thank you professor for the great video. Would you please help me understand what could be the issue when high side pressure doesn't change whether ac on or off. Clutch does engage when ac turned on. When ac off: low/high side 115/125, ac on; 90/125. No hot or cold when toucing the low/high pipe. Thank you.
You for sure have talent to explain how things operate. Great videos. I would like to know if static pressure is a good indicator for the condition of an AC system. From what I read, there is a good relationship in pressure and ambient temperature. If so I don't understand why on a vehicle the static pressure is 110 on both sides when the ambient temperature is only 75 degrees. Any help would be appreciated. Thanks!
Hi Dave, it is really underhood temperature. So, if the engine is hot, 110 could be the static pressure. Check again when the engine is the same temp as ambient and it should be around 75. Good luck and thanks for watching.
very, very helpful! I just installed a complete ac system in my 1977 Cutlass Supreme, by watching your videos. Evaporator, condenser, comprss, thermo switch, orifice, etc. Bought a vacuum kit and charged it myself. After two wks of running, the comprss locked as I sat at the redlight. Your troubleshooting videos guided me to the fan clutch. AC worked fine if I kept the water hoes on the condenser. No brainer!! Thanks for the info....
Thanks for the video I , I need it to see an actual video of how the fan react, like shouldn't spin more after the engine is off or freely, every other video doesn't show anything like this they all say there should be some resistance only while trying to spin it manually
@Professor, I am really loving your videos. Very helpful. I have a question. I recently replaced my compressor, condenser and the liquid line. I did not replace the accumulator. After vacuuming the system and then charging it. I saw that the compressor clutch engage and we felt cold air. After letting it sit for a bit, we got back in the car and noticed no cold air and the clutch did not engage. We noticed there was no pressure in the system. I noticed that there was liquid coming from the evaporator drain plug. Do you think there is an issue with the accumulator which i do intend of replacing now. or do you think the issue is with the evaporator core. ONe thing to note from your last video that i noticed. The orifice tube is part of the liquid line (2006 Jeep Liberty Sport) when the system was charging, i did notice the liquid was very cold on the side coming out of the condenser before hit the orifice tube. Do you think we compromised the orifice tube. Thanks for any help you can provide.
Professor, I have searched the entire internet with no luck until I stumbled onto your video. I knew with in the first 28 seconds, this was the issue. It was the clip on the condenser fan. Problem solved. Thank you for sharing such helpful information.
Might look into electric fan or fans. It was cheaper for me and supposedly you get better fuel mileage. They come with a thermostat so they know when to turn on. Or you just wire it up to a switch
Today I put gas in my truck in one station to get to another, truck ran famously till I put gas in at the second station.....then it refused go run. I sat from 9:30 am till 5:30 as it refused to run. Had AAA tow me home....everything was fine till the second station. Now I have to go tomorrow and figure out why it suddenly wouldn't run. Tried all day to start it. No dice.....ruined my day. Is there a place that can test a sample to tell you for sure, as I had no problems before...I tried holding the gas pedal to the floor, pumping the pedal, adding carb cleaner to the carburetor.....nothing worked. Never smelled flooded.
The easiest way is to take a fuel sample and check its gravity with a hydrometer, but most people will not have one. It the fuel to too heave, it is the wrong fuel. Will vehicle start and run for a second with starting fluid? If not, this is not a fuel problem. You can also pour fresh fuel into the carb to see if it will start and run for a few seconds. I have an old lawnmower fuel tank that I rig up higher than the carb. Hook the hose from the lawnmower tank to the carb inlet hose and use gravity to feed the carb with fresh fuel. This bypasses the truck's tank, fuel pump, and filter to see if it will run. Good luck, PP
This was a bad design by Dodge. Fan runs all the time even when you are going 70mph. To do this job, you need to recover the refrigerant and take the condenser/fan assembly out.
Thanks for the video. I'm diagnosing a problem with my AC. 1999 Chevy S10 Blazer. Compressor does short on/off cycles continuously. 3 seconds on 3 seconds off over and over. System is clutched fixed displacement compressor, condenser, orifice tube, evaporator, accumulator dryer with low pressure switch. I don't see any high pressure switch anyplace... 70F air outside. Low side looks like about 100 psi. High side goes from 75 psi (compressor off) to 100 psi compressor running). I suspect low pressure switch on the accumulator is bad. Cheap and easy to replace... Should I jump the low pressure switch to see if the compressor is able to build more pressure and bring low side pressure down before wasting time swapping low pressure switch.
Where can I get this file or program, this would make teaching my students so much easier in addition to me drawing on the board and the consolabs we have. Great stuff!
Hi Jason, Sorry but I can not share this file. I have used this video by playing it while turning the sound off during a mobile class in which I had a computer failure. It worked fairly good and I was able to stop and start the video as needed. I also made this video so I would have this animation forever. I had some great animations on flash and lost all of them when flash no longer worked. Good luck, PP
@@ProfessorPentane no worries, I’m a new instructor coming from the dealership after 20 years or so. Teaching yourself is one thing but teaching young minds is totally different and foreign. Thanks anyways
Hi Douglas, you can measure the temperature on the discharge line and then use a pressure/temperature chart on the internet to obtain the approximate pressure in the line. Good luck, PP.
So im assuming with this type of compressor if the ac is on but freon levels are even and not moving the compressor is bad . Or is there a chance that the variable compressor wobble can be at 0% ever. Working on a Hyundai with a clutchless variable compressor.. fuse is good. No errors in the ecm with the ac system. When Activating the ac button freon levels just stay static..
Yes, it could either be a bad compressor or an electrical issue the computer can not detect. Can you command the duty cycle of the compressor with a scan tool to see if it changes?
@@hill_customs6807 You can you a voltmeter like I have in the video and back probe the control wire going to the solenoid. If you are seeing voltage change, the control side is probably good and you have a bad compressor or solenoid. The solenoid should be around 10 ohms.
Awsome video professor! You make this easy to follow and clearly and concisely go over your points of info. As a novice with no experience I've had no issues understanding everything you are demonstrating. Thank you! 😎👍
Awsome video professor! You make this easy to follo. You clearly and concisely go over your points As a novice with no experience I've had no issues understanding everything you are demonstrating. Thank you! 😎👍
I changed the orfice tube in a 2004 ford ranger to a vov tube and had to put in a far amount more freon to get the low pressure up to keep compressor from cycling. Is this normal for the vov orfice tube?
Sorry, but the charge level should not change going from a FOT to a VOV. The VOV is only going to get you a 5 F degrees better cooling during high heat loads, like stop and go driving. It will make no difference during normal heat loads days or driving at hwy speeds with lots of condenser cooling by ram air. It is it not cooling during a normal day, there is another problem. Good luck, PP
Hello professor! Your channel is amazingly insightful full of usable knowledge. Can you recommend a thorough book covering AC operation/theory and troubleshooting? Not that your videos are not sufficient but a written reference is always handy plus I'm an avid reader. I rebuilt automatic and standard transmissions for 28 years. I have now moved in another direction with heavy trucks and equipment diagnosis and repair. I had no previous experience in AC work so I am learning all I can possibly learn. Where your videos shine is your detailed explanations on how a component or system works. If one understands how something works they can essentially troubleshoot any issue. Knowledge is one thing but understanding is everything. Thanks for sharing your immense knowledge and experience. I'm a follower and fan.
Funny you mention a book as I am currently writing and Automotive Heating and Air Conditioning textbook for GW, to be published in 2026, That is why I do not have many videos from this year. This book will have all of my diagnostics for A/C systems that are not covered in any other book. I will post on my channel when the book is available. Thanks for watching.
@@ProfessorPentane That’s awesome! Writing a book is no small feat much less a book on such a complex subject as automotive AC. Can you recommend a book currently available such as your current textbooks you use for students? I will definitely buy your book. Thanks for any suggestions and guidance.
Would this cause the A/C to completely now work? I took it to a shop, confirmed the compressor was working and that it had refrigerant. One of the techs looked at the fan and immediately told me to replace the clutch fan first, that it looked weak, he even put his hand on it while it was rotating. Thanks
Yes, it would cause both low and high side pressure to go very high until the clutch kicked off for too high of pressure. The may work on going down the highway (do to ram air) but would not work in stop and go driving. I hope this helps.
Thanks. This just confirmed it for me. Customer wanted to do an AC install himself. Charged it and it was blowing 60 on a 105 day. Asked him if he put in an orifice tube and he asked what it was. Thanks
Is the clutch even on in the Lincoln, if not, start there? If the compressor is not pumping correctly, the low side pressure will be high and high side pressure will be low.
It is odd that the high side as zero pressure, where is the high side service port? If it is the liquid line, there the condenser or receiver-drier is restricted. Recover again and make sure there is refrigerant in the system before replacing anything.
I have a 96 dodge ram 2500. I think my orifice tube is missing but not sure. The low pressures are high and the high pressures are low. Brand new compressor and condenser. Any suggestions?
If there is no temperature drop through the orifice tube, it is missing. You can feel before and after the orifice tube in the liquid line with your hand. Also, if equalization time if very fast, around 10 seconds, the orifice tube in missing, Normal time is around 30 seconds. I hope this helps. Thanks for watching, PP.
My low side pressure goes all the way up to 150+ p.s.i. when the compressor cycles off and then down to around 50 p.s.i. after the clutch kicks in. It cycles every 5 to 10 seconds. System will blow cold air when driving but not at idle.
Low side pressure could be normal at 150 psi when off if the high side pressure is also 150 with the system equalizing. An orifice tube system will equalize very fast, around 30 to 45 seconds. PP
@@ProfessorPentane I ended up getting proper gauges. Low side when the compressor is ON is 50 p.s.i. but the high side is 375 to 400 p.s.i. When the car is off, both sides equalize to around 120 p.s.i. If the compressor was bad, I don't think the pressure on the high side would get that high. Seems like I have a blockage somewhere in the system, which is a nightmare because I might have to replace several components before I find where it is. It's incredibly hot here too, but garages want $1,500 to $2,000 o repair it when the car in only worth around $4,000 tops.
@@yishihara55527 Make sure the fan is coming on and there is good air flow through the condenser. A dollar bill should be able to stick to the front of the condenser when the fan is running. Poor airflow will cause your pressure to go high. Correct, the compressor is not bad. Which line is the high side service port is on, the liquid or discharge line?
