crytical point

I converted my AC to R134a according to the tech article on the site and even had it checked by a professional to be sure. I replaced accumulator, orfice tube, all O-rings, and had the system flushed and vacumed. All oil has been replaced with pag oil and I stuck to exactly how much should be in there. I started filling the system with 134a and about half way through the first 12oz can the pressure went up to 40-48 so I decided to circulate and see if I could get it to go down but it didn't. The compressor would turn on then turn off and just keep doing it so I ran a guage on it and when the compressor would turn on the pressure would drop to like 20.

What could be causeing it because there are no leaks and it couldn't be full with 12oz in it?

Reid Fleming

iTrader: (2)

Are you saying it's going from 20 psi to 48 psi, back and forth?

Or did it go to 48 psi and stay there while the compressor cycled on and off?

When the system cycles off at 20 psi (or wherever you have the cycle off point at), it won't turn the compressor back on until it reaches around 48 psi. So if you have 1 can in there, it should drop like a rock down to the low cycle point and then float it's way back up to 48, at which time the compressor turns on again and it will drop like a rock back down to 20.

Fast355

iTrader: (2)

Jumper around the cycling switch (its the two wire switch on the accumulator) so that the compressor will come on and stay on. Continue to charge. It probably takes 32 oz of R134a to properly charge your system. The high side pressure should not exceed 2x ambient temperature + 50. If its 80*F outside that means you should see about 210 psi. If it is 100*F outside you will see about 250 psi. This varies slightly as conditions change, humidity, engine heat soak, cabin heat soak, etc.

crytical point

It sits at 48 the drops to 20is then goes right back up to 48 the preasure drops when the compressor turns on. and when I jumped the switch it did the same thing. I live in FL its like 90 out side with like 100% humidity

Reid Fleming

iTrader: (2)

With other refrigerents it's been recommended to put about half the amount in and let it idle (cycling) for about 3 minutes while everything balances out. Particularly important when it's a liquid refrigerent. You don't want to put a whole bunch of liquid in at once or else it can smack the compressor and jam up the system. Hence letting it run until it's equally distributed throughout the system.

Reid Fleming

iTrader: (2)

Yep, that's to be expected. We all know about the low psi cycle switch. But our cars won't turn the compressor on until it's at a high number (48).

If they just turned back on at 2 psi above the low cycle point, the cars would cycle non-stop! The off cycle allowing it to go back to 48 also helps melt any ice out of the system.

Typical driving situation: You get in the car, it's been sitting in the sun. It's 90° outside. The pressure of the A/C low side is around 80 psi. You turn the A/C on. It's above the 48 psi mark, so the A/C compressor turns on.....At 80 psi it's blowing maybe 70° into your car. As the A/C gets cooler, the pressure drops. 30 psi being 40°F let's say.

Now since you have very little refrigerant in the car right now, the system doesn't have enough to compress and actually cool properly. To protect the system, the car offs the compressor since the pressure drops below 20 psi.

If you're bypassing the low psi cycle switch, the compressor should stay on no matter how low the psi goes. But that's hard on the system.

Reid Fleming

iTrader: (2)

Anytime the compressor is off, the psi is going to rise. Whether that's switching from A/C to Vent or A/C to OFF or the A/C itself cycling off at the low psi point. When the compressor is off, the refrigerant will start to warm up to ambient temperature.

That's why the up and down on the pressure gauges is so errant at first. When you're finished filling up the R134a, it will probably hover around the 30 psi mark. Occasionally when it cools enough to reach 20, it will do the same rise to 48. Then come back down towards 30 psi slower than it is right now.

By the way, good job on doing this properly rather than a simple drain and fill with $5 worth of R134a low/high side valves. The cheap conversions never work right.

Fast355

iTrader: (2)

I agree on the congrats for doing it properly.

Jumper around the cycling switch and get the compressor going.

crytical point

So I should just fill it to 80psi when its like 90 outside? my guage says thats dangerous and the can starts to frost when I turn the car on and try to fill it froze to my hand (rained earlier).

black89ws6

No. 80 psi, with the system running, is too high. It's not like there's a pressure reading that = ac full. It's a dynamic system, and you really need the whole picture to accurately asses performance. The whole picture, in a nutshell, would be: Low side pressure, high side pressure, ambient air temperature, vent air temperature.

Two cans is mildly undercharged, and may not get enough oil return to the compressor, and poor cooling. Three cans is mildly overcharged, and may result in high pressures, and poor cooling.

The only thing on a gauge that is worth of any attention is psi numbers. These gauges with red, yellow, and green, and danger markings are dangerous. They are encouraging people to tinker with something, without having a fundamental understanding of what they are doing. /rant

You can keep the can from freezing if you charge liquid instead of vapor (hold can with the tapper down(upside down)). On a thirdgen, there is no danger of liquid-slugging the compressor, because the low side fitting is on the accumulator. As long as you let the system run for 2 minutes between cans, you can run in the entire 12 oz can that way.

Fast355

iTrader: (2)

Just be careful doing this, it is exponentially easier to overcharge the system when charging with liquid.

Reid Fleming

iTrader: (2)

No, don't fill it up to 80 psi when it's running. That would be waaaaay too much.

80 psi will be what the pressure is when the system is off and the A/C has been off for a long time (hours). Basically that's the heat soaked pressure.

Fill it until you can keep the pressure around aprox 30 psi.

http://www.aircondition.com/pressure.htm If the system is off and has been for awhile, your refrigerant will be around say 90°F (ambient temp) That correlates to around 85 psi.

When the A/C is turned on, the colder it blows, the lower the psi goes.

An undercharged system that jumps back and forth rapidly from 20psi-48psi-20psi-48psi won't be on long enough to cool the interior down. On the other hand something that's overcharged won't be able to get much below about about 50 psi. That would mean duct temps of mid 50's °F.

crytical point

ok I filled it and got it running but not impressed with the cooling and my compressor is clicking (sorta sounds like a loose rocker arm) and my performance is slim to none.

black89ws6

More information will be helpful. How much did you put in? What pressure is the system running at? Have you inspected the condenser? Is it good and clean?

Reid Fleming

iTrader: (2)

Are you sure it's the A/C and not engine knock? A 2 oz shot of oil might quiet down the compressor. Belts are in good shape? Tight?

What temps are you getting out of your vents? What is the system pressure?

Keep in mind, R134a in Florida with an R-12 based system isn't going to freeze you out. Should be bearable though.

Lucid

iTrader: (4)

What these gentleman are asking is if you have a manifold gauge set like such:
http://www.harborfreight.com/cpi/cta...emnumber=92649

The blue line goes to the low side port and the red to the high side port. The yellow line goes to the cannister (can of R134a).

When they are asking the pressures, they mean what is the pressure on the low side and pressure on the high side on the two separate gauges.

black89ws6

Holy crap! That is a bargain. $45.99 for a manifold gauge set, with R134a quick-couplers, and a sight glass!! Nice!!

crytical point

Condensor is clean, yes the sound is coming from the compressor, it has about 9-10 oz of oil in the system, it is charged to 45psi with the compressor on, and im getting maybe low 50's out of the vents.

The clicking sound is more like a loose rocker arm and it is only there when the compresson is on. I am pretty sure the compressor is going to bite the dust only because it is the original with 188k miles on it. In about a month or so I will replace the compressor and get it working to full capacity.

black89ws6

These R4 compressors are just noisy compressors. That doesn't necessarily indicate a problem. My car is an 89, with it's original R4, still running R12. It's been noisy as long as I've owned it (1999), and always been damn cold. There was a TSB for the R4's in the serpentine accessory mount, for compressor noise. It added an additional support off the back of the compressor to an exhaust manifold stud. I did it to mine, and it helped the noise some, but not completely. I also added a 2 oz can of oil, which also helped some. Since that, I just decided to live with it. That was about 4 years ago, and it still blows cold.

Under what conditions do you get the 45 psi low side pressure? idle, blower high? What is the high side pressure? How much refrigerant did you put in?

Fast355

iTrader: (2)

The compressor might help if it is on its way out. In my experience even a brand new R4 compressor rattles at idle with the blower on high in high heat and humidity. Its just a fact of life with the R134a inability to dissapate heat. If you can find a replacement condensor that is parallel flow instead of tube and fin like the stocker, that will help. A mechanical or LS1 fans on your car would help as well by pulling more air across the condensor while stopped. Low-mid 50s at the vents with the blower on high at idle is about as much cooling as R134a can do. I haven't driven a car with a R134a system that will get into the 40s at idle around here. My 2006 dodge truck with its system designed for R134a, remote mounted condensor and seperate electric fan for the condensor stuggles to reach 50-55* while idling around town. Out on the road it will drop down to about 45*, which is still not all that cold.

EDIT- This condensor from Autozone looks like a parallel flow condensor. I KNOW that the replacement I bought for my 1983 Chevy G20 Van from the same manufacturer was a parallel flow.

http://www.autozone.com/R,APP221389/...ductDetail.htm

crytical point

don't quite remember how much but I know 10oz of pag and the rest R134 but its on the higher side of 40 psi at idle. It works alright but I will have to see and I will refill it if need be I have like 3 cans and an extra pag oil if need be.