A/C upgrade gone wrong

[okrobie]

Hi all, I recently purchased a truck with a non working A/C. I decided to do the repairs myself. It was an almost empty R12 system. After reading a few articles on the subject, I decided that I could do the upgrade to R134A.

I bought the fittings, a new receiver dryer, a vacuum pump and a manifold gauge set and a 12 ounce can of R134A.

I put in the new fittings and the receiver dryer, attached the manifold and vacuum pump and puled lit down for a few hours, After a few hours I closed the valves and shut off the pump and let it sit for a few more hours. It held the vacuum just fine so I decided to charge The system.

I started the engine and turned on the A/C. I hooked up the freon can and opened the low pressure valve. The pressure came up on the gauges. But then I got a big surprise. The pressure started falling and I was getting a very foul odor from the engine exhaust. and the pressure went to zero,

What happened.? What I do wrong? Thanks for any and all help. Regards, Jim

 

[99LeCouch]

Sounds like a fitting wasn't seated correctly and blew out under pressure. I'd start with what you replaced and double check it for integrity.

Sounds like an older vehicle. Might also have had a bad rubber line somewhere that crumbled from age.

So, double check your work. Maybe add some UV dye into the system so if it leaks again you can find the leak.

 

[bazar01]

Start all over.
Pull another vacuum on the AC system and see if it holds.
If it does not hold vacuum, fix the leak source.
If it holds vacuum, remove yellow hose from vacuum pump. Keep gauge manifold valves closed.
Connect the R134A can to the yellow hose.
Pierce the R134A can.
Purge air from the hose connected to the R134A can and manifold.
With engine off, open the low side manifold gauge valve to charge gas.
You should get pressure now on the system.
Allow pressure to go up to about over 100 psi.
Start the engine and turn on AC compressor.
Compressor should engage.
Charge to correct amount for R134A system.

 

[okrobie]

Thanks guys. That all sounds like good advice. I'm very suspicious of the receiver/dryer. I've never seen that type of gasket before and maybe I put it on wrong. That would also tie in with the exhaust odor. It would probably smell if the freon blew down on the hot exhaust manifold.

EDIT: bazar01, how do you "Purge air from the hose connected to the R134A can and manifold."

 

[yatg]

Make sure you fill it with straight 134A. Not the stuff with the leak sealer.

 

[ford33]

You will also need to know how much R134a to add to the system. One can is certainly not enough and you cannot just rely on the pressure values on the gauges.

Is there a requirement for mineral oil added to the system? Add it now.

I would also add dye to the system right now so you can find leaks quicker in the future.

 

[fitter30]

Two things come to mind. Did you check the oil level in the new compressor? When charging from a vacuum dumping liquid refrigerant in the suction filled the compressor full of liquid and when low pressure switch made compressor engaged it turn to scrap metal instantly. Compressors can't pump liquid. From a vacuum liquid can only be installed in the high side of a system with engine off.

 

[kbeefy]

I didn't see any mention of replacing the compressor.

Don't forget oil. R12 oil doesn't work with r134

 

[TRWham]

You will also need to know how much R134a to add to the system. One can is certainly not enough and you cannot just rely on the pressure values on the gauges.

Is there a requirement for mineral oil added to the system? Add it now.

I would also add dye to the system right now so you can find leaks quicker in the future.

Mineral oil in an HFC system? Bad idea. PAG is generally used in automotive systems with R134a. POE is compatible with 134 and i understand is sometimes used for retrofit in mobile but is the standard for stationary HFC applications.

 

[LS6 Tommy]

Once again I repeat, vacuum cannot be used to leak check.

Tommy

 

[okrobie]

Well, I must admit that I'm human. After my realization that I didn't recognize the gaskets on the Receiver/Dryer, I began to remember that I don't think I ever installed them. I can't work on the truck right now since I have been in the bed for over two days with a major case of Bronchitis. If I'm not better by Monday they think that I should be admitted to the hospital. So I can't check it all out for a few days. I'll let you know what I find when I get to it. I'm pretty sure that I won't find gaskets in the receiver/Dryer fittings. I'm not sure I will find them at a parts store.

read on one site that one of the purposes of using a vacuum pump, was to evaporate or boil off the previous oil. I saw vapors coming out of the vacuum pump exhaust pipe so I was confident that when I saw no more vapors, that I had evaporated all of the old oil. I did read that I should then install the PAG oil. Which is further proof of my humanity since I forgot to follow that suggestion.

I knew that one can of R134A would not be enough, but I'm on a budget and I didn't want to waste a larger amount of R134A. Turns out that that was a good choice of anything I did right.

So, as soon as I recover I'll try to find the right gaskets, purchase some PAG oil and start over. While I'm still here in bed, I'll try to find out the capacity of my compressor, condenser and evaporator etc. Thanks for all of the support.

Unfortunately, I remembered why I haven't been coming back to this site. I'm a slow typist and if I take too long I get a token expired message and sometimes I have to retype my message. (It just happened again. It thought that I was not logged in.) (Fortunately I have learned to make a copy of my message before I hit the send button. I can then log in again and paste my message into a new window.) Even though I have developed a work around, it's still a pain in the a$$.

 

[okrobie]

LS6-Tommy, what is the best method for doing a pressure test?

 

[DavesGarage]

I use a nitrogen tank and charge the system to around 250 psi, close the valve and let it set for a couple of hours and check again. Only trouble is that the pressure will change slightly with the ambient temperature changes.

As mentioned before, you really should read into the lubrication for this upgrade, mineral oil wont last with 134a. Not to mention the different seal materials and larger condenser required for the 134a upgrade.

 

[okrobie]

Hi Dave, I don't have a nitrogen tank, but I do have a 150 PSI air compressor. If I use that for my pressure test, I will have to use vacuum to clear out the moisture and air after I have a successful pressure test. I do have a 200 PSI acetylene thank, but I would be very uncomfortable with that. As long as the system passes the pressure test, I don't mind doing a 2 or 3 hour evacuation.

 

[LS6 Tommy]

Do NOT use compressed air to pressure test. You're just shoving moisture into the system. Dehydrated nitrogen is what you use.

Tommy

 

[okrobie]

Well if I can't use compressed air, I may have to use the acetylene. I'll check tomorrow to see if I have compatible fittings. I know that they use fuel gasses in many refrigeration applications so It will work fine.

 

[LS6 Tommy]

Well if I can't use compressed air, I may have to use the acetylene. I'll check tomorrow to see if I have compatible fittings. I know that they use fuel gasses in many refrigeration applications so It will work fine.

NOOO! Do not **** around with flammable gasses under pressure. What is wrong with doing it the CORRECT and SAFE way?

No disrespect, but you are not the guy to be trying to reinvent this. Just call someone.


Tommy

 

[Wrench97]

Do you have a way to evacuate the system(a vacuum pump)?
If not you are most likely wasting your time and Freon anyway as the moisture will end up freezing to ice crystals in the expansion valve.

 

[fitter30]

You can't evaporate or boil off oil. But, oil vapor or oil mist is a natural by-product of creating vacuum in an oil sealed mechanical pump.

 

[Wrench97]

You can't evaporate or boil off oil. But, oil vapor or oil mist is a natural by-product of creating vacuum in an oil sealed mechanical pump.

What

 

[MattT]

You can't evaporate or boil off oil. But, oil vapor or oil mist is a natural by-product of creating vacuum in an oil sealed mechanical pump.

What

The oil mist you see at the pump exhaust when it's moving air is pump oil not oil being "boiled" out of the system you're evacuating.

 

[Wrench97]

Who is trying to evaporate oil?

When you open a system air and moisture get in, if you use compressed air to blow out debris/oil or look for a leak you get a lot of moisture in and need top put a vacuum on the system to lower the boiling point and remove it.

 

[Lassen Forge]

Well if I can't use compressed air, I may have to use the acetylene. I'll check tomorrow to see if I have compatible fittings. I know that they use fuel gasses in many refrigeration applications so It will work fine.

I hope your next of kin (if they survive the explosion) takes pictures of the results and posts them. I love darwin award photos.

Here's an idea - take an AC course at the local community college before you blow something up. Like your vehicle or home. Take a welding course while you're at it to find out what Acetylene does under pressure.

Acetylene? Seriously?

 

[MattT]

Who is trying to evaporate oil?

The OP thought he was evaporating oil from the system. I guess you missed it.

read on one site that one of the purposes of using a vacuum pump, was to evaporate or boil off the previous oil. I saw vapors coming out of the vacuum pump exhaust pipe so I was confident that when I saw no more vapors, that I had evaporated all of the old oil.

 

[PWC Repair]

It's not like you'll be dumping a glass full of water into the system, a bit of humid air at best! Use your air compressor, I bet I've done it 50 times. 100psi is fine. I've repaired and converted dozens of vehicles for 134a. NEVER had any real issues. I didn't even have a vacuum pump, I made one using an old freezer compressor mounted to a 2x6. What I used to do was pressureize and soapy bubbles to find the leak. Repair it or any other failed part of the system. Pressureize and leak check again. If all good THEN pull your vacuum. Then I would use a bit of the 134a to break the vacuum and zero the gauge. Then pull ANOTHER vacuum. After all that you're good to charge it up. Most vehicles take around 3 cans. After the second can I would get somebody to hold throttle at 1500rpm with AC on max and fan high then slowly add until I had around 40 psi give or take. That always seemed to work best. Learned all this from an old school refrigeration man that was also a hot rodder. I also use to flush out any dirty system by using laquer thinner, a rubber hose, and a funnel. I would use compressed air to push it through. That old guy also showed me that. The only 134a conversions that ever gave me any issues were an F body and a corvette. I got the Corvette going good by purging just a bit out of the system and lowering pressure closer to 30psi. The F body just really didn't have enough condenser for the 134a in traffic. Installed a small electric fan to power up with the AC compressor as on newer vehicles and all was well.

 

[LS6 Tommy]

It's not like you'll be dumping a glass full of water into the system, a bit of humid air at best! Use your air compressor, I bet I've done it 50 times. 100psi is fine. Learned all this from an old school refrigeration man that was also a hot rodder. I also use to flush out any dirty system by using laquer thinner, a rubber hose, and a funnel. I would use compressed air to push it through. That old guy also showed me that.

The "old school refrigeration guy" was totally wrong. I've worked in the industry for over 30 years and most of the methods the "old school" guys used are now considered hack work at best. Sorry, but it had to be said.

Tommy

 

[rlitman]

NOOO! Do not **** around with flammable gasses under pressure. What is wrong with doing it the CORRECT and SAFE way?

No disrespect, but you are not the guy to be trying to reinvent this. Just call someone.


Tommy

Acetylene likes to do really bad things (explode) above 30PSI. There's a reason that acetylene regulators stop at 15 PSI. As Lassen points out, pressure testing with acetylene is an easy way to get a Darwin Award. Please buy a Go Pro before doing this, so your next of kin can at least monetize it.

That being said, while pressure testing with acetylene is deadly stupid, you actually could pressure test on the cheap with propane (though there are legal problems here). Just be sure to keep the pressures below the point that it liquifies. And be sure you have any air purged out of the system, because, well I suspect you have an idea of propane's properties (though then again, it seems that you own acetylene, yet have no clue about what it is capable of).

The "old school refrigeration guy" was totally wrong. I've worked in the industry for over 30 years and most of the methods the "old school" guys used are now considered hack work at best. Sorry, but it had to be said.

Tommy

Exactly. I'm sure the systems he "converted" blew cold air out the vents when he was done. And I'm also sure that unless these cars spend 360 days a year undriven, they'll also no longer be blowing cold air the following season. And after that, you'll need to replace the seized compressors to get them blowing cold air again.

Back to the OP, adding PAG or POE to your mineral oil filled R12 system in the hopes that it will work on R134a is, well, just plain not going to work out for you. And your "budget" that cannot afford more than a single 12oz can of refrigerant, well, it's sadly only laughable. If that's your attitude, I seriously suggest you stop now, before doing more damage.

 

[Awag]

Propane is a direct replacement for r12. The big problem with it is when you get a leak and have 3 foot of flames coming out of your vents. I may or may not have put some in a old vehicle to check if the system would hold pressure. It lasted a week before leaking out. The rest of the vehicle wasn't worth the money to fix it. Cheap way to see before converting to 134

 

[MattT]

you actually could pressure test on the cheap with propane (though there are legal problems here).

Are there "legal problems" using propane for a static pressure test? Or would that only kick in if you ran the system and turned the propane into a refrigerant?

 

[LS6 Tommy]

Propane is a direct replacement for r12.

Except that it is not UL approved for MVAC use...

Tommy

 

[acmikee]

go ahead and use Acetylene might as well throw some oxygen into at the same time but be sure to increase your life insurance first...……………………
its cheaper to pay someone to do a job that you have no knowledge of what your doing before you hurt your self
but if you must use nitrogen to pressurize the system. use soap or electronic for leak checking and a micron gauge
yes you can use co2 or air from your compressor but you'll put moisture into the system

 

[LS6 Tommy]

IBTE

Tommy

 

[Sokoloff]

Except that [propane] is not UL approved for MVAC use...

UL listing is irrelevant.

Flammable replacements are banned by an EPA policy (SNAP), not because UL hasn’t said they’re ok.

 

[LS6 Tommy]

UL listing is irrelevant.

Flammable replacements are banned by an EPA policy (SNAP), not because UL hasn’t said they’re ok.

The UL is not irrelevant. The EPA/SNAP sets policies and regulations. UL and Intertek are the only independent standards organizations authorized by the EPA to certify an item meets EPA requirements. EPA/SNAP have lists of banned, delisted and unapproved refrigerants that are probably more expansive than the UL listings, but AFIK, no refrigerant that is not UL listed is legal. Propane is not EPA/SNAP or UL listed for MVAC.

Tommy

 

[Showkey]

We have had this R12 discussion dozens of times. $20-$40 gets you two cans enough to service your system after the system is inspected and repaired. Assuming the compressor is in serviceable condition.

OP.........you would have been far better off fixing the AC system and refilling with R12 which is readily available. Using a repair guy that knows automotive AC would have far less expensive and 1000 times safer.

 

[TRWham]

R290 and R600 (propane and isobutane) are common outside the US but it may be a very long time before we see them here. I fought this battle 15 years ago but there was no appetite among US equipment or component OEMs to support flammables here. You can have several dozen kilos of propane on your deck or in your RV in a rusty cylinder with 20 year old hoses all day long, but a few hundred grams in a piece of factory assembled unitary equipment scares them to death.

 

[ant.foste]

Flammable replacements are banned by an EPA policy (SNAP), not because UL hasn’t said they’re ok.

A flammable refrigerant is currently being pushed into the US car markers by the EPA as the successor to R134a, which is being phased out. The new stuff is R1234yf, it has an auto-ignition temperature less than 1,000 degreesF, and has FLAMMABLE warnings shown on its packaging.

https://www.refrigerantdepot.com/pr...TDhdxhXgEPDp71-n3fG39o8MLFd3LXxwaAiUcEALw_wcB

 

[ant.foste]

Well if I can't use compressed air, I may have to use the acetylene. I'll check tomorrow to see if I have compatible fittings. I know that they use fuel gasses in many refrigeration applications so It will work fine.

Don't do that.

 

[Milton Shaw]

Use the R134a for the pressure test if you don't have nitrogen. With the system off, gas charge the system with the can upright. That should be good for 100 psi in the system with out using much refrigerant. That will help flush out any air left and help move the moisture out too. Then vacuum it down and charge with the right charge. That should use about an ounce of refrigerant in the gas state to give the pressure to test for leaks. I also always did this with pressure on the high side to see if flow was good and watch the low side equalize out as the refrigerant moved through the expansion device. Some times I have had to use warm water on the can to get the pressure up to where I want it to be.

 

[fitter30]

PWC Repair refrigerant 12 is very for giving. Older systems with mineral oil and holding 3-4 lbs of gas makes them easier to work on. R134a is a blend and has to be in liquid form for charging. The PAG oil is a synthetic hygroscopic oil that open to moisture either in a open container or in a system that hasn't been evacuated properly will compromise the lubrication. Unlike the older systems that you could be down a pound before you had a problem the new systems are a critical charge they hold less than 2 lbs have problems loosing just 2-3 oz. Lp for general use has high levels of moisture and contaminants ranging from 65-95%. As of right now lp is banned for retrofitting.