Troubleshooting help needed-AC pressures

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ACME SS

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I will be calling Classic Auto Air tomorrow with my question and/or to order parts if necessary but first thought I could use a little help from you geniuses out there so I can speak more intelligently when I call.

History: Installed Classic Auto Air 134a system on my Demon. Compressor comes pre-filled with correct amount of oil so you are to install 24 oz of 134a with no oil. I pulled vacuum and let it hold for 48 hours to ensure no leaks. Charged system and it worked great. 2 weeks later the pressure was too low for the clutch to engage and in fact was completely empty.
I once again pulled a vacuum and once again it held for a couple days. At this point I was thinking that if it were to leak down again, it would be nice to have a dye in it but I wasn't sure if it would add to the liquid volume of the system. A mechanic who is certified to work on AC systems assured me it would not. (I am beginning to think I got bum advice) So I charged it again using 1 12oz with dye and 1 12oz without dye. Neither cans said they had oil however I'm suspicious as to what and how much dye or dyed oil is in a can of "dye 134a"? Upon doing this, all pressures were normal, it worked great for a few weeks even though the temps were cool and I didn't really need AC, it worked every time I tested it.
Yesterday we go to a car show and my wife drove the Demon. She turns on the AC and it blows warm air.
I connect my gauges when we got home. Temperature was 90*. Low side pressure was 90psi (I expected 50 or so) and high side was around 75psi (I expected something around 200psi per charts I found online). There was no leak found with my UV light however the evaporator coil is impossible to see as it is in the case under the dash. The low pressure charge port cap however broke when I took it off, leaving the internal threaded portion in the valve, to which I had to spin it out with a pick. My suspicion is that this had possibly been failing after the first charge and the center portion had somehow depressed the schrader valve and was the cause of the first leak-down. see pic below (couldn't find a picture of one with an L on it but it is the same design.

My fear is that the dye may have slugged the system with too much liquid and I may have damaged the expansion valve or compressor? Any thoughts, advice is appreciated. Thanks
Jerry
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Dye has been used for years with no trouble. And you,use the coreprect dye for 134.

Are you sure it has an expansion valve? Most modern systems use a fixed orifice tube and a cycling clutch.
 
Dye has been used for years with no trouble. And you,use the coreprect dye for 134.

Are you sure it has an expansion valve? Most modern systems use a fixed orifice tube and a cycling clutch.
No I guess I am not sure if it has an expansion valve. I did a search on why my pressures would be reversed like that and all I found was a possible damaged expansion valve or compressor. It is all brand new stuff. If it is a fixed orifice then what I found suggested the compressor. I can't imagine how in the world the compressor could have been damaged?
 
If low side is that high, and I assume it is not cycling on the low pressure switch, it is not starved for refrigerant, particularly. Also with low side that high, the metering is not plugged, AKA frozen or debri in the valve/ orifice

You sound like you have some knowledge, but I have to ask, just exactly how did you charge this, AKA what precautions do you take when charging not to slug the compressor?

I do this: With system in a vacuum, and to introduce charge, I always charge liquid into the HIGH side from a vacuum, without powering the system. This gets you an initial charge. Some modern refrigerants (410A) are meant to be charged as a liquid because of their "chemical mix." So you must be CAREFUL and throttle the charging valve to insure you are not slugging the thing.

You are absolutely certain the compressor is running, AKA that the clutch doesn't have a problem?
 
Sounds like you have a leak. You can buy a leak detector on Amazon for about $20. They work really well.
 
If low side is that high, and I assume it is not cycling on the low pressure switch, it is not starved for refrigerant, particularly. Also with low side that high, the metering is not plugged, AKA frozen or debri in the valve/ orifice

You sound like you have some knowledge, but I have to ask, just exactly how did you charge this, AKA what precautions do you take when charging not to slug the compressor?

I do this: With system in a vacuum, and to introduce charge, I always charge liquid into the HIGH side from a vacuum, without powering the system. This gets you an initial charge. Some modern refrigerants (410A) are meant to be charged as a liquid because of their "chemical mix." So you must be CAREFUL and throttle the charging valve to insure you are not slugging the thing.

You are absolutely certain the compressor is running, AKA that the clutch doesn't have a problem?

The manual shows a picture diagram (could be an old generic drawing) which depicts an expansion valve, not an orfice. This is an answer to a previous post by another member.

You are correct...I have some knowledge on this...some, not enough.

As to how I charged it, well unfortunately the instructions they gave do not say which port to use so I followed the instructions on my freon can which stated "Do NOT connect to high pressure side as pressures greater than 170psi WILL cause can to explode". It instructed to connect to low side, have system on and to agitate the can from side to side. I followed those instructions. I never heard any loud noises like the compressor was slugged or anything. Engine never changed rpm, etc., and it did work for like I stated as tested several times over a few weeks. I suppose it is possible the compressor was damaged somehow and now failed but it does not make any unusual noises. Oh and yes the clutch engages and the compressor rotates as evidenced visually and that the pressures were not static or equal. I now see there was a warning on the instruction manual to not shake or tilt the can which contradicts the instructions I followed on the freon can.
 
Sounds like you have a leak. You can buy a leak detector on Amazon for about $20. They work really well.

As I have stated earlier, I did install dye and there are no leaks evident anywhere unless possibly in the evaporator box where you can not see.
 
Find a commercial/industrial HVAC guy and pressure test the system with nitrogen. You should be able to do a 24hr standing pressure test at 200 psi. Sometimes I'll allow a 3-5 psi change to temperature changes over that time. If you have access to a micron gauge, it should evacuate to 200 microns.

CPS VG200 MICRONS, MILLIBAR, TORR and INCHES/HG
 
I don't know You USED to have actual real service valves, you could close the suction side and get some idea of whether the compressor valves were OK You might try to recover the regerant, or as much as you can, and then "rig" a fitting to your vacuum gauge force the compressor to run and that would give you some idea. You can also run it for a short time in the same way and see what it will compress for air pressure on the outlet. That is again, a matter of being able to rig appropriate fittings

So far as the pressure limits on the can, you do NOT charge into high side when running. This procedure is for initial charge. You have a vacuum on the system, and NOT powered. You simply dump liquid into the high side. This gets a lot of refrigerant in, quickly. It won't hurt anything, as the liquid goes around, through metering, through evap, and back to compressor. It will be vaporized by that time.
 
Find a commercial/industrial HVAC guy and pressure test the system with nitrogen. You should be able to do a 24hr standing pressure test at 200 psi. Sometimes I'll allow a 3-5 psi change to temperature changes over that time. If you have access to a micron gauge, it should evacuate to 200 microns.

CPS VG200 MICRONS, MILLIBAR, TORR and INCHES/HG
I think you are imagining things. Hoses leak, and oil boils off refrigerant. I doubt you can pull a true 200 microns on an automotive system and get it to actually hold. Just the oil in the system alone is likely enough to trash that
 
What makes me a little suspicious here is the fact that it didn't change RPMs when the clutch engaged?..
If it's leaking out one of the Schrader valves that's a great easy fix but on the other hand it's hard to detect because there's always a little bit there from when you put it in. So your black light will show some there whether you've got a leak or it's just where you put it in at...
But again the compressor not dropping the idle down one or 200 RPMs is a little odd to me...
 
No I guess I am not sure if it has an expansion valve. I did a search on why my pressures would be reversed like that and all I found was a possible damaged expansion valve or compressor. It is all brand new stuff. If it is a fixed orifice then what I found suggested the compressor. I can't imagine how in the world the compressor could have been damaged?
If it's a TXV they can fail open but in that case the low side will be too high, there will be little to no superheat, and the high side will be too high. High side of course is affected by OD temp as well as load.

Are you certain when you took pressure readings that you had the manifold valves CLOSED?
 
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I installed one of their systems and I recall specific instructions to NEVER charge with liquid, only gas or else damage will occur to the compressor. Ask them about this when you call.
Usually the dye cans are oil with dye in it. Check your can and see. I use a dye injector so I know im only putting dye in. Anyhow, hopefully you didnt put too much oil in the system because if you did your looking at a flush and that can be a lot of work.
 
I don't know You USED to have actual real service valves, you could close the suction side and get some idea of whether the compressor valves were OK You might try to recover the regerant, or as much as you can, and then "rig" a fitting to your vacuum gauge force the compressor to run and that would give you some idea. You can also run it for a short time in the same way and see what it will compress for air pressure on the outlet. That is again, a matter of being able to rig appropriate fittings

So far as the pressure limits on the can, you do NOT charge into high side when running. This procedure is for initial charge. You have a vacuum on the system, and NOT powered. You simply dump liquid into the high side. This gets a lot of refrigerant in, quickly. It won't hurt anything, as the liquid goes around, through metering, through evap, and back to compressor. It will be vaporized by that time.
Gotcha! That is what I was hoping you meant.
I might just find a refrigerant professional and have them look at it. I hope I didn't damage it with liquid...I read not to use liquid but I was thinking it was gas coming out of the can since it had to travel vertically 3' to get to the manifold but what do I know? I like to learn and do everything myself but sometimes I think I spread myself a little too thin. LOL
 
I installed one of their systems and I recall specific instructions to NEVER charge with liquid, only gas or else damage will occur to the compressor. Ask them about this when you call.
Usually the dye cans are oil with dye in it. Check your can and see. I use a dye injector so I know im only putting dye in. Anyhow, hopefully you didnt put too much oil in the system because if you did your looking at a flush and that can be a lot of work.
I looked up the Chemours 134a with dye that I had used and it is simply uv dye with freon, no oil is mentioned.
 
If it's a TXV they can fail open but in that case the low side will be too high, there will be little to no superheat, and the high side will be too high. High side of course is affected by OD temp as well as load.

Are you certain when you took pressure readings that you had the manifold valves CLOSED?
OK, now I understand how these gauges work....I'm a complete IDIOT!
I found a cutaway drawing... All right, I need to re-evaluate my situation as I probably messed it up. So my manifold valves were open but the charge hose was parked on the manifold so I'm not sure if it mattered or not if it was open because the fill hose was not hanging open to atmosphere?
 
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I went to only using the high side valves for the vacuum... After I vacuum the system down I generally close off both high side valves the one on the gauges and the one down on the high side valve on the unit itself. I actually take it off at that point. Then after it holds 30 negative pounds for a few hours I go ahead start the car turn the AC on high and start charging the system. And definitely when I open the can I purge the lines...
I'm not saying this is "the" way to do it but it's the way I do it...
 
OK, now I understand how these gauges work....I'm a complete IDIOT!
I found a cutaway drawing... All right, I need to re-evaluate my situation as I probably messed it up. So my manifold valves were open but the charge hose was parked on the manifold so I'm not sure if it mattered or not if it was open because the fill hose was not hanging open to atmosphere?
YEH!! IT MATTERS!!! This is a standared 2 gauge manifold with 2 valves and 3 hoses? To only measure pressures, CLOSE both manifold valves. The ports from the hoses go straight to each gauge.

When you open either valve, the center port is now connected to that hose and gauge. So with both valves open, "everything" is interconnected

Here's how I do, "let's say" you have it all charged up and running. If we have schrader (tire core) service ports, I use what is called a "schrader controller." This is a rig that looks like a small valve, goes on the fitting, your hose goes onto the controller.

If you have service ports with closeable ports (valve stems) you don't need that

So, "let's say" you have it all charged and running good. You don't want to waste refrigerant, so here's how to unhook. Both manifold valves are closed. You have purged the hoses on hookup, and the charging can is sitting there on the third port empty.

Unhook the charging can, hook the middle hose to the storage fitting on the manifold. Crack the low side valve and purge the middle hose to the storage fitting, then tighten. Now the manifold is again purged and leak tight

So now close the high side service valve, or back off your Schrader controller. Then open the hi side valve, and next, slowly open the low side valve. This causes the compressor to suck everything in the manifold/ hoses, into the low side. There will of course be "low side pressure." Let it set a few seconds to evaporate liquid. Then close valves, close off the low side if needed, and disconnect the hoses

Connecting. I usually try and connect before turning on system. Of course if charging/ evacuated this does not apply. Make sure manifold valves are closed, hose fittings tight, and third hose tight at storage fitting. Connect hoses, open low side service port, and purge by opening low side valve, purge through center hose by loosening at the storage fitting, and then open hi side valve and purge out to end of hi side hose by loosening hi side hose at service port. then close both manifold valves, make sure all hose/ fittings are tight, and open hi side service port.

Again, MAKE SURE both manifold valves are closed
 
I think you are imagining things. Hoses leak, and oil boils off refrigerant. I doubt you can pull a true 200 microns on an automotive system and get it to actually hold. Just the oil in the system alone is likely enough to trash that

Well, yes, 200 microns might be a little optimistic. Force of habit with some of this process stuff with -40 evaporators. Specs for VRF is 50 microns to hold.

A good shaft seal is always the trick. Good hoses don't leak, as you well know. But I was always surprised the auto industry doesn't adopt nitrogen for test and purge like the rest of the HVACR industry. But I stand by what I said - a standing pressure test at 200 psi.
 
OK, now I understand how these gauges work....I'm a complete IDIOT!
I found a cutaway drawing... All right, I need to re-evaluate my situation as I probably messed it up. So my manifold valves were open but the charge hose was parked on the manifold so I'm not sure if it mattered or not if it was open because the fill hose was not hanging open to atmosphere?

Any updates?
 
Any updates?
Update:
So after I learned how the gauge set is valved internally and that the pressures probably were not reversed but simply affecting each other cause I didn't have the valves properly configured, I discovered I was loosing freon due to a sudden pressure leak. Because there was dye in the system, I quickly discovered it was the crimp connection between the hose and the LP compressor outlet tube (with the LP port on it). It got so bad at one point that it started to hiss and by the next morning the system was empty. This happened around 10pm so I could not take it anywhere to have what was left evacuated properly. I removed the hose and put it back in my crimp tool and was able to get a little bit more of a crimp on it. I pulled a vaccum and it held but I really wanted to pressurize it with argon or something but didn't feel like making up the connections so I decided to take it to a shop where they could pressure test it (not just pull a vacuum) since it had tested OK under vacuum but leaked under pressure.
The shop says sure, we can do that. Two hours latter I get a call that it is finished and I was a little miffed because I expected them to pressure test and pull a vacuum and to leave it long enough to be sure it isn't leaking in either condition. I highly doubt I will return to them since they didn't do what I asked. (not that I take my cars to shops more than once a decade as it is)
I pick it up and they say that I fixed it. I asked if they pressure tested it and they said no... I explained that the reason I brought it to them was to pressurize it in addition to evacuating it. Got that glassy stare back like I have 3 eyeballs.
Then I get home and see the invoice says they added a NAPA 134a with oil in it. I go to NAPA and get the specification on the part number and calculate they added 4 oz of oil to the system which is factory filled with 7oz and no more is to be added. At this point I wish I had just spent the time to plumb in argon or something and pressure test it myself. But I go back and kept my cool and confronted them concerning the oil and they say, "oh the computer just uses that part number (which is for a 14oz can) but we really used our cart which has 134a only in it".
And this my friends is why I would rather bumble around these things myself.
I'm not sure if it is really fixed yet. It blows cold but whether or not it will leak is to be seen. I cleaned some dye off the area this morning that I am hoping is from them when they disconnected their hoses.
 
Update:
So after I learned how the gauge set is valved internally and that the pressures probably were not reversed but simply affecting each other cause I didn't have the valves properly configured, I discovered I was loosing freon due to a sudden pressure leak. Because there was dye in the system, I quickly discovered it was the crimp connection between the hose and the LP compressor outlet tube (with the LP port on it). It got so bad at one point that it started to hiss and by the next morning the system was empty. This happened around 10pm so I could not take it anywhere to have what was left evacuated properly. I removed the hose and put it back in my crimp tool and was able to get a little bit more of a crimp on it. I pulled a vaccum and it held but I really wanted to pressurize it with argon or something but didn't feel like making up the connections so I decided to take it to a shop where they could pressure test it (not just pull a vacuum) since it had tested OK under vacuum but leaked under pressure.
The shop says sure, we can do that. Two hours latter I get a call that it is finished and I was a little miffed because I expected them to pressure test and pull a vacuum and to leave it long enough to be sure it isn't leaking in either condition. I highly doubt I will return to them since they didn't do what I asked. (not that I take my cars to shops more than once a decade as it is)
I pick it up and they say that I fixed it. I asked if they pressure tested it and they said no... I explained that the reason I brought it to them was to pressurize it in addition to evacuating it. Got that glassy stare back like I have 3 eyeballs.
Then I get home and see the invoice says they added a NAPA 134a with oil in it. I go to NAPA and get the specification on the part number and calculate they added 4 oz of oil to the system which is factory filled with 7oz and no more is to be added. At this point I wish I had just spent the time to plumb in argon or something and pressure test it myself. But I go back and kept my cool and confronted them concerning the oil and they say, "oh the computer just uses that part number (which is for a 14oz can) but we really used our cart which has 134a only in it".
And this my friends is why I would rather bumble around these things myself.
I'm not sure if it is really fixed yet. It blows cold but whether or not it will leak is to be seen. I cleaned some dye off the area this morning that I am hoping is from them when they disconnected their hoses.

Oh boy. I know how you feel. I'm going to have my system (classic auto air) redone. I had a shop charge it, but the tech didn't really seem to want to follow the instructions, and it doesn't blow nearly as cold as it should over 40* on the thermometer.

He only pulled a vacuum for 30 mins (new systems say 90 min).
 
Man o' Man some of this advice is WAY overcomplicating this procedure. I have been doing this professionally for a long time, and some of these replies had my head spinning. KISS !!
 
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