1999 GMC Suburban, Dual front and Rear A/C. Rear blows cold, Front luke warm/cool?

[4acee@sbcglobal.net]

K1500 5.7l Vortec. I checked and added a little refrigerant to the system (r134a). It is where it should be for my ambient air temperature. Has two controls one for front and 1 for the back. Back blows cold. and front is luke warm/cool. All lights work appropriately, A/c light comes on, compressor clutch engages, and max cool on temp dial, turns on the recirculation lighted button. However it seems that I remember hearing the difference in blower air out of the vents between normal cool and recirculation. I don't hear that difference anymore. Air blows out of the respective vents, like: floor, defog, panel vents, etc. when selected. It just seems that the air pressure doesn't change when max cool/ recirculation is desired.

What would be my first place to check, and possibly see if I can move a stuck door flapp, without dash disassembly?

 

[Molson02536]

K1500 5.7l Vortec. I checked and added a little refrigerant to the system (r134a). It is where it should be for my ambient air temperature. Has two controls one for front and 1 for the back. Back blows cold. and front is luke warm/cool. All lights work appropriately, A/c light comes on, compressor clutch engages, and max cool on temp dial, turns on the recirculation lighted button. However it seems that I remember hearing the difference in blower air out of the vents between normal cool and recirculation. I don't hear that difference anymore. Air blows out of the respective vents, like: floor, defog, panel vents, etc. when selected. It just seems that the air pressure doesn't change when max cool/ recirculation is desired.

What would be my first place to check, and possibly see if I can move a stuck door flapp, without dash disassembly?

Start with the simple and inspect all your vacuum lines in the engine compartment. A weak vacuum to your HVAC system cause by a crack line aill cause what your experiencing. Repairing a crack vacuum line is the easier thing to check first then taking your dash apart to check the A/C heater door actuator being stuck.

If you go to the parts counter of most any GM dealer, they can print up a picture of the vacuum line diagram out of their parts book that shows where all the lines goes, better then just someone telling you which lines are what so there is no misunderstanding. Better to do the job right the first time then to repair a mistake caused by the wrong actions.

Good luck and start with that, common for the lines in the engine by to get hard due to time and heat promoting cracking.

 

[ISLANDER914]

I had the same problem with the ac on my 99 suburban. I thought adding some refrigerant would help but I was wrong. Do your self a favor. It shouldn't be more than 125 dollars, have your system checked buy a technician. turns out that dual ac system takes like 3lbs of refrigerant. When they evacuated my system it had less than a pound and that was after I added a can of r134. They should evacuate your system, make sure it holds a vacuum (slightly negative pressure), then add the correct amount of r134, oil, and a die that they can see with a black light to again check for leeks when the system is running. That's what I had done and now my wife says its too cold. oh well... As for the recirc issue I would get going 55 set the direction to blow out the dash vents hit the recirc button and see what you get. If the light is on you should have no air flow. when the light is off the vent should be open and you should have natural air flow. Hope this helps and good luck.