shilohwestphal Posted August 18, 2022 Share Posted August 18, 2022 The AC has been working fine till this week. Looking over past post, this has been an issue with other trucks but I did not see any of the fixes. Pressures check fine. Checked both pressure switches, both check good. There is power going to the high pressure side. But the low pressure switch does not have power going to it. And there is no power going to the ac compressor clutch. So looks to me that is the problem. I have checked all the fuses but do not know which fuse feeds this circuit. Would anyone have any ac circuit wiring schematics for this model? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted August 18, 2022 Share Posted August 18, 2022 is it freezing up because it is not draining the condensation, and then the thermostat in the evap. core is shutting it down? also, are any of the control knobs sloppy, or worn out? jojo Quote Link to comment Share on other sites More sharing options...
shilohwestphal Posted August 18, 2022 Author Share Posted August 18, 2022 The problem is there is not any power going to the compressor. But one reason I have found is the low pressure switch does not have power going to it either. The switch checks good. But in the contols, this switch need to be seen in the correct state before the compressor is powered. I need a wire schematic to see how things are wired. Is it direct wired? or does it run back through a module or relay or something else. And the high pressure switch is working correctly too. I does have power. And when it is in the open state, the big radiator fan comes on. Quote Link to comment Share on other sites More sharing options...
br549 Posted August 18, 2022 Share Posted August 18, 2022 If I remember right there is a big 40 amp fuse along the bottom of fuse panel that is marked on the panel or wire going to it heater/ac. I dont think it would be bad or the fan would not work. Does the push button for a/c light up, Also it should work if you put the lever to defrost it should kick the a/c on. It goes from the control to the thermostat , you have to pull the front cover off and you will see if it has power to it and power leaving it, if not it is bad. On the ones I seen there is a in line fuse in the wire that goes from the thermostat that goes to low, high pressure switch, follow the wire on the thermostat wire and look for the in line fuse in the a/c heater box. 1 Quote Link to comment Share on other sites More sharing options...
dirtlion Posted July 26 Share Posted July 26 Same issue in my 04 CV713. Was there a resolve to this? Quote Link to comment Share on other sites More sharing options...
dirtlion Posted July 27 Share Posted July 27 So far, I know I need a new AC compressor assembly because clutch didn’t engage when I jumped the clutch terminals with a fresh 12v supply and ground. But another problem is I’m not getting a 12v supply through the connector in front of the AC clutch. This is when the AC button in the cab is on and lit up. I’ve pulled the 40amp circuit breaker in the interior fuse panel and it tests good. Fan/blower is working fine just get hot air. Tomorrow I’m pulling the AC controls from the dash and testing them to make sure it is doing its job passing the voltage. Other than the circuit breaker I haven’t found any other fuse location or relay that could be faulting and not passing current through to the clutch. Also, no obvious sign of a cut or damaged wire but I haven’t traced it all the way back into the cab just yet. Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted July 27 Share Posted July 27 (edited) did you check the binary switch and wires in the reciever dryer? Edited July 27 by Joey Mack Pour sperring Quote Link to comment Share on other sites More sharing options...
Geoff Weeks Posted July 27 Share Posted July 27 9 hours ago, dirtlion said: So far, I know I need a new AC compressor assembly because clutch didn’t engage when I jumped the clutch terminals with a fresh 12v supply and ground. But another problem is I’m not getting a 12v supply through the connector in front of the AC clutch. This is when the AC button in the cab is on and lit up. I’ve pulled the 40amp circuit breaker in the interior fuse panel and it tests good. Fan/blower is working fine just get hot air. Tomorrow I’m pulling the AC controls from the dash and testing them to make sure it is doing its job passing the voltage. Other than the circuit breaker I haven’t found any other fuse location or relay that could be faulting and not passing current through to the clutch. Also, no obvious sign of a cut or damaged wire but I haven’t traced it all the way back into the cab just yet. Do you know for sure it hasn't leaked it charge? Bad clutch/clutch coil is a sign the clutch overheated. If it doesn't lock up with 12 volts to the clutch, I would suspect other problems as well. Some coils have a "thermal fuse" buried deep in the windings. If the clutch gets too hot from slipping, it lets go and keeps the belt from snapping. No way to replace/repair the fuse, you have to replace the whole clutch. If the system doesn't have a full charge there is a safety system Often a switch on the receiver that doesn't allow power to the clutch (as JJ mentioned). So, new compressor, which will require evacuating the system, and a recharge, then see if you have further problems. It may just be a loss of refrigerant. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted July 27 Share Posted July 27 With key on , AC switch on and blower motor on at least low speed, you should have 12 volts to at least one side of the connector on high/low switch that’s screwed on the receiver drier. If the system is full of R134a then you should have 12 volts going through the high/low switch to the compressor clutch. If no voltage , pull the cover off of the AC/ heater unit . Starting sometime around 2003-2004 Mack started putting a in line fuse below the control panel. What was happening is the AC compressor clutch was shorting out and it would fry the micro switch on the control panel. With the add on in line fuse , the fuse would blow and save the control panel. Hopefully yours has the in line fuse. 1 Quote Link to comment Share on other sites More sharing options...
dirtlion Posted July 27 Share Posted July 27 The AC dryer does have 12v going to the sensor connector. Validated that yesterday as well. When the connector for the dryer sensor is disconnected the radiator fan engages high speed. I will try to find an inline fuse. I followed the wire back over the top of the engine until it drops out of sight behind the motor. I didn't crawl under the truck to continue following it yet. The wire didn't have any damage to that point at least. I have not checked the charge yet, just spent a little time yesterday with the volt meter checking electrical signals to start the diagnosis. I bought my truck from an auction and knew I would have problems given the price I paid. I'm assuming the AC clutch should at least attempt engagement when 12v is applied but makes no noticeable attempt at engaging. The truck has a salvage title but does not show signs of being wrecked. The electrical issues seem to be the main problem so far. Trailer ABS Relay in the engine bay is blown open exposing the copper coil on the inside of it. I have new relays arriving today. There was another ABS fuse on the inside panel missing I've tested all the other fuses and circuit breakers and have found none of them to be blown which is a good sign. The fuse I added to the missing ABS terminal also did not blow so that may have been a previous, rob peter pay paul situation. All of the spare fuse port locations were empty... Brake lights and blinkers also are out. When lights are on in the truck and the left signal is engaged, the left light tail light turns off while right tail light stays engaged. Nothing happens on the front flasher. Same think happens for the right flasher.. Right tail light turns off and left stays on. Quote Link to comment Share on other sites More sharing options...
dirtlion Posted July 27 Share Posted July 27 2 hours ago, Joey Mack said: did you cech the binary switch and wires in the reciever dryer? Im not sure where the binary switch is to check this. If you let me know where that is, I definitely will. I'm going to check the charge today and if it is empty, I'll start leak testing to see what else may need to be replaced. Quote Link to comment Share on other sites More sharing options...
dirtlion Posted July 27 Share Posted July 27 3 minutes ago, dirtlion said: Im not sure where the binary switch is to check this. If you let me know where that is, I definitely will. I'm going to check the charge today and if it is empty, I'll start leak testing to see what else may need to be replaced. After googling. I did check this not knowing the name of it. It also was showing 12v at the connector and also caused the fan to kick into high speed when the connector was disconnected. Quote Link to comment Share on other sites More sharing options...
Mackpro Posted July 27 Share Posted July 27 The green switch on the AC line by the drier is for the engine fan clutch only. The high/low pressure switch for the AC system/compressor clutch is on the drier itself. However if you have the factory option add on APADS system disregard the switch set up Quote Link to comment Share on other sites More sharing options...
dirtlion Posted July 27 Share Posted July 27 Well I found the inline fuse and it is not blown. I also made a new discovery. Vise grips holding the heat damper closed instead of it being connected by the thermostat push rod behind the cup holders. Quote Link to comment Share on other sites More sharing options...
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