My A/C system pressure is in the normal range checked with two gauges. Fast forward the video below to ~2:45 to see the A/C hold steady at ~45-50psi with compressor running at ~85f degrees for several minutes. At 7:35 I turn the A/C button off and back on and the compressor engages again normally for several more minutes until the car is turned off. A/C blows cold while compressor is engaged. As soon as I turn the car off and back on the compressor attempts to engage one time then turns off and never attempts to re-engage. The only way to get the compressor to try again is to restart the car.


(The R134A recharge can was not open/filling during this video and I did not need to add any refrigerant, the system was already in the normal range when I checked it)

The only way I was able to get the compressor to stay on in the first place was to disconnect the negative battery terminal and reconnect it. The car then attempted to start the compressor 10+ times before finally engaging after ~2 minutes and 45 seconds.

I’ve already replaced the A/C relay on the passenger side near the firewall.

What else would cause this inconsistency of the compressor if the pressure is normal? It always attempts to kick on one time when the car starts but then does not attempt to start again (assuming due to the stored P0532 low pressure input switch). If I disconnect the battery it seems to reset the system more than clearing the code and then it attempts multiple times to engage until it finally stays running permanently)

 

I have very little knowledge of A/C but if you're getting codes that appear after you clear them, gotta deal with them first, cause if there's a fault condition and it thinks there's low pressure, it might disable A/C to avoid wearing the compressor if there's no refrigerant flowing in the system.

If the relay is good, and you're getting pressure on the compressor, how is the pulley and the magnetic clutch holding up? If the pulley and clutch are good, then it might be electrical? Not too sure my dude.

 

Thanks for the insight. I’m going to take a closer look at the pulley and clutch today but it seems strange that once the compressor gets going everything works great. It does seem electrical or a faulty sensor (pressure switch?) since it is just a matter of getting the compressor to stay on. Once it’s on the pressure is perfect and the A/C works great. Then when the car is turned off and turned back on the compressor attempts to come on once (along with the radiator fans) but then quickly clicks off and doesn’t attempt to start again (throwing the P0532 low pressure input code). But the pressure is fine (45-50psi) and the system works great once the compressor goes on.

 

I'm looking for an OBD2 bluetooth dongle that I can use with my Windows 10 laptop, that will report not only engine codes but also HVAC codes, ABS braking codes, maybe even CVT codes. Anyone have any suggestions? I don't want to try and look at a dedicated scanner with its only tiny screen. I want to make a bluetooth connection to laptop computer. Even a usb connection should be ok, or worse comes to worse WiFi although I'd prefer to leave WiFi open for connecting to my smart phone for sharing the internet connection on my smart phones cellular internet service.

At the moment I want to look at the A/C refrigerant codes before hook up a manifold gauge.

Also, I'm guessing that P0534, charge loss, isn't reported unless the charge loss is really severe. My AC functions but it jsut doesn't get the passenger cabin cool enough.

 

I don't know what the AC relay controls so I'm not going to say anything about it.

P0532 means "...refrigerant pressure sensor circuit has low voltage." Because an actual pressure test shows the pressure is normal, probably the sensor is defective, and is reporting that the refrigerant pressure is too low, even though the pressure is actually normal. When the pressure drops below a certain level, the sensor tells the computer to turn off the compressor. Perhaps there is just corrosion where the wire connects to the sensor. I don't know how it fits in to the electrical circuit. I don't know if low voltage means low pressure. It is conceivable that high voltage means high pressure. But given what is happening, low voltage probably means low pressure. When you restart the car the voltage is lowered all over due to the large draw of the starter. Once the car is running the alternator and regulator will regulate the voltage all over. The regulator will change the voltage slightly depending upon how much the battery needs charging and how much current is being drawn by all the electrical devices. If it raises the voltage, say. 3/4 of a volt higher, that might make the sensor go 3/4 of a volt higher. It is just a hypothesis, but perhaps that 3/4 of a volt added to the voltage that the refrigerant pressure causes it to have, might be enough for the computer to think that the system has enough pressure, and turn the compresor back on. Perhaps the AC relay just turns the compressor on with 12 volts, when it gets a smaller votlage, possibly 5 volts, from the computer. So it wouldn't be involved in a problem related to the sensor. The sensor inputs to the computer. Perhaps the AC relay is on the output side of the computer.

I would find out how to check the operation of the sensor. Perhaps you may have to take it out to do that though.So you'd have to recover the refrigerant first, then refill the AC after you put a working sensor back in. You may have to remove the bumper cover to get to the sensor. It should be at the bottom of the condensor. Not sure if it's front or back, left or right.

 

Any update with your issue?

 

Not yet. Been living without AC which has been murder. Not sure what else to look at without evacuating the system and trying to check the pressure switch. It's strange that when it works it works perfectly but the P0532 seems to shut the system off even though the measured pressure is perfect. I wish there was a way to bypass the switch and just force it on since pressure is good and it blows cold when it stays running.

 

I also drove around for only a few hours without AC in weather that was 85 deg F and 60% humidity.. It was murder. Modern cars don't have enough air flowing through. I never felt hot in my air cooled VW beetle, unless I was in stop and go traffic. We need those side-vents that blow air right on your face, that the old cars used to have.

 

This sounds like what I have read is typical behavior of a pressure sensor switch that is not working properly. You may have to remove or partially remove the bumper cover, to get to it. It's on the left side. I've uploaded a picture at another AC thread. At same thread, a schematic diagram although the message board app shrunk it so its blurry. I'm wondering if you can just jump 2 of the terminals, to bypass it. I wouldn't leave it that way as it is there to prevent damage to the system. Too little refrigerant and you damage comrpessor. Too much and you have an explosing.To replace the switch you'll have to first recover the refrigerant. In 2015-2017 the refrigerant is 134a. Some time during the 2018 model it was switched to 1234y.