How To Recharge an A/C System Professionally DIY

Mountain 8205 R-134a Manifold Gauge Set: amzn.to/2LSDhXu
A/C refrigerant can tap: amzn.to/2OITwEg
U/V flashlight & UV blocking safety glasses (protect your eyes!): amzn.to/2nbWKnb
If your A/C isn't blowing as cold as it used you, some of your refrigerant has probably leaked out due to a leaky schrader valve in one of the service ports. In this video I will show you how to inject ultraviolet dye into the system to check for leaks, as well as how to use a manifold gauge set and vacuum pump to refill your system with refrigerant.
If there is still refrigerant in your system, you will need to have it evacuated by a shop with a refrigerant recovery machine before you can perform any repairs such as replacing schrader valves or o-rings or any other component.
You can buy UV dye and a UV flash light at any automotive parts store. Remember to use UV protection when using the flash light.
When recharging your system, you should put in the amount of refrigerant that is recommended by the vehicle's manufacturer. There is usually a sticker under the hood telling you how much you need to put in.
In the case where you don't have a sticker, you can go by the pressures displayed on your gauge set. The following chart should help you to figure out the proper pressures for your vehicle:
R134a Pressure-Temperature Chart
Ambient Humidity Low-side High-Side
Temp PSI PSI
70 Low 25 to 30 140 to 190
High 28 to 35 165 to 220
80 Low 26 to 33 150 to 200
High 30 to 36 190 to 260
90 Low 31 to 37 170 to 220
High 37 to 45 210 to 290
100 Low 35 to 44 195 to 245
High 38 to 48 230 to 320
110 Low 40 to 50 235 to 285
High 42 to 52 260 to 350

[@TOY35MPG]

It’s been 4 years since the video so I am sure you have figured it out but there is a way to avoid losing refrigerant when disconnecting the can. Close the can valve first. The compressor will pump out the yellow line. Then close the low pressure valve.

[@wlondoner]

The most comprehensive video for DIYers. Fantastic job. Thank you for sharing it with us.

[@angelf9800]

Question How do you know if you need any oil in your coolant system?

[@thomasdement7885]

Very helpful. Most comprehensive video on these issues I've seen.

[@kenc4104]

Mistakes or not, I appreciate your careful explanation of the steps to take. Took care of my truck today following your lead. Thanks very much!

[@50sKid]

Thanks. There are always critics on the internet.

[@melplishka-se8bf]

If you have air you have too evac and recharge.

[@chucklemberg4968]

@@melplishka-se8bf His video states this!

[@robertcowles7191]

Excellent!!! I watched tons of vids on this being a newbie never done a/c on my truck. You filled the gaps of what the others do not include. Such as 1. how the manifold valve knobs control the flow 2. leaks 3. new can adapter. Thank you!

[@EducatedVarangian]

totally appriciate you taking the time to make this video brother.

[@andresantongiorgi860]

Thanks 50's kid. I see that I need a lot more tools. Explaining the laws on how to and how not to dispose of refrigerant saved me a fat ticket or a one way trip on the grey goose shackled from head to toe. You took no shortcuts and you cut all the none informative mumbo jumbo which leads me to believe that you did it primarily as an informative video and not to become a contestant on dancing with stars. Good job. I got to go to the hardware store before I single handedly fry all of the world's electrical components or faces. You da man. I'm subscribing.

[@sheri1983]

Man! I'm watching hundreds of videos on AC repair and this is the best one! I ordered the same manifold gauge so it was helpful to see it in action, also I want to add uv dye. Thank you so much!

[@tc96z1]

I had the manifold setup to replace a condenser two years ago. The steps to top off a system are very different than pulling a vacuum first on a complete system evacuation. This is the only video I could find that explains ‘manifold functionality’ clearly. I went out and topped off my Accord in about 15 minutes. I actually purged the all three hoses with the Freon can attached to the yellow delivery line before hookups to the system. After closing the Freon can valve and both manifold valves I attached the manifold system to get readings. Then opened the Freon valve before opening blue low side periodically and bumped the High side to about 250. Closed the can off and held it above the manifold using gravity to help drain the the yellow charging line...... Like 👍 a Boss. Really, again, you did a great job taking all the mystery out of the manifold functionality.

[@peterschweizer659]

Very good presentation! You explained the reasons how, why n when the steps are preformed. I find that most You tube Videos' do not cover topics as well as you did. GREAT JOB! I forwarded this to my son so he can see what I was telling him as to how to fis his cars AC. From a retired Aircraft, auto, RV mechanic and instructor.

[@guygoodine5255]

Great video. Great refresher. Very knowledgeable and professional presentation. Acts and sounds like he knows his stuff! Good job.

[@richardroy5437]

This was the best video on charging and helped me!! I had questions about vacuum with oil in the systems, and bleeding air and this video answered all of them. Very informative and easy to follow and listen to. Thanks!

[@kdeh21803]

Did you have a scale so you would know exactly how much refrigerant was put back into the system?

[@richardroy5437]

@@kdeh21803 Yes. Made sure can was on liquid side, and measured amount by weight.

[@kdeh21803]

@@richardroy5437 that would be great if the system was completely empty but never just top off.

[@richardroy5437]

@@kdeh21803 Mine was completely empty. Pipe broke at flare joint, system was at 0 psi. I replaced lineset, vacuumed it etc, and refilled by weight. I was worried about compressor oil since there was oily residue where it broke.

[@kdeh21803]

@@richardroy5437 Then you replaced the amount of refrigerant on the sticker..... a few weeks ago I repaired a system on a very small vehicle and the sticker said the maximum charge amount was 16 ounces.... I got to thinking some of these "top off" cans are more than that and people with no training in car AC work get these cans and empty them into their car thinking their doing something, "Great" and they have put 1/2 pound more refrigerant in their system than it calls for and it really does more harm than good. Because a can says, "AC Pro" does not make you a pro. AND some of these cans have a "low pressure" hose but I've never seen one with a "High Pressure" hose..... you need to guage both.

[@bignappy504]

My 01 sport trac a/c is finally needing some attention. I'm getting my parts list together right now. I'll let you know what happens soon. Thanks for sharing.

[@Dr2009king]

You are my man, i'm happy to see someone knows what's going on behind the seen ( on those manifold gauges ) ... most of my friends believe that the 2 valves controls the high and the low lines .. and they call themselves professionals :D, tried many times explaining to them that the valves are used to control the connection between the low - high & the yellow .. but they don't seem to get it .

[@benfried3745]

Very good explanations here. Have watched several videos on recharging AC systems, and this one is great. Thanks!

[@rhomel2023]

You are awesome mister, I thank you very much for tons of info, makes me equip by doing DIY on my car ac system.😍

[@hubercats]

Excellent video, and as you point out near the end, an R135-specific gas temperature/pressure chart will allow people to take into account the ambient temperature. In fact, if you connect the gauges and read the pressures BEFORE starting the car in the morning, both high and low pressures will be nearly equal (they will have equalized over night) and will reflect the outside morning air temperature. If the pressures are not close to one another it likely means there is an obstruction or defective component in the system. This is valuable information in and of itself and trivial to obtain. I have to say that I’m surprised at how few videos even mention using the gas temp/pressure chart as it’s very easy to use and highly informative. Thanks again!

[@davewilson4826]

Good tutorial to brush up on my skills. Thanks for sharing!

[@hoffy628]

Best video I have come across, you hit all the points the other videos were missing thank you

[@CraigArndt]

Great video and explanation of the manifold. Sure a scale is best and all that stuff, but you can really get close with a professional set of gauges just as you showed.

[@darrylhowe1465]

You might be "in the ball park" without a scale; however, it is not likely you would be close and highly unlikely that you would get "really close". Use a scale!

[@chuckmac6541]

Thank you very much for your video it was very helpful because I was about to return my gauges because I did not know when you hook up your AC unit your gauges will move and you have answered the question please keep up the videos

[@Sroor2023]

Thanks 👍👍👍 what you mentioned is a common mistake that most people diyer when changing can they didnt close the blue line 😂 and they think they have done it right 😁

[@illbebad]

sure wish I had seen this video before! Must have watched 50+ videos over a week or so, NONE mentioned the adapter you need for cans if you have an older gauge system. and few mentioned to only open the right (high pressure) for vacuuming only. Other easy to understand instructions, the chart for pressure at the end, etc. Many thanks!

[@jotu173]

Very good video. I appreciate the energy and detail. Respectfully said (though) I realize that you can SLOWLY sort of shake the can (as you did) but most all sources say to avoid (if at all possible) doing that as it may allow liquid to hurt the compressor (when can is upside down). Doing so will fill the system faster, but increases potential of harming it. Just some general info & food for thought.

[@JustChuck]

I agree with you that liquid hitting the compressor is a bad thing. I like to use a large bowl of hot water to put the can into. Even when 90% empty and mostly floating in the bowl, the hot water helps the head pressure in the can.

[@sflotr]

Always wanted to know how to do this. Thank you!

[@mrau92me]

Great video that many mechanics probably don't want many to see. Only thing is that once you open the system by removing the Schrader valves, run the vacuum pump on it for at least 30 min.

[@simplehermit]

Excellent instruction. Thank You.

[@vincentbarkley9121]

Excellent video. Thank you.

[@rickmayfield4930]

Awesome video. Thank you for making it.

[@scottjones1491]

This is by far the best video I have seen regarding recharging an AC unit thank you very much you could not have done any better

[@briand4000]

that was GREAT. Thank you!

[@facesmasher4216]

great demo 🏆 thanks boss 👈

[@jimbola77]

very nice video thank's for sharing!!!

[@jacquelineMeyers-is1zz]

Awesome job ! Finally gettbe picture of the system. I have spent over a tbousand dollars and after 2 months, no ac again, now the compressor has seized . Nothing intbe repairs was replaced, but the guy said the pressure was very very high, but only just now found out about the expansion / TXV valve, which was probably what was wrong in the beginning, now the whole system is compromised. On a small SS income, Argh, this hurts. Its a 99 Ford Expedition , otherwise very sound condition. Thank you again.

[@tcorrellii]

Thank you. Great video!

[@technovan1133]

thank you for video very helpful, i m about to do in my Mercedes !

[@chrismasila3414]

Very informative video for beginners. Good work .

[@meldrake1623]

Super camera job!

[@brentbradley6711]

Yep no reflections etc.

[@mrd.808]

I would pressurize the blue line prior to hooking up the low side valve. Other than that, I didn't catch anything out of step. Awesome youtube channel, I appreciate you sharing.

[@osmangoniyes2504]

Good work bather

[@johnsonlong1272]

You probably already know this by now. The valve you screwed on the can adapter should be a back seat in front seat valve meaning if you screw the valve all the way in to seat it is shut off or if you screw the valve all the way out to seat it is shut off.And refrigerant only flows when you're in the Midway point. If your valve does not work that way get yourself a front seat back seat valve that way you can backseat the valve and change the can without losing refrigerant from your line also not introducing air into your line. Very good video though you did a nice job of explaining it as well as including an ambient pressure chart.

[@SvcGlobal]

Great video, thanks.

[@mckoylach1622]

Great video,thanks

[@1966jalopy]

I pulled vacuum on car last night and was going to check in the morning to see if it lost any pressure. I then thought to close the valves to check if manifold gauge would hold pressure. This morning, gauge at 25 instead of 30. Opened valves, system was still at 30. Glad I checked this way.

[@chuckm869]

Awsome video. I have to recharge my system and great to see detailed how too 😊

[@tankeryankercruz7795]

Thank you.

[@ginginthing]

Great video. Thx so much.

[@dionybarte9087]

thank you soo much i appriciate your video

[@IIGBII]

Awesome Video Mate

[@cesarmiranda2205]

Awesome vídeo, very nice hints, you bet...

[@northpoint1039]

Hi, You made a great video here. Thank you very much. I don't own a BMW which most of your video's seem to be about. I have a GM. However, A lot of your videos are very helpful though. This one is spot on :) I'm subscribing!

[@bigjon.6258]

Great info Brotha...

[@tudocervera3764]

nice video my friend... very well explained..

[@newageguitar]

Superbly informative pro video, thank you. Answered a myriad of questions..now I know thanks to you..:))))

[@yahyaamiri7263]

i am iranian and thank you for your video.

[@domingohernandez4189]

good job👍

[@missing1person]

car work is so relaxing.

[@jimmypatterson9854]

No... It isn't.

[@missing1person]

@@jimmypatterson9854 ok

[@physiqueandstyle]

Best video, actually shows the behavior of the gauges from beginning to end.

[@fpamps5805]

Thank you!!!

[@jayt6215]

Super helpful. Thank you!

[@carloscepeda7462]

thanks for this video awesome

[@timmygilbert1371]

Great video !

[@hg2.]

Well done. Thanks.

[@heavyflippingrandmasboifir669]

Bro you brought this video right on time. I have a Caprice classic ‘96 and I want to know what the standard operating pressures should be? Thanks in advance

[@BuscandoSanaDoctrina]

The vacuum contamine the admospher?

[@kevinwatson9405]

No, it don't - vacuum goes straight up, back into space...

[@brentbradley6711]

This is the best AC video I have seen so far and I was a mechanic !

[@YourMom-mq4zc]

You should keep that to yourself or add I tried to be a mechanic once but I sucked at it ;)

[@brentbradley6711]

@@YourMom-mq4zc Beats a wannabe like you

[@YourMom-mq4zc]

Yes that's why he's the pro with the 12 oz can and I have 30 lb bottles and a very expensive scale also he's not taking questions so i get to answer so idiots like yourself don't kill themselves trying to save 30 buck or screwed by a video watching use to be

[@brentbradley6711]

@@YourMom-mq4zc Wow, I'll have to swing by and get your autograph.

[@kevinwatson9405]

@@YourMom-mq4zc Any assminded ape can buy equipment. He shows the difference by actually knowing how to do it right, and the consideration of telling other people how to do it. I'll bet they called you "three strikes Mike' because you never did a job that didn't come back at least twice before they gave it over to a competent mechanic to do it right.

[@yabasvlog3439]

Great job

[@umaribrahim1799]

Thanks great video

[@robertodebeers2551]

Good job!! Thanks.

[@androwjhone421]

Very nice explanation... am gonna right now subscribe your channel... wish you all best ...

[@patagualianmostly7437]

Inverting the can of refrigerant charges the system in the liquid phase. In theory, this liquid could reach the compressor inlet reed valves and damage them. In practice, the liquid should "become" gas (due to the lower pressure in the lines between the can & the Compressor inlet...) But do bear it in mind.... do not blindly flood the lines with the refrigerant in the liquid state. There is a lot more to consider in theory than is explained here. Consider this as rudimentary first-aid at best.

[@ernestsupergmailcom]

actually back in the day ,the 90s when certifications were required to handle r12 and conversion kits were introduced ,that mineral oil in r12 was not compatible with the new pags,you would have to change the drier and flush the system completely,then add your new pag which is the oil after you vacuumed the system 6 ounces was the usual a tech would measure 6 ounces and stick the yellow hose into the oil open the low side valve and it would be sucked in and then you would charge the system.the conversion kit as i remember were only two quick disconnect vavles that screwed over the existing r12 valves.and back then brake fluid was used to flush the system.

[@50sKid]

Sounds right to me

[@jimmyraythomason1]

Back then R11 was the flush.

[@AR3n3gad3]

Thanks so much!

[@displayfireworks1]

14:29 is all most of us need to know

[@Simon-fm8yc]

Lucky for me that my boy is a refrigeration and AC engineer and he can do mine!

[@Dat550go]

Can he do mines too?

[@mikethomas5523]

very good video

[@nrabines]

Cool video , can u some on home a/c's. Thanks.

[@davidthomas4697]

Thanks

[@daviddavis9411]

Good work

[@peenopiani7209]

Hi dear sir:excelent teaching and prophesional,thanks. Yours sincerly:peeno

[@stanfordgordon2167]

sir i love your vidio hands down

[@johndumas4467]

Hey 50sKid... love all your vids. If I let all the r134a out of my system and vac it out, will I need to replace the oil. I'm handicapped and trying not to have to pull the compressor to dump the oil and refill. Thank you for your time. Johnny

[@cyberkiller83]

If i looat at minute 07:13 i can see clearly that the lowe side vacum changed a little bit. Definitly some pressure enter back to the system on those t wo hours span, so i think you still have a leak. Regarding initial charge, there is two way to do it. The way you just did it's called, gas state charge, that is, in low wide open and gas can upwards, so you are filling with gas. and the other way is liquid state charge, in this way, you (WITH THE AC OFF) open only the high side valve and you turn over the R134A can, so you are injecting high pressure liquid to the system. In a perfect scenario, YOU DONT TURN OVER THE R134A can in a low side charge, because you are inyecting LIQUID TO THE COMPRESSOR and that can bend the pistons, it COULD happend, so its not very safe, to the compressor you can only deliver GAS! so you CANT TURN OVER THE CAN. After all the first R134A is gone, you close the high side valve and charge the second can in gas state charge by the low side. I do this high side charge because the initial can charges much faster this way.

[@ariankojefferson2758]

Perfect

[@sterlynali6679]

Good video

[@50sKid]

Thanks!

[@kapalselam8777]

The most accurate solution in charging the hvac system is by measuring in weight,because the refregirant enthalpy will diff depending on your altitude from the sea level

[@chucklemberg4968]

OK, here's my problem. I went to recharge the system. Things were going very well; but then the high-pressure line on my manifold gauge set burst and started venting from the high side. I now have the better portion of a can in the system, but I'm not sure how much. I do not wish to pay for an evacuation and start from scratch pulling a vacuum, checking for leaks, then adding refrigerant. Right now, I'm just planning to add more refrigerant until the manifold gauges reflect the high side of the pressure range set out for the ambient temperature and humidity. What would you recommend?

[@megadeth1763]

This must be the only set of gauges he has (not really) it doesn't take but the $14.99 set or single gauge you see that's already attached to a large bottle of 134 you bought 20 years back, which is a rip off but for ppl in a hurry or do it yourself ERS it's a good time as long as you know what you're doing. Don't over charge or you may blow the compressor. There's a good cleaner that is excellent for spraying into and through the fins of the condenser then after just a few minutes spray the cleaner with clean water from a garden hose, if you have access to the condenser look to see that the aluminum fins are straight, you may find there's a tool to help but it's a slow process but the better transfer the cooler your AC so that's your choice. Stay Cool n Stay Happy !

[@Showmethefish]

Pulling a vacuum completes two things...# 1 it detects a leak # 2 when you pull a vacuum down below barometric pressure the air becomes hot enough to evaporate any moisture that's in it...

[@StonecrusherinPCB]

Awesome video thanks. Also to note you show how to bleed the yellow hose when adding a can of refrigerant! Great Job!!! This was very helpful!

[@darrylhowe1465]

HINT: Turn the can upside down. That insures "liquid" flows up the yellow line and when the liquid reaches the top, it creates a visible mist. Then there is no question if you have the line purged. If you have the can upside right, only the gas escapes and you can't see the gas. NOTE: It is highly unlikely his system is at the correct charge. The only way to properly charge an A/C system is by precise weight.

[@chucklemberg4968]

@@darrylhowe1465 "If you have the can upside right, only the gas escapes and you can't see the gas." That has not been my experience. The refrigerant gas has a clearly different appearance from the plain air that is in the line once it enters the atmosphere. AND, pulling liquid into the compressor can lead to compressor damage.

[@darrylhowe1465]

@@chucklemberg4968 I don't doubt that one might (in some cases) be able to see the difference in light diffraction due to the temperature difference between R134a and the surrounding air; however, R134a is colorless. (Source: en.wikipedia.org/wiki/1,1,1,2-Tetrafluoroethane)

[@chrisv4640]

Most cars have UV dye in them from the factory...It says so right one the charging weight sticker under the hood....

[@user-ew6dp7eo7g]

GOOOD

[@joeynenj]

Great video. Wondering if you can tell me if 36psi on the low side and 175 on the high side at idle with a ambient outside temp of 63F is ok for a 2010 scion xb. I would appreciate it. Thank you again for the great video.

[@chucklemberg4968]

I usually coat my valve cores and o-rings with PAG oil. I was wondering, since you just installed them without any, did you experience any subsequent leaks?

[@titolongo1]

Excellent, tks. 🇵🇦👍👍👍

[@boztech]

Great video!!! Bought one of these manifold gauges and never used one. My A/C never gets very cold. Tried a can with an included gauge. Said pressure was a bit on the high side. If I drive down the highway it gets a little colder, but still doesn't work good. Any ideas???

[@jm1272jm]

Very nice job there 50sKid. Learned a lot. I have always been curious as how to bleed the actual low/hi hoses AFTER service is completed. When disconnecting low/hi couplers from car, the manifold gauges are still reading pressures. How do you zero them out once off the car?

[@50sKid]

With all the valves closed on the manifold, if you leave the yellow line connected to your can (with the tap closed) and the low line connected to the car and open, you can disconnect the high line (the gauge still shows pressure and nothing is leaking out of the high line, indicating there is pressure in the high line), you then just open the high valve which allows the contents inside that hose to travel into the low hose, and then you can open the low hose valve at the manifold and let everything get sucked into the car. When you close everything off you are then left with about 30psi on both sides of the manifold because all the pressures got equilized. Then disconnect and you can let whatever is in the low line vent to atmosphere because you basically have no way to recover it. It's a tiny amount.

[@jekinneys]

Draining the oil. A lot of compressors actually have a drain plug for getting oil out. If it's been more then 5 years and your system is empty, it's a good idea to change the oil. Any time your system is empty for what ever reason it's a good idea to change the accumulator and filter. Any good shop that services your A/C will evacuate the system, change the filter and service it back up charging you ONLY for what refrigerant it required to top off. The machine will recycle/re-use the refrigerant.

[@chadriddle3517]

Like a boss!!

[@Bwanar1]

You should always confirm the leak, before just replacing a part. Easiest, was to check your schrader valves is to spray soapy water mix on them. No high tech equipment needed.

[@chucklemberg4968]

UNLESS your system has ZERO charge in it to begin with.

[@Bwanar1]

@@chucklemberg4968 of course one of the first things you would have done troubleshooting the issue was throw a set of gauges on it.

[@Mandinka711]

My AC wasn't blowing very cold and would only kick in that not very cold air after about ten minutes of driving in hot weather (90 deg). The clutch is engaged the whole time the AC is on. I vacuumed the system and only got a vacuum of 15 (or is that -15). I let it sit for 45 minutes and the vacuum didn't change. I then put a 20 oz can of refrigerant in (its an Audi A3 which I believe takes 19.6 ounces) and the air was colder (but it's only 75 degrees outside now). The hi pressure was up to about 150 on the manifold gauge and the low was about 40 on the gauge on the can (couldn't fill using the gauge set because I didn't have the right fittings). The air was noticably colder and the AC pipes were cold to touch the low and warm on the high, not hot but definitely warm. I then disconnected everything and let it run for a few minutes then re-connected the gauge set on both high and low. The high now read 125 and the low was 0. So I disconnected the low and connected the gauge from the can (having removed it from the can itself) and it read 40. I tried again and the gauge set (low) still reads 0. The can gauge still reads 40 when I reconnect it only now the high reads 100. I couldn't look for leaks because my refrigerant doesn't have dye, I have to rely on the vacuum not changing proving there are no leaks. Am I doing something fundamentally wrong ? Have the gauges suddenly malfunctioned giving the 0 reading on the low when the can gauge reads 40 ? All the time I had the engine running with the AC on full and I also noticed that the radiator fans were going into overdrive every few seconds. Another thing I tried was hooking up the gauges and opening up the low at the gauge set manifold to see if any pressure came out, none did even with both low valves wide open. Assuming there is an issue with the low on the gauge set why is my high only 100 when the can gauge reads 40 ? Compressor, orifice valve ? If the gauge set is not malfunctioning (it seemed ok until half way through this process) then what's going on, how is one gauge connected to the low reading 0 and a different gauge connected to the same port reading 40 ? Hope you can offer some suggestions. I'm at a loss.

[@50sKid]

Umm, it's concerning that you only got -15 when doing your vacuum. It should have been close to -28" of mercury... basically pretty darn close the maximum vacuum on your gauge. Definitely sounds like something is wrong with your low gauge on your manifold set. I think using the gauge from the can for that is perfectly fine. When you said you tried to let some pressure out with your manifold, you said none came out with "both low valves wide open" -- what did you mean by that? There is only 1 low gauge. The reason your high is 100 and the gauge on your can is 40 is because the high is reading from the high pressure side of the system and the low (can) is reading from the low pressure side, so obviously there should be two different pressures right? I'm concerned that you only have 100-150 on your high side. It does sound you might not have enough refrigerant in the system. Double check the sticker under your hood to see the correct amount that you need.

[@Mandinka711]

When I said "both low valves wide open" I meant the low valve connected to the low pipe on the AC system as well as the corresponding valve on the gauge set (poor terminology on my part). Both were open but nothing came out which indicates to me that the system was empty, however, when I disconnected the gauge set and just used a gauge from a can connected to the low on the AC system it read 40 psi. Also, the air blows colder than ambient so I'm assuming there is some function at least. Autozone looked up the car and they told me the system required 19.6 ounces of refrigerant so I used a 20 ounce can. I'll see if I can find out more. Would a 15" vacuum be strong enough to expose a leak if there were one ? The vacuum pump oil sight glass indicated that it was low on oil, would that cause poor vacuuming performance from the pump ? Should I top off the oil and try again ? If I only pull a 15" vacuum then do I still have residual air pressure in the system which uses up refrigerant "space" therefore causing low refrigerant because half the space is air and half refrigerant when I fill it ? Thanks

[@davecc0000]

+Will Beames "...the low valve connected to the low pipe". This should be turned clockwise (we usually think of turning counter-clockwise to open a valve) and the one at the gauge should be turned counter-clockwise. Might that be your problem?