AC sytem confusion

[buzzinghalfdozen24]

Problem; AC isn't blowing cold air out the passenger side air ducts.

Data: Driver side-50*, Passenger-80*, ambient temp- 85*

History: Owned truck years. Always had weak air potential from passenger side. I suspected blend doors, but never attempted repairs because I rarely haul passengers. This spring my heater core started leaking coolant rather quickly in the cab. So on went the AC repairs. I tore dash out to change heater core. I had to cut the evaporator lines because I couldn't get them to disconnect, so as a result, got a new evaporator, new heater core and new AC line to evaporator. Had bad luck changing out the accumulator/dryer, so I had to cut the line there as well. So I got new AC lines. Compressor clutch had always squeeled when disengaged, so I said screw it, I might as well do everything at once and have a perfect 100% new sytem, minus the condenser. I'm not one to short cut things, so I've known the plastic blend doors had tendencies to break. So on I disassembled the HVAC box completely and put all new Heater Treater blend doors in. Since I had HVAC box disassembled, I did not cut and tap the box, I just swapped them in the right way. Reassembled, and tested all blend door actuation with 12v battery, no issues. Charged, no issues. AC tested 40* at driver duct. Forgot about old air flow issues to passenger side, until I had people in truck for holiday weekend.

Summary: New; evaporator, all lines, compressor, blend doors, accumulator.

Any ideas folks?? I know these systems are known to be weak on passenger side, but I basically have a brand new system.

 

[Tuesdak]

Does your system have a dual zone temp option?

How did you charge the system? If the system is low the passenger side will be warmer than the driver's side. Verify if the inlet and outlet for the evaporator is near the same temp. Like 5 degrees max.

 

[PWong]

Low refrigerant.
I would recycle/evacuate/recharge with the right amount of refrigerant.

 

[buzzinghalfdozen24]

No dual zone. Technically, I guess low charge pressure makes sense. If it was low on Freon, it wouldn't have the capacity to stay cool all the way through the evaporator, correct?

Charged it at work. Nice matco unit. Pulled vacuum, let it sit for like an hour or so. Same reading, so no drop in vacuum. Added oil and charged to spec. Ran AC system and checked vents, immediately was down to 40* output. You might be right though if I had a slow leak about the whole low Freon situation.

 

[PWong]

You have superheated vapor at the upper half of evaporator when low in refrigerant.
Passenger side vent gets air from the upper half of evaporator.
Now you are low in refrigerant.

 

[buzzinghalfdozen24]

Makes sense, I'll charge/check it here soon. Rain this weekend, so it might be a good weekend to play with it.

 

[Bill Stockard]

Low refrigerant.
I would recycle/evacuate/recharge with the right amount of refrigerant.

The correct amount is by weight.

Bill

 

[buzzinghalfdozen24]

Update, pulled vacuum, held for over a half hour without dropping. Recharged to exact amount by volume. AC is much better. Not PERFECT, but much better. But coincidentally we haven't had the 90-100's like we were when I was first posting.

Thanks for the feedback, lots of good information on here.