Cpitt32 Posted July 13, 2023 Share Posted July 13, 2023 Hey Guys... Just a quick question about my Mack... My AC seems to blow all sorts of cold in the front of the cab, but in the sleeper it blows warm air... Any ideas... Let me know... Thanks... Quote Link to comment Share on other sites More sharing options...
0 Geoff Weeks Posted July 14, 2023 Share Posted July 14, 2023 Ok, I'll preface this by the fact I don't know your year, but most all bunk units I see have a solenoid valve that cuts the refrigerant when the bunk system is not turned on. That would be the 1st thing I'd check. should be powered when A/C is called for my the bunk control. Bunk units I am familiar with have their own Tx valve, so that is number 2 Next look at the unit itself and see if any refrigerant is flowing in the bunk unit. Look for temp change on the liquid line before and after the Tx valve. If none, then there is no flow (likely number 1) if there is a temp drop but the outlet tube is warm, it may be low on refrigerant and the front is 'hogging" all the liquid. Quote Link to comment Share on other sites More sharing options...
0 Cpitt32 Posted July 14, 2023 Author Share Posted July 14, 2023 Thanks for the info Geoff... I appreciate it... Quote Link to comment Share on other sites More sharing options...
0 Joey Mack Posted July 14, 2023 Share Posted July 14, 2023 how long have you had this truck?? did You! ever have cold air in the bunk?? I have made these repairs a bunch of times for guys that bought trucks, and didnt know that a blocking plate was put on the bunk lines just under the firewall.. ie: Frieghtliner C-120's.. the bunk lines were blocked because the evap core under the bunk bed was junk.. anyway, Quote Link to comment Share on other sites More sharing options...
0 Cpitt32 Posted July 14, 2023 Author Share Posted July 14, 2023 (edited) 20 hours ago, Joey Mack said: how long have you had this truck?? did You! ever have cold air in the bunk?? I have made these repairs a bunch of times for guys that bought trucks, and didnt know that a blocking plate was put on the bunk lines just under the firewall.. ie: Frieghtliner C-120's.. the bunk lines were blocked because the evap core under the bunk bed was junk.. anyway, Hey Joey Mack... I bought the truck about four months ago now... Never had cold air in the bunk...I'll try and check it out... Thanks... Edited July 14, 2023 by Cpitt32 forgot something Quote Link to comment Share on other sites More sharing options...
0 Mackpro Posted July 14, 2023 Share Posted July 14, 2023 On the Mack sleeper HVAC. Coolant flows through the heater core all the time . There is a blend door that moves to block off the heater core or the AC evaporator depending on if you got the sleeper control panel on hot or cold or somewhere in between. The sleeper AC evaporator has its own expansion valve and runs off the regular AC system of the truck. The actuator sits on top of the unit and you should be able to see it move when you go from hot to cold. I have seen some northern speced trucks that only had a heater in the sleeper. 1 Quote Link to comment Share on other sites More sharing options...
0 Geoff Weeks Posted July 14, 2023 Share Posted July 14, 2023 The electric valve I was talking about was in the REFRIGERANT line not the coolant line. The Mack sleeper I have has that valve but I don't know the year. The valve is there so that if the bunk unit is off, no air flow through the cores, that no refrigerant flows so the evap core doesn't ice over. It is possible that the newer Red Dot units do it different than the older one. The system I am familiar with control the compressor based on the temp of the front evaporator. If there is less or no air flow over the bunk unit, it will cool below the frost point. You can't have a frost switch in both evaporators and have a workable system, but there does need to be a way to stop refrigerant (again, not coolant) flowing in the evaporator (again not heater core) when the bunk unit is not being used and the front system is. Quote Link to comment Share on other sites More sharing options...
0 Cpitt32 Posted July 22, 2023 Author Share Posted July 22, 2023 Alright Guys... I guess I am just a big dumb dipshit... It looks like it's just the blower fan that isn't working... It will not work on heat or AC... I've checked the fuses and relays... Not sure what I need to look at next... Let me know if you have any ideas... Think I will probably just be ordering a new blower motor and resistor... Quote Link to comment Share on other sites More sharing options...
0 Joey Mack Posted July 22, 2023 Share Posted July 22, 2023 Turn the fan switch on and check for power at the fan wires.. if there is power, and no fan operation ... Bad fan.. Quote Link to comment Share on other sites More sharing options...
0 Geoff Weeks Posted July 22, 2023 Share Posted July 22, 2023 My Marmon uses an almost identical unit to the Red Dot in my Mack sleeper. From what I remember, the thermostat control on the sleeper wall turns the fan on and off based on temp. The thermostat goes bad and fan doesn't run. As Joey suggests check for power to the fan, if there is power but no fan, then the fan is at fault, if there is no power it could be the fan resistor or the control board. Quote Link to comment Share on other sites More sharing options...
0 Mackpro Posted July 24, 2023 Share Posted July 24, 2023 Sometimes there is a sleeper fan switch on the dash or overhead console. This is where the driver can turn the sleeper blower motor on or off while driving. If it’s switched off I believe the rear controls won’t work. Quote Link to comment Share on other sites More sharing options...
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Cpitt32
Hey Guys... Just a quick question about my Mack... My AC seems to blow all sorts of cold in the front of the cab, but in the sleeper it blows warm air... Any ideas... Let me know... Thanks...
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