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Discussion Starter #1
My friends car has been lacking A/C for a minute now and two different mechanics have told her something electrical has gone haywire. One of them said it needed to be reprogrammed because the compressor isn't getting a signal from the body computer, or they could install a "switch" so it'll blow cold. Seems very sketchy to me. I told her not to bring it back to that shop. I'm mostly handy when figuring out mechanical issues but A/C system is kind of out of my league. Any advice is appreciated.
 

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Can you elaborate more?

ie;
- does the compressor and clutch work but it’s not blowing cold air.

- A/C clutch not engaging?

- the air is mild-cool, not as cold as it should be

- it’s just blowing ambient air

- radiator fans working normally?

- have the a/c ever been worked on?




Check the basics first.

Check the magnetic clutch relay and fuse first.

And check to make sure both fans operate normally. turning on/off at proper temperature

Make sure AC condenser is clean and not clogged w/debris

Check the lines for visible damage

Who knows,, it could just need a recharge.


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Discussion Starter #3
Compressor is not engaging. We checked relays and fuses. The fans are kind of sporadic. Thermostat code has been on since she's gotten the car but the a/c has worked up until recently. I think fan problem has something to do with fan control module. Before A/C completely stopped working it would go in and out randomly. Tried freon charge and that did nothing did not even blow cold right after. Mechanic said compressor and clutch are fine it's allegedly something electrical with the computer connection to compressor. That's what he says anyway. It just seems like they're trying to take advantage of her after that talk of adding some switch to make it blow cold. Any thoughts? Forgot to mention, A/C system hasn't been worked on previously under her ownership anyway.
 

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did those mechanics do a pressure test on both the a/c Low and High sides? do you remember what those were?

there are scenario when the refrigerant level is improper (too low, or too high). If so, the compressor's clutch will not engage. There has to be certain pressure levels for a/c system to work. Refrigerant level affects the pressure level.

did they hook up their diagnostic tool and check the a/c system? there should be certain parameters and communication signals/data PID they they could verify..

I would double check the relay. if when you turn on the a/c system and the relay click then you should be getting the computer's signal to turn on the clutch. aka your input side is okay. If it's okay then you'd know that there's something amiss w/the load/output side toward the clutch itself or the wiring going to the clutch. basically, split the system into parts and diagnose one section at a time.

I think what they might be thinking is to try to manually bypass the signal and have the clutch run all the time?

if you could check the compressor wiring for breakage, check for power going to the clutch, check the grounding on the a/c housing
 

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I think they must have because there isn't a leak in the system. I didn't get to go with her either time though so I don't have all that information. I think you're right though about what they are probably trying to do which just sounds like bad news to me.
 

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^^ a worn interior switch is also a possibility. when you fiddle with the a/c temp and fan speed adjuster knob does the A/C LED light remain consistently on?

there's also a refrigerant pressure transducer/sensor. If that is faulty, clutch will not engage.

you can do an ohms check on the clutch coil. Typically it should be between 2.0 -5.0/6.0 ohms
 

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Just had an issue with my ac, 04 Mazda 6i, working on drive to store get there stop and it quits blowing. Changed the blower motor, not it, changed fuses, moved fuses, change resistor-which may be your issue. But there's also 2 relay fuses on the drivers side inside car. They aren't labeled (well I'm missing that part, the cover) so never knew what they were. Changed them out and bam blowing again... try those other relays and maybe resistor
 
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