Automotive Air Conditioning Information Forum

I'm trying to troubleshoot poor A/C performance on a Mazda6s (3.0L v6) with auto controls. It's had poor performance for a couple of years but I wasn't sure the cause. Some days it seems to be almost decent but most blows barely lower than ambient temps.

I checked pressures a while back on a roughly 90F day, it had around 32 on low side and 250 on high side. To me that meant it likely wasn't undercharged. Compressor runs and it didn't cycle. Temps at top of condenser were 175F. I was fairly confinced it was TXV or issue with auto ac blending in heat but I didn't have a way to troubleshoot controls. Then the other night after watching a youtube video on checking supercooling I decided I should check the line temps by hand. I checked up by the TVX and low side was slightly cold but to my suprise the pressure line was cool as well. Checked as close to the condenser as I could reach and it was still cool. Checked pressure line between compressor and condenser and it was very hot, this is also where the high side pressure port is located. My though is this means there is an obstruction in the condenser but I wanted to check here before ordering any parts.

"supercooling"
Your choices are subcooling and superheat, neither of which matters in MVAC

Year? Mileage?

You said TXV, are you sure it is not a CCOT?
The superpros on here can double check that. They often put the CCOT in some weird places.....

It difinetly has an expansion valve. It's a 2004 with 165K miles.

Of course you're right about subcooling/superheat, I had just watched the video because I didn't understand expansion valves and it was the way he was checking from a bad expansion valve on a home a/c. I had heard the terms before but had no idea what they meant. Just made sense that line temp would relate to heat so I figured a cool high side line meant it had lower pressures. My guage reads fine because it's hocked before the condensor. I couldn't think of a way to test pressure after the condenser. Also tried my scan tool and it doensn't show a pressure sensor source.

I'm also not sure if it has a fixed or variable compressor, didn't find much information on google. Compressor is Mazda part number GN3G-61-450A but lists no specs.

I think you've diagnosed it correctly ThisOldBob, restriction at the exit of the condenser, refrigerant flashing there, likely the strainer basket inside the integrated receiver drier (big vertical can on the side of the condenser)

Sounds like you have high superheat coming out of the evaporator, normal for upstream of TXV restriction (starving the evaporator). There was a fellow on here a few weeks ago working on the same vehicle, he did not enjoy pulling the plug to get at the screen and dessicant bag in the condenser, seems the entire front end of the car had to come off first.

Bohica had an easy way for that guy to make the repair (3" hole saw) but the guy did not do it that way and spent 2 days on it ripping the entire front end off the car

Yes I watched a video about replacing the condenser quite a chore. Remove bumper cover, under trays, headlights. Actual bumper and what they call core support. Didn't look like a quick job.

Are you saying the screen and desiccant bag is replaceable? I assumed I'd have to replace the whole condenser and was trying to decide between cheap aftermarket or expensive oem. Don't want to do this labor multiple times. I also figure I should replace the expansion valve while I'm there.

Tbird - I was poking a bit of fun at that guy with the hole saw comment. He got the car for free and had nothing nice to say about it or other members here.

I have no idea if there is a way to truly do that, and do not suggest it for the average car hacker

I have seen videos of new car assembly lines where the entire core support gets loaded with heat exchangers, fans etc - and then installed with the front bumper. Not going to be easy to remove those components later.

oops my bad, thought u were serious!

Screen and dessicant bag are serviceable parts, and very cheap, the screen can actually just be cleaned, but might as well replace it. I don't know how often they are replaced, since you are all the way into tearing this vehicle apart, the entire condenser can be replaced with almost the same amount of work.

The real troubling thought is what the heck has clogged up the screen? Bits of compressor piston coating?

That's exactly how the Mazda 6 was assembled, I was in that plant (Flat Rock, Michigan) a half dozen times in 04-05 time frame. There was a separate assembly area off line where the cooling module was assembled, all heat exchangers went in as one assembly. At that time they were making 3 Mustangs and then one Mazda 6 running down the same line.

This video, about 8:45 in if you are impatient:

https://www.youtube.com/watch?v=lJfA3nrf0mI

That junk will be running around here in August 4 years from now with the windows down because the repair is worth more than the car.