Cadillac My AC. was working but just stop. The small line which is the only line to charge the system is cold,the compressor is is cycling on and off,but their is no cool air comming iside the car. Is there a reset code or something why it works like that.

probably overcharged the system and now the high pressure switch is stopping the ac from working
did you fix the leak first

there's a pressure switch on the receiver/dryer tank on your system id bet , this is momentarily shutting off your compressor clutch as the receiver tank is being pulled m/t of refrigerant , this most times is an indicator of a small hole in system and some of your refrigerant charge has leaked out , a pressure gauge would confirm this

note: automotive ac systems possess high pressures that can seriously harm anyone that opens the "wrong" line
always obtain a good tech's help if your knowledge is not enough on this

the compressor will cycle on/off when the cabin temperature is reached
the larger pipe will be cold to touch as it is the suction line for the compressor
if you have a problem with the ac ,it will not work the compressor at all and the lines will not get cold
When in doubt take it to an accredited ac specialist shop and have the system check out.

there are 3 switches that control the operation of the ac compressor . There is a high pressure switch that will not allow operation if the head pressure goes too high ( excessive gas-blocked system-tx valve condenser fan not working )There is a low pressure switch that stops the compressor when the gas has leaked out and is insufficient A thermostat that will not register and so will not switch on the compressor and finally ac compressors will not work unless both the ac switch and the blower are switched on. Have the system checked out by an accredited ac specialists.;l

Hello
Based on what you have said and my 30 years a Ford dealer tech I believe you have a slightly low AC system refrigerant charge due to a small leak at the AC compressor or the AC line connections. I would have a shop hook up a set of gauges to monitor the pressures at idle and see just how low it is. DO NOT ADD UNTIL YOU KNOW HOW MUCH IS NEEDED, YOU CAN LOCK UP THE COMPRESSOR.

Look for the large ac line/hose coming out of the ac compressor,and follow that line until you come to a small ac port,this is the low side where you will hook up to to charge.I take it you have purchased a charge hose and freon?Put the can of 134a freon on the can tap at end of charge hose,and the quick connect will snap on the low side ac port on the vehicle.Turn the freon can upside down and turn the t handle on the can tap until it pierces the can.Start the vehicle,and set all settings high blower motor,max air,recirculate mode.The ac compressor should cycle on and off,this is normal,until there is enough freon in system.When the can starts to empty,shake the can lightly until empty.It will be hard to tell,but you will figure it out.Turn the can t-handle back out,and unscrew the can an repeat process until enough freon is in the system.You can get to much freon in the system.so see hoe much it takes to fill it on the label under the hood.If the system was not empty,it won`t take the fill amount,go slow,and feel the cold parts(large ac line near the firewall).They should get dern cool,to cold,and sweating really good.Stop when this happens,and it is cool inside.

on my 99 devillle concours cold air blows from left and back vents but hot air blows from right vents

You probably have leaked out your freon after so much time. Try adding some more Freon if it doesnt stay charged you may have bigger issues.

No inline filter, you may need to recharge this system if the compressor is cycling on and off with no cold air. check the lines for leaks. check the clutch on the compressor as well for its operational value. it should engage with a click during the cycle.

There are two A/C refrigerant lines. The small line is your high pressure line and the larger line is your low pressure line.
Start at the fire wall and follow the "large " low pressure line to the compressor. The low pressure charge port will be some where on that line.
DO NOT try to recharge on the high pressure side ( small line )
Good luck, let me know.
Regards,