AC has freon (134a) pressure is good. Compressor

its not 1 number. sorry !
its a table.
its in the SUZUKI FSM. "factory service manual"
here is one for trackers. chebby.
do not overcharge 134
http://www.fixkick.com/AirCond/r134-1996-chart1w.jpg

Only a qualified mechanic can do this. Special tools and gauges are required.

The refrigerant (it's not freon) needs to be at a specific level. If there's too much, or not enough, it will not get cold.

Some things to look for:
Compressor cycling. The compressor turning on and off repeatedly in, relatively, short time periods; typically within 20 seconds. If it is doing this, it is most likely low on refrigerant. If it does it very rapidly, it could mean that there's too much.

Make sure that the temperature selector on the climate control system changes air temperature. If it does not, there may be an issue within the air mode mix motor, or the blend door.

that depends on what happened to the last one.
if the last one , broke up inside it then contaminates the whole system, insuring the new compressors early death.
at the least, a compressor, receiver /dryer. (my be the expansion valve)
1: must be done in a shop, so they can capture the old freon.
ie: Ozone damage, ever heard of that?
2: then replace all bad parts.
3: next, pull a hard vacuum on the system (removes all water)
4: adds freon by weight.
5: test system for full performance and correct any deficiences.

by that can, with hose. and gauge.
see connnector on hose of can. see it?
now on car there are 2 pipes, and one has large conn, and one is small
only 1 fits hose. easy huh? us the one that fits.
do not run the compression if there is no A/C, you can burn it up.
the Freon has PAG oil that must he present , if missing BOOM.
BIG MONEY!

it is low you need 1 can of 134a freon you can pick up at any auto zone or advance auto so on check with the counter person to make sure you have the right one good luck

Go to wal mart $6.00 a 12 oz can,may need 2 cans. Car owners manual will tell capacity in oz of AC system never charge over that amount into your system, also PSI and ounces are not the same thing

Go to auto parts store buy R-134a charging hose kit with a gage built in.$ 10.00

Turn engine OFF Under the engine hood, is a large aluminum cannister usually on passengers side ,on it or on a hose coming out of it will be a black plastic cap,with a connect fitting under, remove cap, pull and hold back the locking ring on the charging connector and push on fitting. look at gage it will show how much freon pressure is in system, with engine and ac off a higher pressure value will be on gage Start engine and turn ac on cooldest and fan high. The pressure will drop. if the pressure drops below about 22 PSI the ac compressor will stop automatic by the low pressure cut out switch.then the pressure will build above 25 and the compressor will engage again, this is short cycling(no/off) on the low pressure sensor and is a good indicator of a low charge of refigerant(R-134a). Charge according to instructions on kit. When the pressure stays above 28 and the compressor stops cycling off your good DO NOT over charge or you can cause compressor slugging. Liquid into compressor($1200.00 for new compressor)
SAFETY!!!!
R-134a can cause blindness. wear goggles and gloves

The "O" ring seals in the ac system dry out when the ac is not in use for over a month and leak the refigerant out again, So Use your defrost setting in the winter because it runs the ac compressor for dehumidifying, but only after the engine has warmed up a little, or with no warmth from engine the defrost will blow freezing air.

Patrick Mot

This is most likely the cycling of the AC unit. As the compressor pressurizes the 134a Freon you get the cold air, once it reaches a certain pressure it cuts out. If you are low on Freon it will cycle out more often. Check your freon level with a gauge to see if your within the proper tolerance. If the compressor runs for a period and doesn't reach the right pressure it will cut out to keep from damaging your compressor so it is important to keep the correct amount of freon in the system.

The power to run the compressor clutch coil goes from the battery, to the AC Clutch Relay, somewere in the engine compartment fuse box, then it goes to the positive side of the AC compressor clutch coil; goes thru the coil, activating the compressor, and then goes to complete the circuit through another switch (high pressure protection switch) in the back of the AC compressor and finally reaching negative or Ground.

Disconnect the AC compressor clutch connector and using a 12 V bulb with 2 wires (test lamp) check the following:

1.- connect 1 lamp wire to battery neg; with the other check both pins at connector with the AC in the RUN (AC and ignition switch on ) you should have power in one side.

2.- connect 1 lamp wire to battery positive and with the other check both pins at connector, lamp should light getting the ground from the clutch connector thru the high pressure compressor switch to ground.

On the other side what makes the relay close and let the power flow to the clutch works with the low pressure switch, (if the freon pressure is too low it opens and kills the ground to the relay coil and that kills the compressor), that low pressure switch is in the low pressure side of the freon tubing, the fat pipe that comes from inside the firewall into the accumulator/dryer, a big aluminum cylinder sitting on the right side of the engine compartment in GM cars.

To know if the low press switch is the cause you can unplug it and connect both legs with a paper clip for a minute or two, no more, you don't want to damage the compressor. anyway if jumping the switch makes the compressor come alive and kick in, you either have low freon pressure or a bad switch; it's time for the pressure gauges and check how the compressor is pumping and that is better left to a pro.

By the way you said that your system is a R-12 system, have you considered switching to R-134a the new "ozone friendly" freon? to do that you need to evacuate the system with a recycling machine and pull vacuum in your AC, if it holds the vacuum for a while, then you can be sure that there are not leaks and then dump 1.5 or 2 pound (check the labels in the engine compartment) of R-134a into your system. it will be a good idea to put some fluorescent leak detecting dye in the system to check for leaks, just in case..

if your low on freon the unit will not work.low pressure switch cuts it off. or you have a bad a/c clutch asy.