AC blowing hot air, after system vacuumed & it worked for 3 days.

Did you actually vacuum the system down close to 30 lbs.,and let it sit a while to check for leaks?

 

I’ve got a ‘95 FL and I have no idea if it’s the same as a ‘06, but there is no blend door in mine. It’s just a valve that cuts the water flow off. If that’s like yours that would be the first place to check.

 

If the compressor kicks on with the dash switch gear and gets cold to the touch I would say it's probably working right and you have a vent/HVAC issue. This might make sense if you switched it to defrost one time and now it's consistently blowing warm no matter what setting you select with the dash knobs. If the vent temperatures are acting inconsistent based on what time of day it is and how hot the underhood temps are I would be more inclined to say it is more likely an under/overcharge issue which would point back to the place that did the service on it. I can tell you from experience A/C issues make me cringe because they can be fussy systems to troubleshoot and fix right the first time and I've had many shops screw it up and had to bring it back.

 

Might be a little bit low on refrigerant. Pop the hood and follow the heater hoses. Shut off the valves. I heard they changed the systems quite a bit. Not sure if they switched to blend door. On my 2000, Cabs Temp valve is manually operated by a cable. Lower right corner of fuse box. Also can take off the passenger kick plate to change it. At least check the operation. Sliding the hot cold control on dash. Feel hose on both sides of the valve. Tell if it’s working or letting hot coolant leak through into the heater core. Sits right next to evaporator. Will cancel out A/C efforts. You can remove the top center panel, watch the operation of the air valves that control air direction. Also can remove the passenger front dash panel if needed. Shouldn’t have to. Everything is accessible from the top. Each valve should move using the dash position control. You’ll hear them. They usually leak air when bad. You’ll hear them. There’s 2 main valves and 2 others at each far side of cab.

 

There’s 4 pistons total. #7, #8, and 2 ea. # 29’s. They only control air direction. # 8 controls vent/heat # 29 on passenger side closes recirculating door when set on max a/c. # 7 controls heat/defrost vents. I guess # 7 could technically be considered a blend door control because it sets full heat vents, or a blend of heat/defrost vents, or full defrost. Drivers # 29 controls little useless dash vent near door. Only the water valve controls temp. Unless it was changed after 2000-2002. Maybe. I’d say if you have a manual cable operated temp valve, this diagram is accurate.Same system as my 2000.

 

This shows the manual cable for temp valve. # 9

 

Be nice to know if the bunks working or not. Fan blows on high only, means bad resistor. Located on top of the bunk heater box. Easy to change. Fan won’t blow at all, probably a bad fan. Might be the switch. You can unplug the switch and jump it, to make fan work if switch is bad. Common problem is the plug melting at the switch. Best to replace harness, switch, and fan. Supposedly the fan goes bad, still works, but draws too much juice. I don’t buy that. The problem is cheap switches. Who knows, best to check yours. It’s almost a fire hazard. New fan, keep old one for a spare. You’ll need it someday for sure. Dash and bunk fans look alike. Different plugs for a reason. They run in opposite directions and aren’t interchangeable. Pretty sure the squirrel cages are also opposite fan pitch/direction.