Converted a/c to r134, not cooling well

[swb85]

I just replaced my compressor, drier & orifice tube and converted to r134. I pulled a vacuum on it for 45 mins and put 3 cans (36 oz) of freon in. The r12 capacity was 44oz, but from what I've read r134 takes less freon. It hardly cools the air at all, even at max a/c, fans on high and at highway speed....vent temps feel like only in the 60's.
I'm getting all sorts of condensation on the drier/evaporator when it's running and it's cool to the touch (not cold) so I know it's "working", but it's just not getting very cold at all. I see 25-30psi at the low pressure side. Am I over/under charged? Any suggestions? I know little about a/c, so I'm wandering around in the dark here.

[killer71]

that sounds about right on the freon...tell me this does it cool when you get out on the highway or if you put a fan in front of the condensor? You may need a condensor fan the reason I ask to pull/push a little more air across the condensor!

[454HO]

What is the high side pressure?

Why did you change the compressor? Was if bad? If so, in what way? Did you flush the system?

If the old compressor was locked up or making a lot of noise it could have spread metal debri all throughout the system. Unless you flush it really good, this debri will just clog up your new orifice tube.

Did you clean and straighten all the fins on the condensor? Try running water from a garden hose over the condesor and see if the vent temp drops.

[swb85]

Originally Posted by killer71

that sounds about right on the freon...tell me this does it cool when you get out on the highway or if you put a fan in front of the condensor? You may need a condensor fan the reason I ask to pull/push a little more air across the condensor!

The air barely gets cooler out on the highway than when sitting in traffic, but still nowhere near where it should be.

[swb85]

Originally Posted by 454HO

What is the high side pressure?

Don't know, only measured low side with the gauge that came with the conversion kit. Like I said, I know just enough to be dangerous.

Originally Posted by 454HO

Why did you change the compressor? Was if bad? If so, in what way? Did you flush the system?

Because the clutch on the old compressor was bad when I bought the truck 2 yrs ago, and it was cheaper/easier to just replace the whole compressor & convert to r134 than change the clutch and recharge with r12. The old compressor didn't die or lock up, I could still turn it by hand. I didn't flush the system, but pulled a vacuum on it for ~45 minutes.

Originally Posted by 454HO

If the old compressor was locked up or making a lot of noise it could have spread metal debri all throughout the system. Unless you flush it really good, this debri will just clog up your new orifice tube.

The old orifice tube didn't have any debri on it, but the oil on it was almost black.

Originally Posted by 454HO

Did you clean and straighten all the fins on the condensor? Try running water from a garden hose over the condesor and see if the vent temp drops.

I straightened the fins a little, but they were in pretty good shape. No airflow restrictions that I could see, and my radiator behind it gets plenty of air. I did try running a garden hose over the condenser, and the low side pressure immediately went down, but vent temps didn't seem to get any better.

Thanks for all the help guys, I suck at a/c!!!

[72C203503ONTHETREE]

R134 requires more pressure to get close to the efficiency of R12, it wont cool as well with a compressor designed for R12, shouldnt hurt it though. You can use propane as a refidgerant, lol, works better than R12 and its cheap. Theres a couple companies that sell the stuff and its 100% legal.

http://www.maxifrig.com/

http://www.autorefrigerants.com/

I have done some R134 conversions and it usually works ok, try putting a little more in and see what it does. I use a R12 hose set with the plastic can puncturer tool, works on R134 cans but you have to hold the handles since the R134s are larger. You dont need the special connectors then. I never even put a vacuum on the systems either, just hooked up the lines and put a can of R134 in it then released it out, then put the conversion oil and R134 in.

[swb85]

I put in 36oz of r134, but the factory charge said 44oz of r12. You say r134 requires higher pressure than r12 to cool properly, so then wouldn't I want more r134 in the system rather than less for it cool similar to r12 or am I way off track here?......

[72C203503ONTHETREE]

No, it does take less R134 but thats in systems designed for R134, not sure the science behind it but I do know it supposed to run a higher working pressure. Something to do with the molecule size. Oh, and dont smoke while working with R134, when it burns it creates a nerve type gas.

[454HO]

Originally Posted by swb85

The old compressor didn't die or lock up, I could still turn it by hand. I didn't flush the system, but pulled a vacuum on it for ~45 minutes.

The old orifice tube didn't have any debri on it, but the oil on it was almost black.

That is known as 'black death'. You should have completely flushed the system to remove as much of the old mineral oil and debri as possible. Black death is a combination of the old seals, piston rings, etc, ground up into tiny particles. It could eventually cause your new compressor to fail.

Originally Posted by swb85

I straightened the fins a little, but they were in pretty good shape. No airflow restrictions that I could see, and my radiator behind it gets plenty of air. I did try running a garden hose over the condenser, and the low side pressure immediately went down, but vent temps didn't seem to get any better.

Then maybe you need to check that the flapper door for the heater is not in the wrong position. It's possible that your a/c is working ok, but the cool air is then going thru a warm heater core.

Originally Posted by swb85

Thanks for all the help guys, I suck at a/c

No problem, just do some reading. A good place to start is the EPA website. Lots of good info there.

[swb85]

What's the best way to flush the system?

How do I check the flapper door? Where is it?

[454HO]

Originally Posted by swb85

How do I check the flapper door? Where is it?

This was discussed recently. Here are a couple links to help you get started.

http://67-72chevytrucks.com/vboard/s...d.php?t=247921

http://67-72chevytrucks.com/vboard/s...d.php?t=249780

[Duro5341]

R134 is also a smaller molicule, so usually the tech will put alittle bit of dye in there so make sure it doesn't leak.

We did this on my brothers 89 Cavalier RS, believe it or not the original A/C was still working, but needed a top up after 18 years...so to prevent any leaks that weren't there before, because of the smaller molicule, we put some dye in it. This acts like a sealer, and makes it thicker

Worked great, and is ICE cold

Duro

[gchemist]

Use a gallon of isopropyl alcohol. Fill the one tube then use flush it with air. Or use a siphon air hose to push alcohol through the condensor. There is also a special cleaner too. I can't remember the name right now.

[lo04chevy]

When you converted. Did you add the proper oil? Because r12 and r134a is non compatiable. They make a special oil/lubricant that will let the r134a to cope with the r12. Then the r12 will be pulled. You should have pulled the r12 out first. Then change out the orings ,etc... Then pull additional vaccumm to make sure their is no moisture in the line. (It could freeze up). Then add the r134a.

[gchemist]

I would use Freeze 12 instead of R134. I used R134 for a while until the compressor failed. Fixed everything and the second compressor failed. Now I'm moving on to R134 because of the serpentine belt system.

[Slonaker]

Originally Posted by swb85

What's the best way to flush the system?

I went to a local shop that sells supplies to A/C shops. I got a flush gun and a gallon of flush (it smells like acetone...). You pour the flush into the gun, and pressurize it with a compressor. You use it to squirt the flush in under pressure, and then blow it out with compressed air.

It works really well. You just have to break open the lines in a few places to get the flush in there and put it back together with new o-rings.

Slonaker

[KMK454]

Would you guys trust a Chevy dealership to do your AC work? I don't have the tools or time to get mine sorted anytime soon, unfortunately...

[75sierraclassic]

I've done the conversion on my 75 and i've had some problems getting it to cool this summer. From what I've heard, 40 psi is the max on the low side, i never really found out what the high side pressure should be. Is your compressor cycling a lot? This could be a sign that it is low on freon.
I'm just like you, I know just enough to get into trouble Good luck.

[Restrorob]

swb85, 75sc,

You guy's need to get a SET of gauges on your systems so you can read the high side, This is what tells you if you have enough refrigerant in the system or not. Some where in the 325/335 range is good enough.

75sc, 40 is on the high end for the suction side. 20 is perfect and 30 is so so.

[bobbo]

I had a guy in at work that had an 81 suburban with rear a/c and someone had removed one of the lines to the rear unit, he wanted just the front a/c working so I removed the rear line junctions from the front, replaced the compressor, receiver, and orifice, and flushed the front system out very well. The system called for almost 5 lbs. of r12 and took 4.5 lbs. of r134a to cool well and for the pressures to read right. I was getting about 40 degrees out of the vents. He has been back in several times since for other work and the system is functioning great. So maybe you don't need to lessen the freon charge on all systems with a retrofit.

Just my 2 cents.

[swb85]

Update:

Turns out the first numb nut at Napa I talked to told me I needed pac150 oil instead of ester oil for the compressor----wrong. I pulled the a/c system apart Saturday and you should have seen what came out......a thick black bubbling goo. It almost looked alive . Nothing came out of the compressor and it looked good, so I think it didn't hurt it.
So I flushed the entire system out really well, replaced the orifice tube again, put another new dryer on (the black stuff ruined the new one I just put on) and pulled a vacuum on the system for a couple hours. I also wrapped the low side lines with heat reflective tape. I put 3 cans of r134 back in & adjusted my low pressure switch to 21lbs. My low side pressure is now 24lbs. This sucker blows COLD now!!! I drove it 100 miles to KC on Saturday afternoon in 105*F temps and the a/c didn't skip a beat and my temp gauge never went over 195. I did check the flapper door under the dash and the little plastic piece was of course broken, so I still need to replace that. The only thing I need to do now is pick up an idle compensator solenoid for the carb.....it won't idle at all with the a/c on so I have to keep my foot on the gas to keep it alive, and that gets tricky in traffic with a 4 speed!! Thanks for the help guys, I finally have a/c!

[454HO]

[jokersbowtie]

Gratz on getting that working.

mine is cold but the compressor does not cycle off at all