I took and passed the MVAC 609 course and received my cert. I just bought 2 cans of R12 and a charge hose with a gauge.

Since my ac only blows warm, I checked the fuses under the hood and can hear the compressor kick on but still get nothing.

I'm going to add a can of R12 w/dye and see if there are any leaks. Do I need to add compressor oil as well?

 

Normally you only add oil when changing components but it wouldn't hurt to add a little. An oz should be good. You also should really draw the system to a vacuum to remove any moisture and make sure it holds before you charge it. Sometimes you can get away with just shooting some refrigerant in.

 

if the system still has pressure in it, your fine with just charging it with r-12 (as long as nothing else is wrong with the system). i also agree i would put and ounce or 2 of oil in it with the r12.

if you hook up your gauges(yes if you are fooling with an AC system you should have gauges/test manifold their cheap) and see that their is no pressure in the system, you will need to find the leak and fix it. then change the oil in the system, then evacuate the system with a vacuum pump and charge it to the proper weight.

 

I'm gonna see if it has any pressure first. I've got some of the r12 w/ dye in it just to see if I can tell what's going on.

Ihor, Do you have a recovery unit?

 

I would add at most a 1/2 oz of oil unless you know that the system has leaked down and then has been recharged several times.

If you open the system up be sure to change the dryer. After being on the car for 15 years on the car it is saturated with moisture and is no longer doing its job. You'll definitely need to add oil if you replace the dryer. See the shop manual to determine how much oil you should put back in after replacing the dryer as well as other components.

Also, if you have access to an electronic leak detector you can charge (BUT DO NOT RUN) the system with R-134a then use the sniffer on it to see where the leak is. This way you can avoid wasting your R-12.