A/C blowing warm

[04MCS]

Having issues with my '07 Tahoe's A/C system. Background. Last October it started to not blow as cold, but right about that time the tranny gave up the ghost after 220k miles. It's taken me about this long to get it pulled out, rebuilt , and stabbed back in. Last week while breaking the tanny in, I noticed it was real warm and the light on the button would do the 3 blinks and out. I bought one of the freon charge kits with the gauge. Plugged it in and it was low as expected. So I gave it a couple squirts until it had enough freon to have the compressor kick on. The compressor would start doing the cycling thing and I added freon until it was in the correct range. The A/C light will stay on, the compressor will cycle on and off, and I watch the pressure cycle up and down as the compressor cycles. Everything seems correct, except the it's still blowing warm air. I'm concerned because it seemed to go from not enough pressure to "full" with barely anything out of the recharge can, where as my Mini took almost the whole can and it still worked ok before I started. Could something be clogged that is making it read "normal" pressure on the low pressure side but still not be full? Orifice tube maybe? Any other things to check? The wife isn't enjoying the old school feel of windows down in the summer. Thanks in advance.

Tom

 

[sumo]

Our trucks take about 3 lbs of freon to fully charge. It sounds like it's still not fully charged.

 

[retiredsparky]

Did you charge with liquid or gas freon? What pressures are you seeing on suction and discharge? Could you be pushing heated air through because the heater is engaged? If the system truly needed freon, there is a leak that needs to be found or you will continue to have problems.

 

[04MCS]

I definitely don't have any of the settings set up for heat, but I guess it's possible one of the actuators is maybe holding something open allowing hot air in? A little update, the truck sat for this past week and when I started it back up, the button is giving me the 3 flashes again, so I'm guessing the pressure is low. Sounds like I'll need to get a real gauge setup, as I was just using the gauge that came with freon refill kit so it on'y attaches to the low pressure/fill side. It's weird that last week when I first messed with it, it went from no pressure to ~35 psi with very little freon added, but it would do the cycle when the compressor would kick on I don't want to just start replacing parts until I find the culprit. As for type of freon, I'm guessing liquid as the recharge cans have the "oil" in them. WHile I've build engines before, I've never messed with A/C systems so I'm way behind on this stuff.

 

[04MCS]

Also to put in context, I bought this truck new back in '06 right after this style came out and I had never recharged the A/C system before the tranny went last year, so almost 10 years and 220k miles, most of it living in the south. It was probably due a recharge.