The first time I increased my psi to 40 psi it blew the high pressure hose. After replacing that, the accumilator, and the orfice tube I again filled it to 40 psi. I'm assuming there's some sort of pop off on the compressor because it released pressure more than once.

What am I doing wrong? I want to fix the a/c, but this is getting expensive. I was at 25 psi before I started messing with it and at least it blew cool.

 

You are obviously putting too much in. I have made this mistake before. What caused my problem? I was filling the system with the A/C levers on max, and the windows closed.

As the evaporator coil in the duct gets colder, the pressure drops. This is really how the cooling is controlled. On a cool day, you will hear the compressor clutch cycling on and off more frequent, because the coil in the duct gets cold enough, that the pressure drops and cuts it off. On a warmer day, the compressor will run more, because the coil in the duct(evaporator) has more warm air going across it, so it stays warmer, and the pressure stays higher.

When I was filling the system, with the controls on max I was re-circulating the cool air inside, and it was getting colder and colder with the windows shut. So the coil is getting colder and colder, so the pressure went lower and lower, and I kept putting freon in it to bring the pressure up. But I was putting too much in because of this.

So now when I am filling the system, I ignore the instructions and put the lever on "normal", turn the fan on it's highest setting, and keep the windows rolled down. This makes sure I am getting warm air over the coil so I can more accurately fill the system. If for some reason your coil is clogged or you are not getting proper airflow through it, you will have the same problem.

 

Thanks Dave. That make sence. Yes, both times the air was on max and the windows were rolled up. I'll try your suggestion.

 

There are charts that show you what pressure to shoot for vs ambient humidity & temperature.

I think 40 on the low side is a bit too high for any condition. As long as you're around 30psi with the compressor on full power you're good to go.

 

Without knowing how old my compressor is where should I start?

Do I rent the vac pump from autozone and vac everything out, then reinstall freon?

If I vac out, how much and how do I install oil?

I tried sucking the oil in through the low port, but it takes forever

 

What is the whole story here? In the first post you were filling the system, and now you are talking about evacuating the system? What freon are you using? Are you doing a r134a retro-fit?

 

Supposedly the PO did a retro fit. I was thinking about vac'ing the system and starting over since I'm still having issues.

 

I can see this turning into a nightmare. Did the PO leave any kind of decal under the hood stating which oil was used? It might be POE or PAG and as far as I know they don't mix. If you want to evacuate the system you might as well drain and flush everything (and replace the accumulator again). That's about the only way you'll know your oil won't gum up. Also make sure you have a R-134a orifice tube. If I remember right, it's the red one.

You can also get a high pressure cut-off for the compressor. I think I got mine at NAPA, but it's been too long to remember the specifics. It will disengage the clutch before the relief vent blows.

I dug back and found this post from when I changed the compressor in our '83. It's a short description of my conversion to R-134a and it might help.

 

An informative A/C thread: A/C Info

-Enjoy
fh : )_~

 

I got the standard orifice tube for replacement. So if I change it to a R-134 tube I'll have to replace the accumiltor again?

 

You'll have to replace the accumulator if you think you may have mixed oils in the system. There's really no such thing as an "R-134a" tube. The original tube will work, it just won't provide the best flow/pressure for a R-134a system. Your register temperature will not be as cold as it could be.

 

Technically ... You are supposed to replace the dryer (accumulator) every time you open the system, however it's done all the time without doing so.

Make sure you vacuum it down and hold it, for at least 30 minutes, before recharging.

Vacuuming down the system boils out any moister as well as shows if the system has any leaks.

-Enjoy
fh : )_~