How does an Automotive A/C System work: Part 4 FOT and VOV Diagnosis

Learn how a Fixed Orifice Tube and Variable Orifice Valve A/C system works on a mobile vehicle. This is a beginning lesson on mobile A/C for anyone starting to work on Air Conditioning on cars, trucks, or mobile equipment.

[@creepycrawler43]

Exactly what I was looking for

[@coldfinger459sub0]

Your channel was just recommended to first time I came across it very good content thank you for taking out the time to post there’s a lot of students and older mechanics who need this information. Takes a lot of time and effort to edit and choreograph a professional looking video something I don’t have time for.

[@ignatius2230]

These automotive AC classes are a big help wherever you see from, even If you think you know enough its a very solid base of knowledge, so thanks for that Air conditioning on cars evolved too much nowadays, since its the same principle as an oldschool system HVAC control units are acting over a certain quantity of components that older systems doesnt have like thermistors, control valves and controlled servos where every signal has their own role, like cabin humidity, duct temperature, wss signal to control condenser fan speed, solar sensors... and a few more tricky things that I dont even know. There isnt clever information from car manufacturers about how these systems really works, even refrigeration professionals says automotive AC is a very weird thing compared to big industrial systems, maybe because the lack of info to understand it. So thanks again to "condense" all the knowledge in a very well explained videos like these, hope more people appreciate those

[@handydaddy4232]

Thank you professor! I was concerned about the hissing sound I hear where the orofice is after shutting off the car but now I know it is completely normal.

[@francisdsa6790]

Thanks professor very nice demonstration and information value able video 💐💐💐💐💐👍👌👌🙏🙏🙏🙏

[@lisab3396]

I love the clear and precise illustrations and teaching intructions. The reason I am even here watching this is because 1) after just 1.5 years my new compressor failed/leaked at the front seal behind the clutch. 2) Buying a new compressor, orifice tube and accumulator, I have just discovered that the Pro A/C shop doing the work had/has installed the fixed orifice tube in backwards. My question is, What problem affect if any would this cause with reversal of the OT? The A/C seemed to work fine until recently. We are in Canada and so we don't use A/C for half the year. As a final note: The hoses and the condernser were also replaced along with the compressor and other parts listed.

[@samersarah957]

Thank you so much professor Scott for your videos with good illustration I saw 4 videos from your channel and I’m really appreciate all these information but I can’t find more videos. Question:What prefer to use for flushing whole system? Q2:What kind of gas use to pressure the whole system and how many PSIG? Q3:How many inches of water column go down to pull moisture from the system?Thank you again.

[@juanr3421]

I was wondering if a vov can be used on a system that use a capillary valve in conjunction like the one on the trailblazer ext ( that has 2 evaporator, one in front and the second for the rear)? Thanks!

[@filibertovalero653]

Thank you professor quick question , if you have a fot system which is short cycling , and when you touch the line before the evaporator is cold but when comes out to the accumulator is warm is that an indication of low charge or leak on the accumulator? Thank you

[@ProfessorPentane]

You are correct, this is probably an undercharged condition.

[@rogerd8121]

So I have a 04 super duty 6.0 diesel and had all new a/c system,why would the evaporator core and the lines coming out would ice over?

[@920PC]

Thank you for the great animation and explanation! Question: It looks like I can buy a fixed orifice valve OR a variable orifice valve option for my 2003 Chevy Silverado. Is there any reason I should not "upgrade" to a VOV? Is this accurate that I can just pop in a VOV over a standard one without adjusting anything else in the system (Assuming a clean and operational system and a proper flush, evacuation, and recharge after the swap). Thank you

[@ProfessorPentane]

Hi Kyle, Yes, you can put in the VOV if designed for that vehicle. I would only do it if you already have the system apart and was planning on replacing the FOT anyway. If will give you a little bit better cooling in that stop and go city driving. Good luck!

[@920PC]

@@ProfessorPentane I do have the system apart at the moment. Do you happen to know the proper part number for an AC Delco (if they make it) VOV? Thank you

[@sideburns2009]

@@920PC acdelco 1550121

[@scooch3500]

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?

[@ProfessorPentane]

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