Help! Complete Rebuilt A/C Pressures Wrong

[Stolidedog]

After a complete rebuild of my 2001 Mustang's A/C system, my low pressure is too low and my high pressure is too high. This indicates a blockage probably in the orifice tube. I live in Arizona in the Phoenix metro area and it is summer and temps are usually above 100 degrees Fahrenheit.

EVERY part on the a/c system is new. Please don't ask me if I replaced this part or that part, I assure you I did. There are only seven main components to it, Compressor, Suction Hose, Condenser, Liquid Hose, Orifice Tube, Accumulator, Evaporator. All o'rings were coated with fresh PAG46 and taken out of the packaging as installed. Proper amounts of PAG46 was added to the accumulator to get it up to specs. Let's assume none of the parts had contaminates. Therefore there should not be a blockage in the orifice tube. Also my orifice tube is pressed into the liquid line so there is no way to inspect it besides evacuating the system, pulling off the line and cutting it open with a hack saw or other similar means.

I replaced the evaporator as much work as it was. I also installed a screen filter in the suction line. Again, all parts were new and I did not remove the plugs to the evaporator, condenser, hoses, accumulator or compressor until it was time to install them. They did not sit open for very long as I was able to assemble things pretty quickly. All o'rings were coated with new PAG46 oil before installation. I also worked in my garage which has a window A/C and reduced overall humidity. No dirt or dust should have been able to enter into the parts. The environment I worked in was clean. I pulled a vacuum of the system for 90 minutes and the vacuum held at -29 PSI. I am certain I do not have leaks in the system.

My Fill Story:

I used pure R-134a freon. 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. You can view the gauge set I purchased here: https://www.amazon.com/gp/product/B019W ... 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 don't know if some or none of it went into the A/C system.

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 was filling. 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. A photo of the can tap with fill line and gauge found here: https://s3-us-west-2.amazonaws.com/mave ... a41bc21a86

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.

Currently my PSI readings are 34/340 (low/high). Given the outside temperature here I should be seeing 50-55 low side and 300-310 high side.

What advice do you have to give? I cannot see how I could have a blockage with all new parts installed, yet pressure readings suggest I do. Could it be something else, like perhaps air is in the system? Would that create a symptom of a blockage?

Thanks for reading!

[Cusser]

I used the Autozone loaner R134a service gauge kit and electric vacuum pump up near Prescott, when most my own stuff was down in Phoenix. I felt both were pretty good units. I used my own can tap though, so not sure why you had an issue with the kit's line.

Currently my PSI readings are 34/340 (low/high).

What advice do you have to give?

I don't agree that you have a blockage.

OK: what rpm were those pressures read? Pressures should be read at about 1800 rpm, and in Phoenix area you should probably have a big fan in front of the grille bowing air in. If high pressure remains high doing that, mist condenser with water and re-take readings.

Your fan clutch or electric fans need to be operating properly too, even if your Mustang engine does not run hot. And your fan shroud must be intact/installed too.

In your case, since you had some issues, I think I'd evacuate, pull vacuum again, and start the fill process again.

[Stolidedog]

I used the Autozone loaner R134a service gauge kit and electric vacuum pump up near Prescott, when most my own stuff was down in Phoenix. I felt both were pretty good units. I used my own can tap though, so not sure why you had an issue with the kit's line.

Currently my PSI readings are 34/340 (low/high).

What advice do you have to give?

I don't agree that you have a blockage.

OK: what rpm were those pressures read? Pressures should be read at about 1800 rpm, and in Phoenix area you should probably have a big fan in front of the grille bowing air in. If high pressure remains high doing that, mist condenser with water and re-take readings.

Your fan clutch or electric fans need to be operating properly too, even if your Mustang engine does not run hot. And your fan shroud must be intact/installed too.

In your case, since you had some issues, I think I'd evacuate, pull vacuum again, and start the fill process again.

I agree with you. I'm taking to to a shop and have it evacuated and refilled. I'll let them do the pressure readings and decide what is right and what isn't. I am taking my pressure readings at idle so maybe that's the problem (or no problem at all). Yes I should have mentioned the radiator fan is working fine and also the radiator is very clean and has no obstructions. I'll let the professionals deal with it now and get back to you.

Thanks for the help!

[Cusser]

I've used Smart Automotive in north Phoenix for over a decade, for any stuff I haven't been able to do myself (I do well over 90% of my own maintenance and repair). They are honest and reliable.

[bohica2xo]

Most likely a service connector issue. Probably never got accurate low side readings based on the charging issues.

May not have achieved a full evacuation either. A common issue with not properly depressing the Schrader valves.

.

[Stolidedog]

Took it to the shop and they pulled out the old freon, vacuumed and re-charged. They found the high side pressure was too high. After investigation on their side (using heat detection gun), they determined the condenser is bad.

I bought the condenser brand new in the box from O'Reilly's. I will be taking it back and get my money back for it, but that doesn't begin to cover the cost of my mechanic's time and materials. This really sucks!

[buiductuan1821]

I am very concerned about this issue.

[DanielJohnson]

I will advise you to get it checked by some professional contractor to get the correct solution to your issue.