sites More sharing options...
KevenH Posted 10 hours ago Author Share Posted 10 hours ago 4 minutes ago, Geoff Weeks said: There HAS to be air flow over the condenser, so either there is a two speed fan drive, or some other way, to get air flow. It does sound like a typical older system and possibly APADs. I was trying not to mislead so was somewhat vague, but also point you at places to look. A A/C cannot function without air flow over the condenser, period. Without air flow, no heat can move. So either there is some fan operation or there is a HPCO that turns off the compressor, otherwise the pressure will build on the high side until a relief opens or a hose pops. The fact that you say there is no fan when idling, and that the compressor sometimes shuts down and will not re start points to a high pressure problem. I'm leaning toward an APAD's system/ problem. For the high side not to rise while stationary say there HAS to be air flow over the condenser. Switch on the receiver can be either a single (low pressure cut out) or binary (low and high pressure cut out) they look EXACTLY the same and the plug is the same, make sure it is working as it should. I know A/C work, what I don't know is exactly how the system was made on your truck. 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579434 Share on other sites More sharing options...
KevenH Posted 10 hours ago Author Share Posted 10 hours ago 4 minutes ago, Joey Mack said: Yes to a binary switch on the receiver dryer, no to standard APADS install. Yes to air flow. Yes to high pressure shutting it down. Yes to possible control unit failure.. 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579435 Share on other sites More sharing options...
Joey Mack Posted 10 hours ago Share Posted 10 hours ago If your fan has the wires inside a thick black hose at the fan then you have a smart fan. So yes to multi speeds. Im getting rusty. Been away for 4 years now. Also, if you have the green pressure switch in the A/C line, then that is the fan signal switch.. My rusty ass may be on a roll here..🍻 Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579436 Share on other sites More sharing options...
KevenH Posted 10 hours ago Author Share Posted 10 hours ago 1 minute ago, Joey Mack said: If your fan has the wires inside a thick black hose at the fan then you have a smart fan. So yes to multi speeds. Im getting rusty. Been away for 4 years now. Also, if you have the green pressure switch in the A/C line, then that is the fan signal switch.. My rusty ass may be on a roll here..🍻 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. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579439 Share on other sites More sharing options...
Joey Mack Posted 10 hours ago Share Posted 10 hours ago Same same. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579440 Share on other sites More sharing options...
Geoff Weeks Posted 10 hours ago Share Posted 10 hours ago A single speed air fan drive, will either be stopped at idle or turning very slowly by the drag in the bearings. A two speed will be turning faster. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579441 Share on other sites More sharing options...
Joey Mack Posted 10 hours ago Share Posted 10 hours ago Is the fan a Horton air controlled type ? Can you see the clutch assembly through the sides of the fan clutch ? Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579442 Share on other sites More sharing options...
KevenH Posted 10 hours ago Author Share Posted 10 hours ago 3 minutes ago, Geoff Weeks said: A single speed air fan drive, will either be stopped at idle or turning very slowly by the drag in the bearings. A two speed will be turning faster. 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. 1 Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579443 Share on other sites More sharing options...
KevenH Posted 10 hours ago Author Share Posted 10 hours ago 5 minutes ago, Joey Mack said: Is the fan a Horton air controlled type ? Can you see the clutch assembly through the sides of the fan clutch ? 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. Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579444 Share on other sites More sharing options...
Joey Mack Posted 10 hours ago Share Posted 10 hours ago Post some pics. I doubt it has APADS.. It may just be a viscous fan.... No sweat, i enjoy this.. jojo Quote Link to comment https://www.bigmacktrucks.com/topic/75794-2006-mack-cv713-ac-cuts-out-erratically/#findComment-579445 Share on other sites More sharing options...
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