1999 Chevy Suburban No cold air

Hello

I am not sure - but are you using test gauges...A high and low pressure manifold AC gauge set?

If not you are not going to be able to get a good reading on what the system is really doing.

Based off what you are saying, you won't get any cold air. You can begin testing with only 45 psi. You won't get any cold air, but you should start to see some compressor engagement. As soon as the compressor engages, it will cycle off rather quickly when the suction side of the compressor draws the pressure on the low side below 20 psi. You will see the low side gauge at 45 psi drop quickly to 20 psi, at which point the compressor will cycle off. Then the low side gauge will climb back up to 45 psi as the high and low side equalize. At this point the compressor will kick back on and he cycle will repeat itself. This is called short cycling. This rapid cycling of the compressor is a good indication that the system is low of refrigerant.

So a rough idea is on a 70 degree day, the low side should be about 35-40 psi and the high side about 145-160 psi. On a 85 degree day the L should be about 45-55 psi and the H about 225-250 psi.

If you don't have both gauges you will not be able to tell if something is not functioning correctly.

I suggest you call around and see what it costs for a place to check out your system to tell you if something is bad and what is bad. Many places are free for the check. Some places charge very little.

It sounds like to me the AC system is not working correctly which may be the compressor or something else.

Also your cooling fans on the car. If they are not operating when you turn the AC on, then that will cause back pressure and the AC will not blow cold air.

Please let us know if what the final fix was for your car so we can better assist others. Thanks!