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Trouble with my AC

The A/C is not working in my 2002 S-10. Currently the compressor runs, but the air is not getting cool. I tried adding freon, but it has not helped.
The low side pressure is about 50 psi, and would drop a few pounds when the compressor is started, but it drops no further. I have not noticed the compressor cycling while it is on. The can of refrigerant is not empty, but the system does not seem to be taking any more from that can.

Do I just need to add some more coolant from a fresh can, or is something else at work here.

Also, probably unrelated, when down shifting it is fairly common for the air to switch from blowing up front to blowing on the defrost.

Any help would be appreciated.

When you have an A/C system that is low on refrigerant, air has been introduced to the system. Doesn’t belong there. You need have the A/C system serviced by a professional. Have them reclaim, evac, charge, add dye to your system. That way when it comes time to do this again there will be evidence and you will have your best charge. I find it impossible to get a R-134a system cold once air has been introduced. I suppose you could try another can of refrigerant and see what happens. When your A/C is not running I would expect to see a bit higher pressure than 50 PSI. Probably something more like 80 to 100 PSI. Your blend door problem is most likely going to be a rotten vacuum hose.

You need to use a full set of gauges, a low side gauge is not enough. from your description, it sounds like you need a new compressor, but it will take a high side gauge to determine that.

If you’re at 50psi WITH the compressor running that is too high.

If you’re at 50psi without the compressor running that is too low.

No matter, really. What pete peters said about having a trained tech with the right equipment service it is correct. Sometimes you can get some more cooling out of the DIY cans - but its basically money down the tubes as its going to leak back down again.

Have a pro look at it before you hurt yourself…You need to KNOW what that high-side is doing…

How do you know the compressor runs? It may be a bad clutch. Any bad smells happening? As the compressor starts it may spin but the clutch could be fouled. Once the torque gets high enough it may slip. This would need to be torn down so a shop gets involved even if you just have them recover the refridgerant while you replace parts. A good diagnosis is in your future, or a new sweat lodge.

You need to look at the vent system before worring about the AC system.

If the vent mode changes when down shifting where the engine pulls a higher vacuum, and the mode goes from dash to defrost there’s a problem with the vent system. So the AC itself may be working properly, but there’s a problem with vent system where the blend door isn’t allowing the cold air into the passenger cabin.