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High and Low Pressure Equal after Conversion


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kprinkki
Novice

Mar 30, 2013, 12:39 PM

Post #1 of 17 (5345 views)
  post locked   post icon High and Low Pressure Equal after Conversion  

I have a 1991 Chevy Corsica 2.2l with about 85,000 miles on it. The AC on the car was not working when we got it and it hadn't been converted to R12. I traced problem to a bad Low Pressure switch. I decided to fix it, bought a remanufactured compressor, new sensor, dryer, fittings for R134a, new O-rings, etc. I evacuated the system and replaced the components, vacuumed tested the system and it holds negative pressure. All good so far.

Now I start charging the system and the low and high side are equal while at an idle run, it doesn't change when I idle up the car either. I have 35psi in the system, but it only took about 16 oz to get there, and I know the system is labeled for 2.25 lbs of R12, so it should be around 2 lbs of R134a. The compressor kicks on and runs. I must be doing something wrong, unless the compressor is bad? Do I have a blocked line? Are those possibilities?. I have been working on this for about 4 days now and I have given up....

Any help is appreciated.

Thanks,
KellyPirate


Hammer Time
Ultimate Carjunky / Moderator
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Mar 30, 2013, 12:46 PM

Post #2 of 17 (5332 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

You have an electrical problem that you haven't found yet. I don't know why the compressor was replaced in the first place but I hope it wasn't for this reason. The compressor should engage as soon as the internal pressure hits about 48 PSI which will happen after less than half a pound is put in. It will need the compressor running to get any more than that in. I hope you vacuumed this system before adding that refrigerant.

You know, A/C repair is much more technical that most people expect. Everybody things it's simple. Very far from the truth. You have to understand how refrigeration works and understand electrical circuits.



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Hammer Time
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Mar 30, 2013, 12:48 PM

Post #3 of 17 (5327 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

I just noticed you said the compressor was running. If that is really true and your pressures are even, you have a bad compressor or you forgot the orifice tube.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



kprinkki
Novice

Mar 30, 2013, 1:10 PM

Post #4 of 17 (5318 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

I did vacuumed the system for over an hour before I started filling and it held pressure for 30 minutes. I put in about 30 psi of R134a before starting the compressor. I didn't want it to run dry. It kicked on right away, so I don't think it is an electrical problem.

I didn't replace the orifice tube. I will look in the GM repair book I have and see where it is located. Maybe that is my culprit....


Hammer Time
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Mar 30, 2013, 1:13 PM

Post #5 of 17 (5313 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

You don't have to control the compressor. Just turn the A/C on full blast. It has a low pressure cutoff switch and will start on it's own when you get enough refrigerant in to hit the trigger pressure. It will continue to cycle on and off until it's near full.



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Hammer Time
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Mar 30, 2013, 1:14 PM

Post #6 of 17 (5309 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

How much oil did you put in the system?

What was wrong with the original compressor?



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



kprinkki
Novice

Mar 30, 2013, 1:22 PM

Post #7 of 17 (5289 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

I put in about 6 oz of synthetic oil. There wasn't anything wrong with the old compressor that I know of. When I first started working on the project, we broke off the fitting for the high pressure side, so we had to replace that section and since we were doing that, someone suggested we should just replace the compressor since we were converting at the same time, it might prevent future problems with the wrong type of Freon and oil in the compressor. I still have it, just in case.


Hammer Time
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Mar 30, 2013, 1:24 PM

Post #8 of 17 (5285 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

I assume that was PAG oil. You should be able to just add more refrigerant and the compressor will start on it's own.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



kprinkki
Novice

Mar 30, 2013, 1:48 PM

Post #9 of 17 (5274 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

Yes it was PAG.









The compressor is starting, but it is not building pressure on the high side.



Should I also replace the refrigerant filter in addition to the orifice tube?


Sidom
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Mar 30, 2013, 1:59 PM

Post #10 of 17 (5268 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

Just a couple of basics I wanted to be clear on......

To be sure the comp is turning on.......There are 2 pieces to the clutch. The pulley & the end plate....The pulley will turn all the time as long as the engine is running....The end plate starts to spin once the compressor is turned on electrically....

Does the end plate start spinning when the a/c is turned on?

Are you using a manifold a/c gauge set? This has high and low side hoses with knobs on both sides to open up both sides, if the a/c is running with both knobs open, you will have low, equal pressure...

When you are charging the system, is the high side knob closed & only the low side open when charging?
What is the pressure reading with both knobs closed?


kprinkki
Novice

Mar 30, 2013, 2:14 PM

Post #11 of 17 (5262 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

The compressor is turning on, the end plate engages when I select in the AC in cab of the car. I have also tested with jumper wire just to make sure. It turns off when I go to vent, heat, etc, so the wire appears to be ok.

I put on a manifold with high/low pressure. I have equal pressure when I open both sides while running. When I charged the system, I only had the low side open and charged to 35 psi - it is about 70° today. The high side still only shows 35. They both show 35 when both closed. I cannot get any cool air to run to the cab.

Just to make sure my manifold was working, I put the manifold on my 2002 GMC Sierra to make sure the manifold was working and it is reading normal.


Sidom
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Mar 30, 2013, 2:32 PM

Post #12 of 17 (5258 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

Well it sounds like HT is on the right track then.......barring any equipment problems, it looks like you either have a comp or orfice problem....

Since you are getting good pressures on your truck, I'm guessing the knobs you are opening are on the high & low fittings on the end of the hoses (which you do need to open to get pressure readings) & not the knobs that are on the a/c manifold....


Hammer Time
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Mar 30, 2013, 2:44 PM

Post #13 of 17 (5251 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

I wouldn't be surprised if there wasn't a shraeder problem with the retro fittings too.



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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



kprinkki
Novice

Mar 30, 2013, 3:41 PM

Post #14 of 17 (5237 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

When I converted, I took the Schrader valves out of the old R12 fittings and I am only using the valves on the new fittings. If it was a bad Schrader valve, I would think I would get cold air, but just a bad reading on the high side.

Yes Sidom that is correct on the knobs.

I am leaning towards the orifice tube. I ordered one and it should be here later this week (remote location so I can't just run down and get one) . I am running out of things to change out...

Here is more update, I changed back to the original compressor and I am still having the problem, so I am ruling out the compressor at this point ( hopefully both aren't bad!). I will pull the orifice tube when I get replacement in.


Hammer Time
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Mar 30, 2013, 3:54 PM

Post #15 of 17 (5232 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

You're going to get yourself into a lot of trouble here and it's could cost you a lot of money. You really need to let a professional deal with this. I can't tell you how many DIY A/C repairs I have to do over completely with even more damage that what they started with.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



jonnblaze
New User

Jun 7, 2013, 4:27 AM

Post #16 of 17 (5060 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

How much oil did you put in the system????Shocked
gHost rIdEr


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Jun 7, 2013, 4:31 AM

Post #17 of 17 (5050 views)
  post locked   Re: High and Low Pressure Equal after Conversion  

johnblaze, please read the FORUM RULES before posting. This thread is 3 months old.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







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