How To Diagnose A Bad Automotive AC Compressor With 100% Accuracy 

Awesome, thank you!

Thanks Stephen! Yeah something I learned early on when I was still in my 20's was to not be a parts changer, but instead really learn the system to draw an accurate and educated decision on what is really going on. Even though I haven't done this type of work for many years, I have never ever lost that mind set to not be a parts changer. Wish we could have lived closer back in those days to bounce ideas off of each other. Thanks for stopping by cousin, I really appreciate it! Hope you are doing well!

since I see that you have been a master for a long time, can you help me, I changed the compressor on the car and put a new one, when I turn on the air conditioner, the compressor warms up in two minutes and stops working, what is the problem.

@@yuriboyka3892 There are many reasons why an a/c system won't work properly. It's next to impossible to properly diagnose any A/C system based on a very vague and non descriptive comment with any accuracy. A tech needs to actually hook up and see what is going on with the system to determine the issue.

Thank you, I appreciate that and you're welcome. I enjoy sharing what I know.

It's that time of year for sure! Thanks for watching!

Thank you Bat! I appreciate you watching and you never know, the information could come in handy one day. Cheers!

Thank you, I appreciate you watching!

Thank you too!

Thank you!

Glad you enjoyed it!

Glad you enjoyed it

Thanks Stephen and yes, cars are completely dependant on computers and sensors to tell it how to run. A person just about has to have a degree to even work on them. I certainly miss the old days and old ways. Cheers!

Thanks Frank, I'll be looking for the package and thank you!

Thank you, I appreciate it much!

Thank you! If I ever work on one I will most likely do a video on it

You are absolutely right Frank, everything but TV sets haha! We have a huge one in our living room that I never watch, but my wife does. It's crazy for sure!

I keep forgetting to log into this channel before commenting haha

A oscilloscope can show pulse width modulation and so can a multimeter with a duty cycle function as I shown, but neither will allow you to bypass the ECU and control the duty cycle manually as I did in this video. A bi-directional scan tool could possibly allow you to turn off or on the signal, but not manually control it or at least not to my knowledge. That ability is super handy in diagnosing a compressor.

@@SkillSavvyDIY Great info! Thanks!

I work on gm's. I have found on the new model pickups if you disconnect the stroke valve it does not set codes but the duty cycle will swing wildly from about 30% to 100%. Almost like the ecm is trying to unstick the valve. So it has to have a load on it to get a steady pwm. A tappy tap from a hammer in the area of the stroke valve helps confirm

As of now I’m using a flush bottle with liquid ac flush. A bit messy but I try to capture as much as I can with shop rags.

It could be a few things causing that and really needs to be monitored with gauges as it's being driven at hwy speeds to see what the pressures are doing, but one common reason is being slightly under charged. You are running at higher RPMs at highway speeds and if the system is slightly undercharged, the low side pressure could be dropping to a level that causes the low side pressure switch to cycle the compressor off, but once the RPMs are reduced at cruising speeds, then it's just enough pressure to keep the compressor engaged longer and producing colder air.

Thanks Lance, I appreciate you watching. Not sure what you are talking about with 2 - 60 ac?

@@SkillSavvyDIY Geez I thought you would remember that one, back in day riding in a car without factory AC, you always had 2 60 ac, roll down 2 windows and do 60 MPH

@@SleeperBBQ Yeah, seems like I do remember that! Dang your old 😂

That's something I would have to actually hook up on in order to find out what is going on. There are a couple of things that come to mind, but there again I would have to actually check it out myself. I didn't quite understand what you were saying about adding freon that your pop has that he uses on apartments? Not sure if I understood that or not, but residential air conditioners use a different refrigerant than automobile systems and the pressures run way different.

@@SkillSavvyDIY I'll make a clear detailed video of gauges hooked up and stuff. But I meant that he gets all the types of freon and I have unlimited tries to fix it. Lol. But some people say my problem is in the dash. But anyway my brother did the gauge's hooked up and said it looks normal. But to m something is tripping the high pressure before it's gets real cool. And sometimes is gets real close to 40* but lets up. I'm not sure why it's letting up. And when the cold air lets up a d kinda rises back towards 60. The compressor is engaged and on .

Honestly it could be a variety of things from too much gap in the compressor clutch do to wear making it come on intermittently to being overcharged causing high head pressure to open the high pressure switch or some other problem that can drive up head pressure such as a partial restriction, dirty condenser, and other potential problems but no way of me knowing without physically seeing it for myself

I put a link to it in the video description area below the video.

There are a variety of things that can cause this to happen. Moisture in the system causing the TXV or orifice tube to freeze up after a few minutes of running. A stuck blend door behind the dash causing air to pass over the heater core and evaporator at the same time. A slight restriction in the system. A dirty evaporator causing it to freeze up and force air around instead of through the evaporator, etc. The only way to know for certain is to first hook up gauges and let the pressures tell you where to start looking first. I know this isn't much help but there are various problems that can cause this.

In Addition to what Skill Savvy has already mentioned you might wanna try REplacing the Accumulator Unit, also_ _it too can cause the system to Flip-flop / On sometimes then Off at other times! 😮

I couldn't say for sure without checking the car out like I did on this one, but it certainly could be.

Did you flush the entire system and add the right type and amount of pag oil?

I replaced the compressor, condenser and expansion valve. I flushed the 3 refrigerant lines and evaporator. Yes, I drained the shipping oil that came in the new compressor and added 90cc of Pag 46 that it requires.

Not all electronic variable displacement compressors are clutchless. This model has a ECV as well as a clutch. Some manufacturers starting putting a clutch on their variable displacement compressors so they would not continually spin if the system was low on or out of refrigerant, because oil could not return back to the compressor which would obviously shorten the life on the compressor. The clutch is only there to protect the compressor on this model and the ECU is controlling the compressor output by PWM. The duty cycle percentage is based on the demand sensed by various sensors. The tool I used was tied between the ECU and the ECV valve on the compressor so you know.

Yes I said that in the video but I also explained why I would never change just the control valve if it was the problem, especially on a 9 year old compressor

It is highly unlikely that you would have 3 defective compressors back to back. I would have to actually hook up to the car myself to give you a solid answer on the problem. Just way to many things can cause an AC unit not to cool properly. I hope you find a shop that knows what they are doing.

YOU need to have the power to compressor , fans , ac sensors checked out . that should be one of the first steps. you might have a broken wire or short or connector are bad good luck .

Exactly right

@@SkillSavvyDIY I love working on this stuff. I’ve done it on the side for a few years and have done hvac for the past 2-3 years and I’m done with hvac. HVAc industry is so corrupt. I just quit my job and I’m trying to dedicate 100 percent on automotive heating and air doing something I enjoy.

Good deal! I enjoy it too. I’m retired but I still help folks out

It's not about being worried, it's about being educated. The penalties for any violations of the Clean Air Act include: Civil fines of up to $44,539 per day per violation (as of 2017) Criminal prosecution in US Federal Court (5 years, or double if it’s a second offense) Confiscation of violating substances (refrigerants) Loss of certification to handle refrigerants In addition to the Clean Air Act, which is a federal law, many state and local governments impose additional restrictions. These regulations may be equally or more stringent than those of the Clean Air Act. There is also a sizeable reward for whistleblowers. Of course cars, homes, and buildings leak refrigerant, but laws are put into place to account and minimize this by putting timelines on repairs depending on the size of the leak. It is the act of purposely releasing refrigerant that gets you into trouble. It is impossible to prevent all leaks that happen daily throughout the world and that's exactly why new environmentally friendly refrigerants have and are being developed. I just hope they get it right this time. I can't tell you how many systems I have retrofitted from R12 to R134A through the 1990's to save the ozone and it's like an instant replay because R134A is now being replaced with R1234YF to reduce greenhouse gasses.

If a shop is too cheap to fix or replace their acr machine and blow off refrigerant, do you really want to take your vehicle there?

@@DiscretesignalsExactly

Thank you, I appreciate it! That’s good to know that there are scanners out there with that ability. I plan to pull the trigger on a good scan tool in the near future so I’ll do some homework and see what I can find with that feature. Thanks again, I enjoy your videos as well.

@@SkillSavvyDIY unfortunately, the majority of aftermarket scanners when they do relinquish and allow you to see any HVAC information it sometimes is a limited amount of sensors without two-way communication I’m lucky enough that I work and I’m called into many automotive shops that have factory scanners that give you 100% access Also aftermarket third-party scanners that give you limited access

Yeah, that's been my experience with most 3rd party scanners as well.