You are probably the only one on KZfaq that described the a/c pressure switches. And you make it so simple. Thank you so much. Awesome teacher. You just answered so many questions that I had.

old school; from the basic principles to the schematics. Simply one of the best I've seen around.

This is by far is one of the best video tutorials! I have been a diehard DIYer all my life and have been trying to trouble shoot my ac compressor suddenly not get any power. This has solved that issue. Thanks so much for the help.

Awesome video explaining how system and switches work. You nailed it. Important takeaway - if your relay is clicking, all pressure switches and VCM are working correctly. This is time saver.

I just want to thank you for all the videos you do; they really help a lot of people.

One of the best ac videos on here. Thank you for explaining lingo along with terms. AWESOME!!! Thanks again!

This has to be one of the very best technicians who posts videos like this on You Tube!!! I have seen several videos He has posted and His methods are really good...

One of the best AC trouble shooter videos I've ever seen. Exactly what I needed to continue trouble shooting my 1977 F-350 Diesel AC problem. Thanks, look forward to other videos.

Thank you for an excellent video! You gave me courage to tackle my A/C issue. I found that when briefly bypassing the low pressure switch, the compressor did turn, indicating a need for a charge and probably a leak fix. Five stars from me today!!! :)

Very good informative video I'm glad I watched the whole thing.

Well done! Bringing the basics to the layman! Great video👍

Well done HVAC 101 training, back to basics. Thank you for sharing.

Thank you so much for this wonderful informative video, perhaps tomorrow I can diagnose my Civic.

Thanks for the video D !! It helped me in the field i followed all your training and checked compressor wiring harness all the way back to the PDC everything good .. I found low pressure switch stuck open circuit .. After checking the wiring diagram first i bridged the the plug and the AC system started to work .. The vehicle was a 2006 Jeep Liberty 3.7 V6

Thanks so much for good , clear ,and complete instructions. Just doesn't get any better than this ! ----Ernest E. Johnson

Nice explanation and for using the description of “Interrupter” as well. Having the light and DMM are great visuals for those who learn better this way. I will finish the last few minutes but the P/S switch also effects the circuit. Depending on the manufacture, model and year, but the A/C compressor is interrupted and shut off at high speeds. This can be done using an external switch on the gas pedal, speed sensor at the compressor clutch with steel / iron reluctor and Hall-Effect switch or PM generator that produces an A/C voltage signal, buffered by diodes & electronics shutting the compressor off. Speed or the drivers request for speed reduces damage to the compressor during high RPM’s and helps with performance or fuel economy both during certain conditions. It is nice to see a professional tutorial on the subject. I added info the would make the entire subject harder and perhaps loose some viewers. ASE Master Tech since 1978 - Retired

I am a former ASE certified mechanic, and, in my modest opinion, this guy could very well charge for this teaching on the matters! Very good!

I like your videos, you take the time to track things down logically.

This is the best video on KZfaq explaining the 2 switches. I'm an electrician so this makes perfect sense and for anyone that doesn't have a electrical background just follow this man's instructions step by step and you will be able to troubleshoot your issue. If you cant read schematics dont sweat it and just ignore that part of the vid. Great job to the man that created this vid.

I'm working on making a Frankenstein ac system work, and I've gotta say that this video really cleared things up for me!! Thank you very much! Keep up the good work!

This was the most informative information I have received, and I have gone through hundreds of them here on youtube, you predicated what the other gentleman spoke, you both are on the same page. I did what you and he said and it works, 1988 Lincoln Continental MK VII LSC. Thank you a thousand times.

I used to wire industrial control panels. Your explanation regarding normally closed/normally open pressure switches is very clear. In our schematics we sometimes show the contacts at rest. What we do is indicate on the schematic that the normally closed switch is closed when pressure is above ### and the normally closed is open above ### pressure.

This helped me figure out a problem in my wiring that I'd be struggling with for a few days. The explanation of the wiring diagram is what did it. Thanks for the thoroughness!

One word AWESOME!!! THANKS.

This helped a lot. I just purchased an a/c set up for my truck at a salvage yard but the wiring was all disconected.

Mister you are a MAESTRO.... excellent video thank you

This is exactly the sort of video that I crave (most of yours are). Please keep the in-depth videos coming. I always take something from your videos that help me in my job (if!). A very sincere thanks to you sir!

I have a 2006 GMC sierra pick up truck. The ac quit blowing cold air and I notice the compressor clutch was not pulling in. I checked the fuses in the inside compartment and they were good. I checked the fuses I pulled the relay and checked the coil with an ohm meter and it appeared to be good. 85 Ohms across the coil just like several others that were working. I jumped the contacts on the relay socket and the compressor relay pulled in and the ac blew cold air. So because the fuse was blown and it worked jumped out I though maybe the relay contacts were bad for some reason. I replaced it and had no change. All this time I was getting a 12 volt signal to the relay coil socket. So per your video I set out to check the pressure switches. The low one is a 2 wire and the high one is a 3 wire. I unplugged the 2 wire pressure switch and metered the contacts and had continuity. I plugged the low pressure switch cable back in and all of the sudden the compressor clutch pulled in. The air now seems to be working correctly and blowing cold air. Do I have a problem coming that I should look into?

Superb way of explaining electric circuit's and the testing of,, thank you so much.

Man your video was so informative , it helped me well understand the a/c circuitry , next week id check out my toyota hilux a/c system for ps malfunction and share the results , although the documentary says its a double pressure switch i think it works the same way as you explaind but no idea why theyve called it a double switch!

Smart men! Thank you. Is was very useful for me. Videos like this should be underlined as very well designed and performed educational videos. Thank you again for your time and efforts!

Thank you for the excellent explanation and visual and mechanical demonstration.

really good video, couldn't be more clear. thanks for sharing knowledge.

Awesome video...Thank You!

You video worked. My compressor was clicking on and off fast. Changed the low pressure switch and it just unscrews without loosing the freon. Then it let me add freon. I did jump the switch for awhile to get it to suck up the freon. Thankd

good lesson well spoken and to the point. I get it. my clutch isnt pulling in and now I can test my low and high pressure sensors. thought I was stumped when my fuse proved good and relay was working.thanks

Thanks for making this! I really enjoy these longer in depth vids

Great video. Very helpful. Thanks so much!

wow ...you're great men. it help me to understand how it thank you.

how come all the mechanics that i know, they pretend to know and they do not know shit, this guy in the video is the one you want to know for all your mechanical problems, He is the MAN, and thank you very much Mr.

Need more teachers like him, awesome job sir

THANK YOU FROM VENEZUELA!

Thank you sir !! nice tutorial very straight forward and detailed. ..

This was actually a great A/C Switch Video! 2 thunbs Up!!!

Thank you sir, I have learned something new.

Very informative..Your a very good diagnostic man

🙂 Great video, very well explained and easy to understand. It helped me. Thanks 👍

Love your videos. Thanks!!

Can't make it any more clear than you have explained. Great video.

you're spot on! I like your videos! Doug in Orlando Fl. Walt Disney Fleet mechanic.

This is the best video of ever seen on the air conditions it really helped me out a lot keep up the good work man

Very informative video. Thank you. :)💫👍

This is such a good example and teach video! Thank you!

awesome.... you rock.. keep up the great videos

Very well done, very informative.

gracias muchas gracias esta class me alludo a comprender y lo iso muy bien entendible facil para probar aunque no able Español se entiende con la ilustracion. thanks a lot this class help me I'm learning more thanks again.

Love these videos. i learn so much. idk why but i like electrical work.

Great presentations! Very educational. Thank you for sharing your knowledge in a very practical manner.

the best video on this subject ive ever seen..thank you!!!

excellent lessons , thanks a lot for your time!*!*!

Yes, he'll answer a specific problem for you on his website for $34.95!! Real nice guy!!

Great video! Great instructor!

realy it is fully educated post thanks lot for rich information you had posted

REAL COOL LIKE THE WAY U TEACH THINGS I WISHED I COULD HAVE LEARNED IT MY SELF.MY DAD FIXED 18 TEEN WHEELER'S AND THERE REFER'S BUT HE PASSED 2 YEARS AGO AND I NEVER MEET HIM BUT I INHERITED HIS SHOP AND TOOLS I'M WATCHING UR VIDEO TO LEARN THE BASIC PART SORRY I CAN'T SPELL THAT GOOD IF U CAN'T READ WELL

Very informative. Invaluable information...

Very good video, thanks.

Super video - many thanks :-)

Great video. thanks for the info

Thanks Brother and God Bless BKA Tony

Thanks for your valuable time!!!!!!

As a fellow engineer, I really appreciate your simplistic message.

Great job! Thank you very much.

you are a maestro,nice video

Thank You , well appreciated ..

great video, great info

Great video!

Thank you so very much. This help me a ton.

Great diagnosis

The previous compressor, clutch went bad and it did not cool anymore, It actually broke.Before replacement I flushed the complete system independently. Recaptured the Freon . I replaced with a new compressor, expansion valve, seals. I used a can with a gauge and charged up to 35 psi , everything was working great and cooling. Afterwards I made a mistake of following a generic a/c charge guideline and topped it to 55. I heard the compressor locked up?, sounded lick when a compressor kicks on but slightly louder. The high side on the gauge dropped to 60 and stayed there. Then the car stopped cooling. Removed the Freon and pulled another vacuum, charged to 35 psi and the compressor seems like it kicks on when u press a/c button inside, but the Freon does not flow through the system. After that I have run the compressor about 15-20 min trying to diagnose. My plan is to replace with a new compressor, new a/c switch (pressure switch located next to the high side) and pull a vacuum(1 hour) and recharge correctly. I assume if this is all done again , all should work. Unless the a/c amplifier went bad? It seems its not necessary to flush the system again, since there was no knocking sounds in new compressor and it really did not kick in after over charge. (electrical)-----. To me it seems that the job of the a/c amplifier is to manage power to the compressor and work with a/c(pressure) switch through the wiring and make the compressor run (electrical). Seems that these compressors are smart , have a safety mechanism inside, maybe can be disactivated or maybe they just lock up when over charged. So essentially if electrical is good, the mechanical(compressor and components) then the system should work. Am I missing anything else??. This 2007 is more complicated than a standard car where you only have one cable that runs to the compressor, where you can connect a 12v wire from battery to make the compressor run to check it. This car has 2 leads in the harness and leads me to believe different voltage, cant really be bypassed any where? Also you cant bypass the a/c switch , it has 3 cables.

YOU THE BEST MECHANIC I EVER KNOW THATS RIGHT YOU EXPLAIN THIS REAL GOODDDDDDDDDDDDDDDD

Very instructive. If ever you have time, would it be possible to explain a 4 pin high pressure switch? How to test it.Thank you

I have a 2000 ford ranger. The a.c will attempt to work on startup of the truck, for 3 seconds the clutch will engage and will only if reengage if i turn off the truck and start it again. paperclip trick don't work (pressure switch) refrigerant is good, i know this by running 2 wires directly from the battery to the clutch while the truck is running. the reading on the low side was 35 and the high side 200

That's interesting how different systems work. On older Peterbilts a ground is sent from the dash control through hi and low pressure switches strait to a relay once the control panel is turned on. The key switch feeds power to terminal 86 and 30 is always hot. If there is pressure in the system the ground goes thru hi and lo AC switches and reaches term 85 in the relay and sends 13+ V out 87 to turn the compressor on. Nothing goes through the ECM. Todays trucks might be fed through the ECM though. Its kind of hard to come up with 450 Psi to know for sure that the high pressure switch is working. There really needs to be a way to test that. A Nitrogen tank would do it with the correct connections. Nitrogen is even more handy to have around to test for AC leaks also with soapy spray and pressuring the system. I've seen slow leaks not show up until about 170 PSI. Some leaks take less than 25 psi and boom instant bubbles.

nice training... tanx sir..I'm am ac engineer .

I've seen pressure switches with 3 wires. How do those work? Are they a combination low, high pressure switch?

Great Video sir!

plain simple and great video, thank you Sir....

Smart and anderstandable explanation!

Very informative video! Thank you Sir! Just need some help on my car. Ac clutch stays engaged when ac is on. It does not cycle. Cooling is not a problem. Cabin temperature sensor is fine. Freon charge is okay. I am not sure if it is the cycling switch control that’s making it not to disengage. TIA

Hello Dwayne!!! Can you provide some direction on what to check for when the AC fans don't come on right away on a 2003 Grand Prix 3.8 liter? Clutch engages right away and there is adequate refrigerant in the system. But fans come on several minutes late and then the in-cabin air is cooled properly.

Thank you well explained!

very well presented, thank you

nice,and easy to follow and understand. Thankx

Excellent video

Verry good presentation simple and to the point.

Great video

That's very helpful Thank you

thank you sr good video I DID NOT KNOW THIS BEFORE

Thank you sir for all this information

I try to make this short. I had to change ac compressors from a 96 jeep cherokee to 2000 had to change out backs so lines would fit on 2000. now after having the system vacuumed it wont take freon. I tryied to ground the ac high pressure switch so the clutch would kick in and it will cause the rpms to rise a little but wont kick the clutch in and will blow the big 20 amp fuse under the hood every time. the orig compressor had a ground and 2 wires coming off the compressor vs 2 wires coming off the compressor on the 96 will that make a difference? is my switch bad and wont allow freon to enter.