hey guys, im converting my system over since the a/c doesnt work, im assuming because its got no charge, the a/c hasnt been used in a long time. When i hook up the pressure gauge to the low-side port, the pressure goes up past 100psi into the red. The a/c light lights up but the compressor does not turn. I have not put any new refridgerent in yet due to the pressure in the "red". What do you guys think?

 

is it safe to try to fill the system, even when the low-side pressure is in the red?

 

If there is no charge in the system then both high and low side should read 0. You should capture the charge in the system as the first step.

 

so i figured it out, and charged the lowside till 40psi, the compressor is running, but the air is still hot. I gotta get a gauge set.

 

you need to vacuum the system out first, so it will boil out any moisture, old freon, oil, etc. it should stay under vacuum for at least 30 minutes for it to boil out, if you arent changing anything (you should replace the rec/dryer), then add like 1.5 oz of oil, recharge system. it takes 10% more r134a than it does r12 to charge your A/C, and try it out.

and you should make sure your blend motor and logicon work... i thought my a/c died, but i did a little investigation, and the blend motor was on full hot, and wouldnt move, so i unhooked it until my 'new' one gets here (along with a logicon), and set it to 'chilly'.

also, you should have around an 80psi difference between the high side and the low side, and the low side should cycle, usually it runs until the compressor sucks it down to about 18-25 psi, then it cycles off until it gets back to, lets say, 38-42 psi.

 

How effective is pulling a vacuum with a pump at removing all, or as close to all of the old oil as opposed to opening the system and using some of that a/c flush followed by some compressed air and then pulling a vacuum?

I have a few cars that I need to repair the a/c on and all of them have been opened or are setup for the old r12. So I'm curious on the best way to do this.

 

i think the first two steps might be kind of a moot point, unless they have been open for a while and have dust in them.

i can tell you that you wont get all the oil and moisture out of the receiver/dryer without replacing it. and in order to get all the oil out of the compressor, it needs to be drained, so "they" say. but i havent had any problems at work just evacuating the r12, changing fittings, vacuum for 35 minutes or more if i have other things to do, then add 1.5-2oz of oil and recharge the system.