Automotive Air Conditioning Information Forum

JohnHere wrote: ↑Thu Apr 14, 2022 9:34 pm 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.

winkawak wrote: ↑Thu Apr 14, 2022 10:38 pm 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.

JohnHere wrote: ↑Fri Apr 15, 2022 8:42 am

winkawak wrote: ↑Thu Apr 14, 2022 10:38 pm 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.

tbirdtbird wrote: ↑Mon Apr 18, 2022 6:54 pm "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