I bought the r-134a retrofit and recharge kit from checkers. I put on the adapters and before one can went in the pressure guage already showed in the yellow for above 40 psi. The a.c. is a little colder but should I add the rest of the cans?

I think the system takes 2 lbs. 16 oz per lb

If the system was completely empty and assuming you pulled a vacuum on the system for more than 30 minutes it will take almost all of 3 12oz refrigerent cans.

Did you just hook up the retrofit kit and start recharging? R12 and R134a are not compatible. Your best bet is to take it somewhere and have it evacuated professionally. Now here is the problem if you have mixed 134a with r12. Most AC shops do not like to evacuate a system that has been mixed. It contaminates thier R12 or R134a evac systems. But you should do all you can not to vent to the atmosphere.

If you can get it evaced at a shop, you can buy a vacuum pump @ harbor freight and pull the vaccum yourself. You need to pull a steady vaccum on the system for at least 30 minutes. The longer the better. This will also help determine if you have any serious leaks. If it will not pull and hld a vacuum then you have a leak that needs repaired before you start charging. If you can pull a vacuum and it will hold, the first can of refrigerent can be put into the system without the car running. The first can should be one with dye in it. After it is in the system, you can go around and check for leaks before you continue. Be sure to use the recommended compressor oil, PAG or Ester I believe for R134a. It sounds like a lot but it is fairly easy once you have the system evacuated. Give us some more details and we can walk you through it. Good luck

Pat

Just trying to recharge with R-134A won't do it.
As Katatac has said you must evacuate before charging.
Here is the procedure to get your A/C working up to spec.
Purge the system of all old refrigerent. Remove the accumulator and the orifice tube. . Now using compressed air blow out all of the old mineral oil from the lines. Some shops flush the lines with solvent but if this gets into the compressor and is not removed it can burnn it out. Now install a new orifice tube (about $3) and put new O rings on all the fittings that you opened, replace the accumulator with a new one (about $30) and put in about 4oz of PAG oil) . Evacuate to 29.5" HG as above, make sure that the system holds vacuum (no leaks) and you are rady to charge. With the engine off put in one car of R-134A with the can upside down (liquid). After this empties, attach another R-134A can to the low side fitting ( this time upright- gas) and start the engine. Put the A/C on max and continue the recharge until proper pressures are obtained. Depending on the temps high side pressures should be 100-200PSI while low side should read about 25-30psi. The temp cycling switch may need to be adjusted ( screw on the cycle switch under connector) a bit to set the cutoff point correctly

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