To verify that there is a blend door type issue , you could pull off the 2 heater hoses from the heater core, buy a connector/bridge to join those 2 hoses together. I just did this and it proved to be a blend door issue. This will take the heat out of the heater core so you can get a heat-free readi...

H – too low L – too high Low refrigerant level or failing compressor With the gauges connected, rev the engine to 2000 RPM and watch what the pressures in the AC system do. Do they move closer together (high side gets lower while low side gets higher) or do they move away from each other? If they mo...

Your Low side too high and your High side is too low. Is the fan working at the condenser and is the condenser relatively clean - not clogged by debris? Yes - you pull the vacuum first and then charge.

I went and bought a cheap $20 digital scale from Harbor Freight a few days ago because I was always guessing/hoping that I had got the right amount in. The pros charge by weight scales to be 100% accurate on the charge. What happened when you tried to add more refridgerant? Did the pressures go up? ...

Would the high side coupler being messed up cause the system to not ingest Freon after taking in one 8oz can and reflect higher than normal low side psi? To answer your question, No , you don't even have to have the high side connected to the gauges when charging (although it is advised). Those coup...

You might try an internet search on the blend door on the Sierra. Common problem. With the heater by-passed for the summer, your defroster will not work. I've done lots of searching for blend door on the Sierra and the common problem that people have is for those with dual zone climate. For example...

just in case this helps anyone, I was able to achieve 43 degrees out the vents after i bypassed the heater core. its 90 degrees outside here. I'm thinking about leaving it this way for the summer

I'm not familiar with a heater core reheat. But I will bypass the core tonight to see if it improves the AC.
thanks

Howdy, As the title states I am not getting nice cold air out of the vents. I measured vent temps and they are almost 70 degrees. On a 93 Degree day here in Texas. Today I decided to evacuate the system, pull a vacuum that held , and then recharge to the correct amount of 21oz. Vent temps are still ...

Yes....

thank you