Hi Scotty, I completely rebuilt my A/C in my 2001 Mustang for the second time. The first time I did…

Stolidedog

Hi Scotty, I completely rebuilt my A/C in my 2001 Mustang for the second time. The first time I did not replace the evaporator but I flushed it quite a bit. I had a problem where high side was too high and low side too low. I took the liquid line off, cut open the tube and viewed the orifice tube and it was plugged with goop.

The second time I followed your recommend and replaced everything again, including the evaporator. All parts band new out of the box, evaporator, condenser, compressor, accumulator, liquid and suction lines. My vehicle calls for 8.6 OZ of PAG 46. The compressor came charged with 3 OZ so I added 5.6 (+- a few millimeters) in the accumulator.

Problem persists. Hot yesterday and high side PSI is around 320 and low side is about 32-33 It should be around 310 high side and 50-55 low side given it was a little over 100 degrees. I think I have a blockage again but I can't understand how?

I used pure freon without sealers or anything else. My radiator is clean and fan works fine. I also put a screen filter in the suction line.

What could I be doing wrong? I'm beginning to loose my mind!

Thanks in advance for your help.

Bob

Comments (18)
No. 1-18
NicoM
NicoM

That really sucks! I don't understand how it can have a blockage if it's new. Could be a variety of things, just bad for you as that was a new part! I hope it will not cost you to much and you can soon enjoy a working AC in your car. All the best!

Stolidedog
Stolidedog

NicoM, I took it to a shop I trust to have them pull out the old freon, vacuum and refill. They did but called me and told me the high pressure side was through the roof. They asked me how much oil I put in and thought maybe I put too much in. Later they determined with a heat detection gun that the condenser has a blockage. They will replace it.

What makes me mad is the condenser is new. I can get my money back for it, but that doesn't pay for the mechanics time and materials which will cost a lot I'm sure. This really sucks.

Thanks for your help!

Stolidedog
Stolidedog

Thanks again. I've been around a wrench or too in my lifetime. I grew up in farm country and my father owned a farm machinery business. I fixed lawn mowers, progressed to tractors and when I became 16 cars. This was in the 70's so things have changed a lot, but I'm a Software engineer by trade so I'm pretty good a researching unknowns and get a good idea of what I'm taking on. Nice to hear from our friends in Germany. I've not spent any time there, but a lot in France, Prague and Bucharest for business.

NicoM
NicoM

No problem Stolidedog, I totally understand as sometimes it is not worth to spend the money if it is something like replacing all the components of an AC system, which of course you are able to do yourself as long as you make sure all the parts match and everything is tight, but with refilling the system I would always leave that up to the professionals. Good job on getting all the components replaced yourself though, must have been fairly difficult to manage! Good luck with getting it fixed, just make sure you tell the mechanic about the potential air in the system and the potential lack of refrigerant and they will know what to check on the system.

All the best

Stolidedog
Stolidedog

I agree with you NicoM, I'm taking it somewhere and will have it evacuated and refilled. I'll let you know how that goes. I also agree with you about DYI. Unfortunately my previous compressor detonated and blew contaminates all through the system. The car wasn't worth spending the money for someone to pull the dash, replace the evaporator and all the other labor involved. I had to save money as things are tight with a new baby and wife going school to get her degree. Thanks for your time on this.

NicoM
NicoM

Edit: Apologies for the long text, the website will not allow me to format it for easier reading.

Sorry for the delay! Right basically the steps I would take here are as follows
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  1. Vaccum the system, the chance there is air in the system seems to be high enough to do this. Ai in the system can cause a wide variety of running problems of your AC and I believe this to be a good starting point

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  1. If the vacuuming does not help, the next step I would take is to evacuate the whole system, get rid of any refrigerant and oil left in it and re fill the exact amount needed as there is too much uncertainty about the quantity that was filled into the system. An incorrect filling quantity, same as the above can also cause a variety of running problems. Your cars AC system has been carefully engineered to run on the volume of refrigerant it prescribes so having this out will affect the components that are designed to run with the prescribed amount of refrigerant.

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Why exactly am I recommending them steps? To give you a quick write up of what I do when designing a refrigeration system will explain why the two points above could play a crucial part in the off pressure levels. Note, I have taken into consideration that all components are new out of the box and have only been fitting, thereby ruling out any component issues.

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When I start designing a system, first of all, I need to know the type of refrigerant used, which in your case is R134a. This tells me the design needs to meet maximum pressure levels of 19bar (~275psi) on the low side and 28bar (~406) on the high side which narrows down my selection of components. Following this, I would need to determine the rough size of the system and running conditions (to, tc, ambient temp etc) to further narrow down my selection.

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The final, but very crucial part is the size of the system I am going to running; this narrows it down a lot further. From that, I make my component selection (comp, evap, condenser, tex etc). Once all components have been chosen it will allow me to calculate the exact refrigerant needed in the system in oz and l. Now should the refrigerant level be off, in the end, it will cause the selected components to run inefficiently, thereby potentially leading to pressure drops, pressure rises as you are currently experiencing.

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Everything used to engineer a system is assuming that the system is free of any air, debris or moisture so having any of these will also cause a system to run unstable and potentially cause fatal damage to your components.

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Personally I always recommend against doing DIY jobs on AC and Refrigeration systems, simply because it takes a lot of skill to keep within the designed parameters of a system and we have had many failed refrigeration plants due to very small mistakes made by our field engineers. I would recommend to spend the cash to get it vaccumed and possibly evacuated and filled by a professional if it costs the same as it does here in Germany (around $200), it will save you alot of potential future headache.

Stolidedog
Stolidedog

Does anyone think possibly between my changing out manifold gauges or something else caused a gulp of air to be sucked into vacuumed system? If so, could that cause too low PSI on the low side and too high PSI on the high side?

What I've read is air in the system can cause the condenser to not efficiently dissipate heat and therefore higher pressure. In the same light it would also cause higher pressure in the low side. Not my case since I'm running roughly 34/340 PSI (low/high).

This is what I've gathered, but I cannot say for certain. I could be wrong. I'm grasping at straws since ALL parts are new and dry when installed.

Thanks

Stolidedog
Stolidedog

NicoM, no worries at all. I so appreciate your concern and willingness to help. Please take care of your business first. I am truly grateful for your help.

BTW, you can call me Bob. :)

NicoM
NicoM

Sorry Stolidedog, have not had a chance to read through it yet, but I will within the next couple of hours (its 5.15am here now and time to get ready for work :) )

Stolidedog
Stolidedog

Thanks again NicoM.

  1. Its orifice tube system and it is compressed in the liquid hose and comes with the hose. The only way to service it is to cut open the line with a hack saw or similar. So the answer is yes.
  2. This is a long story and may be part of the problem. I'll get back to you with a detailed explanation.
  3. I don't know for sure. I didn't have a kitchen scale around. My thought was to buy three cans of 12oz freon and fill the entire two cans and most of the third. My story relates to #2 above and I'll explain more in a later post. Trying to get my son off to school. :)
  4. O'Reillys, tap can 3 x 12oz freon with no additives or preservatives.
  5. No, the caps were removed on all parts as assembled and not before. It didn't take me long to assemble anything as I've been to this rodeo before. I worked in my garage which has a small window A/C unit. It was a little humid here in Arizona because it was monsoon season, but less than most of the country this time of year. The window A/C makes the garage a lot cooler than outside, but not cold. It is super hot here in the Phoenix area this time of year. Anyway, the window A/C should have removed all excess humidity pretty well. Recall I also vacuumed the system for 90 minutes to -29 PSI.

I'll get back to you with a more detailed explanation of 2 and 3 in about an hour or so.

Bob

Followup, here's my filling story,

I purchased this manifold gauge set from Amazon. It works well for measuring PSI and vacuum. This is what I used for performing the vacuum.
https://www.amazon.com/gp/product/B019W5LIVS/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1
The problem with it though is yellow fill line does not directly fit nor have an adapter to that fits a standard can tap, so I wasn't able to use it for the fill.

I went to AutoZone and rented a manifold set from them. I've used theirs in the past and I know how to use it. I connected both the high side and low side to the A/C service ports with both the manifold and service port valves closed.

I then connected the tapped can (closed) to the yellow line on the manifold set. Started the car and opened the tap can valve and the service port valve to fill. Note here I did NOT realize to bleed the yellow line at the manifold set. So potentially air got into the system, but I'm not sure as you read on.

It did not seem to fill at much or at all. The can got a little cold but I also discoved the fittings were not tight at the connection between the tap can and the yellow line and freon leaked from there. I tightend and can got to room temp and never got cold again and nothing seemed to flow into the A/C. I later felt there was something wrong with the AutoZone manifold set and disconnected everything (closing all valves first and car engine shut off). I still have this can connected to the tap. If I had to guess I would say it has 33% to 50% freon inside. Again I cannot account for where the freon that left the can went.

I used the tap can with fill hose and gauge that I had around to fill the car with another can of freon (photo attached). The can got cold and seemed to fill. Meanwhile my compressor was not engaging and I probably got a full can into the system before I realized my high pressure sensor swith was not fully connected, once resolved the compressor clutch would engage and cycle on and off as expected.

I filled another full can (I'm on can 3 now). By now I don't know how much freon is in the system because I don't know how much, if any, freon entered the system because the first can going through AutoZone's manifold set. At minimum I would have 24oz at maximum I would say 28oz.

I started another can because the pressure reading on gauge of the tap/fill hose was rising and the compressor was not cycling as frequently and became fully engaged but still reading the low size (35 PSI or so). I got the pressure up to about 40 PSI and decided to take a high pressure reading.

I used the manifold set from AutoZone and it showed about 5-10 PSI on the low side and 10 or so on the high side. I surmised there was something wrong with this set.

I used my manifold set from Amazon and the low PSI reading was consistent with the guauge tap/fill hose, but the high pressure side was about 350 and that's where I stopped because it was too high on the high side. I didn't not want to continue and risk overcharging the system. So my fourth can probably also has roughly 33% to 50% freon inside.

So it could be slightly overcharged or it could be slightly undercharged. If it is undercharged, the high side PSI should show that as well as the low side. Correct me if I'm wrong. If it is overcharged, the low side PSI shouldn't be showing low. Correct me again if I'm wrong.

If air is in the system, would it show too low on the low side and to high on the high side? Right now my high side reading is probably a couple pounds above where it should be, but my low side is about 15-20 lbs low.
https://s3-us-west-2.amazonaws.com/maven-user-photos/ea88de5e-50e2-4873-a9d3-d8a41bc21a86

https://s3-us-west-2.amazonaws.com/maven-user-photos/18ec744a-384a-4c3b-b7f9-6bb037359242

NicoM
NicoM

No problem! I have had a check and have a few more questions (sorry for all the questions, just trying to get to the bottom of this!)

  1. Did you replace your thermal expansion valve/orifice tube?

  2. When you filled your system, could you explain how you have done so and what you have done to make sure no moisture and/or air managed to get into the system? If this was done by a shop just skip this one.

  3. Did you fill the required 34oz of R134a?

  4. Where did you purchase the refrigerant? Unfortunately, we keep getting problems when purchasing refrigerant from "rogue sellers" as it is often contaminated with blending products and/or air, causing poor performance and in return causing the pressure to drop or the compressor to generally work improperly.

  5. And finally, when you purchased the tubes, did you by any chance have them laying around for a while with no caps on before they were installed?

Should be able to get you a definitive suggestion with an answer to each of these questions above

Stolidedog
Stolidedog

Sure, I purchased after market stuff mostly from AutoZone, O'Reilly's and Napa. I checked everything against the old parts and they seemed to match exactly as the old ones.

Thanks so much for your time on this. I just got it all back together last Saturday night and I've spent the last two days replacing ball joints and tie rods. I haven't had a chance to open it back up yet to inspect. I want to ask someone before I did that as I have no means to evacuate the system again, I have to pay to have it done each time.

NicoM
NicoM

Did you stay all original with the components or did you fit different type components? If you fitted different ones, could you please let me have the make and model of your compressor, evaporator, and condenser and I will check at work tomorrow to get a better idea of what I am trying to help with (I work in refrigeration, mainly industrial systems but car AC systems are fairly simple)

NicoM
NicoM

Well, to be honest, there is a lot of things that can cause this behavior and the pressure drop. 2 of which I have already listed, another two would be a faulty expansion valve or a blockage somewhere as you have already mentioned. You said you have a suction filter, did you check that for a blockage?

When you installed all the new components and fitted new hoses, did you make sure correct dimensions are kept?

Stolidedog
Stolidedog

Thanks NicoM, so you don't think it could be a blockage in the orifice tube? I don't see how it could be but that's what the symptoms indicated. How can check for air other than evacuate and refill? There shouldn't be because I vacuumed for 90 minutes and the vacuum held at -29 PSI, but you never know.

Would you recommend giving it more freon and bringing the low side up to where it should be? I'm just worried the high side pressure will go crazy too.

Also if there was a problem between the evaporator and the compressor, I would think my low side would be too high and my high side too low. The opposite is true. Just curious.

NicoM
NicoM

With PAG46 you need to make sure there is enough R134a to accompany it. Also check for air in the system. Problem is likely to be between your evaporator and the compressor, therefore check thoroughly in that region and let us know once you checked!

Stolidedog
Stolidedog

Thanks Scotty, but as I noted I did replace them. All parts are new. I replaced even the new parts from my previous failed rebuild. Everything.

I don't understand what I did wrong. The only thing I can t think of is when I started to fill it with freon, I couldn't understand why my compressor would not engage. I got about 12oz in and then realized my high pressure switch wasn't connected properly. Resolved that problem and continued to fill as the compressor cycled until full.

ScottyKilmer
ScottyKilmer

Editor

don't forget the hoses, if you didn't change em all, the rubber rotting inside the hoses will clog it up over and over again.