2003 Blazer AC Problem...HELP!!

Ok...
I have a 2003 Blazer.
One day the AC is on and working fine, the next day it blows hot air.

All fuses are good.

I bought a R134a charging/testing kit and when I test it it indicates that the PSI is over 100 (the kit says that if it is that high low refrigerant is not the problem)

So i did not add any...Does anyone know what the problem might be???

Thanks in advance...
Jmat1980

I let it sit for a while and still the same problem, any thoughts?

You have to hook up on low side. When compressor off you will see 100lbs. When the compressor engages the pressure should drop to around 27lbs. For proper diagnostics you need high and low side readings. To much freon is just as bad as not enough. It take time and training to get ac systems working properly. Now for a little more info you would be suprised as to how many bad GM compressors I have seen on Blazers and full side trucks. Most of time when they turn on the gages stay about the same. This is a bad compressor with bad reed valves.

Is the compressor turning on?

Yes it is, and the AC seems to be working fine lately...