Urgent help needed please

[winkawak]

Ignore the charts. They only serve to confuse IMHO.

For instance, at 40 PSI, the evaporator would be around 45 degrees, resulting in center-vent air of more than 50 degrees--hardly enough cooling to provide a comfortable cabin. At 27 PSI, which is what you measured initially, the evaporator would be just above freezing, and it would provide conditioned air of around 40 degrees at the center vent--exactly what you want. That led me to suggest the problem might lie elsewhere and not with the amount of refrigerant in the system.

Measuring 27 PSI on the low side indicates the system is operating correctly and that the Thermostatic Expansion Valve (TXV) is doing its job.

Also note that you can't charge a system by pressures alone. The refrigerant must be weighed-in using a highly accurate refrigerant scale or an RRR machine (Recover Recycle Recharge) that the professional shops use. So a pro shop can recover what's in there now, evacuate the system of all air and moisture, and recharge it precisely to specs. Having that done first would be money well spent, I think.

It sounds like you have a bad o-ring on the low-side coupling. Replacements are readily available, so there's really no need to try another Manifold Gauge Set. What you already have is a high-quality set.

Very glad to learn that you used pure refrigerant.

As first post stated my 2013 mustang gt i have owned since new, its been over 9 years and ac was never serviced, refrigerant must be low by now. Compressor would also cycle on and off often less than a minute and air is not as cool. As of right now im thinking to get my manifold o ring replaced and see if the readings are still the same. I can decide from there whether or not to evacuate the system. Its just weird to me with close to 2 can of refrigerant filled, low pressure gauge not changing, i didnt hear any hissing so i know its not leaking out while charging. Thanks John for the advice.

[tbirdtbird]

There was nothing wrong with your low side reading. Now, since you are overcharged, your hi side is too high. We can only help people who want to be helped. All too often on various forums posters are looking for someone to confirm what they already believe, rather than take the advice offered.
JohnHere is a MACS certified tech and brilliant. Suggest you follow his advice.

[JohnHere]

As first post stated my 2013 mustang gt i have owned since new, its been over 9 years and ac was never serviced, refrigerant must be low by now.

Just because the car is nine years old and the A/C was never serviced during that time doesn't mean that the refrigerant must necessarily be low. It's certainly possible. But the first set of pressures that you posted were right in range and didn't indicate a low charge.

That said, what you could do at this stage is to use an electronic refrigerant detector to "sniff" each joint and all around each component to check for leaks. Visually inspect everything as well for any traces of oil or green-ish fluorescent dye. If you find any signs of such leakage, then you can have the existing charge recovered by a shop with an RRR machine and either have the shop repair the leaks or do it yourself. If you don't own an electronic "sniffer," you might be able to rent or borrow one from a local auto-parts store.

Leaks could be anywhere. But one area to pay particular attention to is the front compressor seal. A good way to check it is to remove the belt and place a shower cap around the clutch and front of the compressor. Leave it set like that overnight or for a couple of days if you have the time, then slip the detector's probe under the shower cap and see whether it reacts. If so, you'll need to replace the compressor.

To check the evaporator, "sniff" around and inside of the condensate drain tube under the car. Refrigerant is heavier than air. If the detector reacts, then the system has a leak somewhere in the evaporator buried within the dash. Most of the other components are readily accessible under the hood.

If testing doesn't turn up any leaks, then you'll need to have a pro shop recover the existing charge, evacuate the system, and recharge to specs as mentioned previously.

Lastly, don't get hung up on the low-side pressure of 27 PSI. That's actually what it should be, and in a correctly operating system, the system will keep it in the range of 25 to 30 PSI regardless of how much refrigerant you put in (within reason, of course).

Mobile Vehicle Air Conditioning (MVAC) is very tricky to diagnose and repair, even for the pros.

[winkawak]

sorry double post

[winkawak]

As first post stated my 2013 mustang gt i have owned since new, its been over 9 years and ac was never serviced, refrigerant must be low by now.

Just because the car is nine years old and the A/C was never serviced during that time doesn't mean that the refrigerant must necessarily be low. It's certainly possible. But the first set of pressures that you posted were right in range and didn't indicate a low charge.

That said, what you could do at this stage is to use an electronic refrigerant detector to "sniff" each joint and all around each component to check for leaks. Visually inspect everything as well for any traces of oil or green-ish fluorescent dye. If you find any signs of such leakage, then you can have the existing charge recovered by a shop with an RRR machine and either have the shop repair the leaks or do it yourself. If you don't own an electronic "sniffer," you might be able to rent or borrow one from a local auto-parts store.

Leaks could be anywhere. But one area to pay particular attention to is the front compressor seal. A good way to check it is to remove the belt and place a shower cap around the clutch and front of the compressor. Leave it set like that overnight or for a couple of days if you have the time, then slip the detector's probe under the shower cap and see whether it reacts. If so, you'll need to replace the compressor.

To check the evaporator, "sniff" around and inside of the condensate drain tube under the car. Refrigerant is heavier than air. If the detector reacts, then the system has a leak somewhere in the evaporator buried within the dash. Most of the other components are readily accessible under the hood.

If testing doesn't turn up any leaks, then you'll need to have a pro shop recover the existing charge, evacuate the system, and recharge to specs as mentioned previously.

Lastly, don't get hung up on the low-side pressure of 27 PSI. That's actually what it should be, and in a correctly operating system, the system will keep it in the range of 25 to 30 PSI regardless of how much refrigerant you put in (within reason, of course).

Mobile Vehicle Air Conditioning (MVAC) is very tricky to diagnose and repair, even for the pros.

Off today, my neighbor is a mechanic helped me bleed some refrigerant out the system today. I also bought a new Pittsburgh manifold to double check my yellowjacket(ripped low pressure hose o ring) readings. With todays temperature around 82-84F, ambient probably close around there too from my new pittsburgh gauges i got 33psi on Low and 270psi on High. I used the pittsburgh hose on my yellowjacket manifold gauges to save time (my low pressure port is not easily accessible) and got readings 29psi Low and 245psi High. Im assuming yellowjacket is more accurate, does these readings look normal? Another thing i noticed is hose are connected other way around with pittsburgh than yellowjacket. For example the end at an angle is connected to the manifold on Pitts and on Yellow its other way around.

[tbirdtbird]

Does not matter which way the hoses go.
Usually the end with the angle is toward the car in order to get around obstructions, but it doesn't matter, there are no check valves or anything in the hoses.
Pressures are better. High side still a bit high.
The real question, is, at those readings, how is the performance? ie central vent temp at 1500 RPM

[winkawak]

i had the ac on max and circulation on with windows down, air feels cool but not ice cold if its makes sense. How do you set it at 1500 rpm? I see article says i might have air in my system but im not sure. If so how i do bleed it without vacuuming the whole system and does having a little air in system hurt it?

[tbirdtbird]

"how i do bleed it without vacuuming the whole system and does having a little air in system hurt it?"

Yes a little air hurts. You can't really do what you asked, which is why we suggested that you have the system evacuated and start from scratch. You seem inexperienced at this. When you charged your 2 cans, did you bleed the air out of the hoses before connecting them to the car? If not, you definitely have air in the system, which will raise the high side pressure and interfere with cooling.

And we are really guessing if you are not able to obtain a small accurate thermometer that you can put into the center vent. It would seem you lack the necessary equipment to really get anywhere meaningful..... just sayin'

How did your hose end get damaged? That would be unusual

[winkawak]

"how i do bleed it without vacuuming the whole system and does having a little air in system hurt it?"

Yes a little air hurts. You can't really do what you asked, which is why we suggested that you have the system evacuated and start from scratch. You seem inexperienced at this. When you charged your 2 cans, did you bleed the air out of the hoses before connecting them to the car? If not, you definitely have air in the system, which will raise the high side pressure and interfere with cooling.

And we are really guessing if you are not able to obtain a small accurate thermometer that you can put into the center vent. It would seem you lack the necessary equipment to really get anywhere meaningful..... just sayin'

How did your hose end get damaged? That would be unusual

I thought forums was a place we can ask questions and learn but it seems since i got here you have been condescending from the start. Why didnt you just said thermometer from the start and no i did not damage the o ring, must been a defect.

[JohnHere]

Does your mechanic neighbor have the proper equipment to leak-check, evacuate, and recharge the system to specs--a good electronic leak detector, vacuum pump, refrigerant scale, and digital thermometer?

To me, the low-side pressures have looked good since your first post, but the high side has been elevated, apparently ever since topping-off the refrigerant--because of an overcharge or other factors.

Air, a non-condensable gas--along with moisture from humidity in the air--could also cause the elevated high-side pressures as already mentioned if there was air in the Manifold Gauge Set and charging hoses that wasn't purged. Of course, any air and moisture in the system will compromise cooling.

It's also very difficult, at best, to top-off a system like that without knowing the exact total weight of refrigerant put in. So it's always best to begin with a thorough evacuation and recharge (for your car, it's 21 ounces net weight of R-134a), along with a receiver/dryer change.

If I were a betting man, I'd wager that once you get the system evacuated and recharged to the exact amount, and barring any leaks or other problems, it'll cool like new.