Automotive Air Conditioning Information Forum

Hello All,
New member on this site and I am hoping you can give me some help on a perplexing problem. I've worked on cars for decades but am a little new to A/C work. A while ago on my 2006 Mazda 3 A/T, the A/C compressor locked up and I replaced it with a UAC kit (compressor, condenser, drier and expansion valve). I have the Mazda Service Manual and I replaced the components as dictated by the procedures in the manual. A/C lines were flushed and blown dry, new seals installed, AC oil came in the correct amount in the new compressor, and system evacuated to 28mmHG and charged to 24PSI Low, 250PSI High (near 100F degree temps) at 1500 RPM. As far as I can tell the 22PSI is about 95F degrees per the manual and I was definitely hotter than that. Hard to read the graph in the manual, but graph goes higher than 22 at near 100F degree temps.

I do not have a scale or any other way to measure the refrigerant charge. I assume that, if a system had the adequate refrigerant amount within its specifications, it would be able to attain the proper pressures in the proper ranges. I.E. proper pressures= proper refrigerant charge…
Problem is, I can only get about 70F degrees at the AC ventilation ports with MAX Fan. All temps taken while car is in the driveway running at 1500RPM (Service Manual spec), 100F ambient temp, with the radiator fan running. Driving it, I can get the AC vent temp down to about 65, but no more.

I am thinking that one of the new components is faulty and leaning towards either the compressor or expansion valve. Or a second theory that I’ve picked upon this site is that if a system has the proper refrigerant charge by weight, and the pressure are off then there is an issue somewhere? If so, what could potentially be the culprit?

Anyone experience something like this or have an idea of where to look for the issue?
Thanks in advance.

So you don't have a scale - so exactly how did you add your R134a? Did you guess from individual cans, to get to the amount of ounces on the underhood sticker of your Mazda? Did you purge your hoses? Did the system hold vacuum (28 is a little low)?

28 is way too low.
Did you use an electric powered vac pump or one of those air compressor powered dillies from HF.
You cannot read vacuum accurately without a vacuum gauge.
If you have the electric powered pump but no vac gauge then you suck it down for AT LEAST one hr and pray.
You will not be able to properly read vacuum level on the lo side gauge on your manifold set.

Cusser wrote: ↑Mon Jul 08, 2024 6:18 am So you don't have a scale - so exactly how did you add your R134a? Did you guess from individual cans, to get to the amount of ounces on the underhood sticker of your Mazda? Did you purge your hoses? Did the system hold vacuum (28 is a little low)?

With modern vehicles, it's very important to get the charge weight exactly correct, as inferred above. Otherwise, the system simply won't function properly.

At only 28 inHg (inches of mercury), it's likely that you still have some air and moisture remaining in the system, both of which are detrimental to performance. If you're at or near sea level, you should see a reading of about 29.9 inHg, or even better and more accurately, 500 microns on a proper micron gauge.

The specifications that I have for your 2006 Mazda 3 are as follows: 18 ounces net weight of R-134a, and 5.0 fluid ounces of PAG-46. If you have an under-hood decal somewhere in the engine compartment that differs, the decal takes precedence.

You cannot charge by pressures. Weighing-in the refrigerant is the only method that will yield the correct amount.

Thanks all for the info.

John H: - "You cannot charge by pressures. Weighing-in the refrigerant is the only method that will yield the correct amount"

This is what I was leaning towards. I'll have the system recovered and recharged with the correct amount. There is a person in my local area that can do mobile AC work or I can take it to him. He recovered what was left of the refrigerant when I initially did the compressor replacement.

Thanks again all for the help!

Ken

Any time!