How much PSI on the a/c system???

Discussion in 'Gen 3 Prius Technical Discussion' started by Saul Sanchez, Jul 15, 2020.

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  1. Saul Sanchez

    Saul Sanchez New Member

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    So it's pretty hot out and the A/C is never cold to the point of ever turning it down, it's just pleasant anything above Lo temperature and high fan speed is not enough, how much PSI should be on the low side???
     
  2. PriusCamper

    PriusCamper Senior Member

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    The system is variable pressure, so if you don't know what you're doing and don't have the right equipment you're going to kill your compressor, which is expensive. Read up on everything @lech auto air conditionin has posted on here if you want to learn how to do it right!
     
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  3. Grit

    Grit Senior Member

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    You work for lech auto!!!
     
  4. PriusCamper

    PriusCamper Senior Member

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    Not only do I NOT work for him... I could never afford him... If you want to ruin your A/C system and have expensive repairs, don't learn from him.
     
  5. lech auto air conditionin

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    Lol that’s funny

    speaking of Prius it just got another dead Prius compressor today it was only charge 280 g long ran low on refrigerant for a long time overheating winding it self to death. But the pressures look good before It’s burnt up
     
  6. lech auto air conditionin

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    It does not go by pressure it goes by weight do you recover all the refrigerant and it gets laid back in my factory specification only.

    But every manufacture does have a specification in the AC part of the repair manual for a specific vehicle that gives rough estimate pressures. They have very specific operating conditions you must set the vehicle in first before looking at the pressures to get even close to accurate.

    One very important aspect to learn and understand is that the smaller the refrigerant capacity and a higher efficiency of the system is the more sensitive it is too small or big changes in refrigerant charge much more crucial. Remember these systems are only 12 ounces to 15 ounces of refrigerant. If you’re two or 3 ounces off that’s a big percentage of the entire system charge.

    Unlike the old Buick’s Fords and Chrysler’s of the 70s and the 80s that had large iron 30 pound compressors with slow revving engines and condensers that were 36 inches long 26 inches high and an inch and a half thick. With refrigerant charge quantities starting at about 2 1/2 pounds to 3 3/4 pounds if you put two or 3 ounces too much or too little it did not even know it it’s like shooting an elephant with a BB gun.

    This is why I am constantly seeing burnt up Prius compressors that have just been previously serviced by technicians who have 20 to 40 years experience they apply all their years of experience of old large antique systems to a Prius and they give out information and recommendations based on their past knowledge of old antiquated systems before electric compressors were ever even installed on a vehicle.
    So remember it’s really simple first drain system 100% second evacuate system for a very long time to a very low vacuum reading third fuel system by weight only to the factory specified label and you can’t go wrong
     
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  7. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Or even simpler: head for dealership. Around $150 should do it.
     
  8. 2012 Prius v wagon 3

    2012 Prius v wagon 3 Active Member

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    I put some info copied from the 2010 service manual in the following post:
    Air conditioning | PriusChat
    More info there, but the short answer is, while running under controlled conditions, with TechStream:

    Standard Pressure: Low pressure side: 21.3 to 35.6 psi

    The manual literally has about 1000 pages related to Air Conditioning. Most of it is other stuff obviously, like the AC neural network control system (LOL) or amplifier. WAY more complicated than a traditional car AC that is mostly mechanical. These are of course still mechanical (thermodynamic) at the core, with R-134a, high/low-side pressure, etc. but have a ship ton more electrical controls crap wrapped around them.

    So it makes sense to be cautious, but that is the pressure range specified by the manual. Of course check for codes first, etc. and proceed cautiously. I'll also add that non-Prius systems would typically have the pressure range specified in a chart, with variability based on ambient temperature and humidity.
     

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  9. Ed Beaty

    Ed Beaty Active Member

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    "Or even simpler: head for dealership. Around $150 should do it."

    Agreed. Or even better: I just found a local independent garage (even close by me) here in SLC that works on hybrids and had them touch up my A/C.

    $147.00 total. Very satisfied, and HAPPY to've found them.
     
  10. lech auto air conditionin

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    And like all books and manuals test were performed under ideal conditions laboratory conditions, similar but not always the same in real world conditions.

    And none of the pressures are temperatures will be accurate if you have a clogged neglected cabin air filter. You may be trying to fill up the system reading your pressures but your pressures are absolutely false. Because of a restricted cabin filter Lauren the heat load over your evaporator giving you false readings.

    Then there’s a narrow window situation as your refrigerant level gets low on some compressors The high side pressure normally goes down but there’s a super crucial critical point where the lack of oil return and refrigerator cooling costs the compressor to superheat and add heat and pressure to the high side the high side falsely skyrockets but but yet your refrigerant level is actually very low. This is never accounted for in any of the OEM service manuals.

    AC PRO fanboys, now this product is in a classification of its own and your pressure readings will mean absolutely nothing when you come across this scenario. Prius AC system refrigerant capacity 420 g , Compressor refrigerant oil lubricant capacity 2.75 ounces. The car has a slow refrigerant leak and the customer or the shop they have been going to keep stopping off the vehicle with a can of AC PRO. AC PRO contains 3 ounces of a solid liquid oil and supposedly super duty NASA approve miracle wonder drug that makes your system colder lol . Now as you deplete your bottle of AC PRO You have just doubled the capacity of a solid that does not like to be compressed in your air conditioning system. And in the tiny passages of the high-efficiency micro channel evaporator coats the inside of the tubes and displaces the refrigerant and acts as a insulator. The readings will not correlate and me nothing from the factories manual. But the person trying to interpolate and diagnose by the readings out of the manual will be led down a false path with expensive repair results.

    Then there are the guys with air-conditioning machines who are cheap ignorant lazy and do not own a refrigerant identifier. They pull in every Tom Dick and Harry’s refrigerant out of different customers cars we are son of them have been contaminated by other refrigerants high percentages of air massive moisture contamination and it goes right down inside their machine to mix with all the refrigerant. Then they take their hose out and stick it down the hole of your innocent little Prius and blow off a load of contaminated refrigerant spreading that infection like an STD. This gives you different pressure readings that are not calculated for in the manual that’s giving you a false diagnostic reading to try to judge by.

    This is the real world.

     
  11. 2012 Prius v wagon 3

    2012 Prius v wagon 3 Active Member

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    LOL. Great info.

    I always laugh when I see additions to a pure commodity product like R-134a just to distinguish it from it's competitors, yet it almost certainly makes it worse. Marketing vs. engineering. One of those times when I'd prefer they were actually lying about the improvements and it was just pure R-134a.

    On the refrigerant STD dissemination :ROFLMAO:, I've always wondered about that. What is the solution? Do amazing machines exist that can purify whatever gets extracted, dispose of the old stuff (leak stop, dye, magic stuff, wear particles, wrong oil, etc.? Or do they just use some special AC recovery condoms?
     
  12. Grit

    Grit Senior Member

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    Someone gives you great info, first reaction is to laugh at it.
     
  13. lech auto air conditionin

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    Yes with this refrigerant STD pandemic going on we must pass out giant condoms to all the shops the first place we bought them is over the heads of the owners of the shops of course with no breathing holes.

    The standard machines and Automotive do separate the solids from the gases so they are capable of removing the oils and other additives. Unfortunately some of the leak sealant caused problems with some of the refrigerant recovery machines some leak sealants turn into a solid and destroy the machine that’s a costly mistake. Some sealants when the customer car gets in the front and Accident goes to a body shop they remove the condenser leave the lines exposed to the atmosphere for a week or more while they’re waiting for parts that oxygen and moisture gets inside and makes a nice thick gooey molasses. Bet you nobody thought of that problem Bet you nobody thought of that problemlol .

    Severely contaminated refrigerant depends which blend of refrigerant it is they can be sent back there’s places that pick up contaminated or fresh refrigerant and just like distilling and cracking crude oil into gasoline and other solvents they do the exact same with refrigerant to purify it. Unfortunately some blends cannot be separated or not worth it they must destroy them incineration unfortunately is one of the methods and it puts other very nasty chemicals up into the atmosphere because of the certain individuals who are too cheap to lazy too ignorant to buy a refrigerant analyzer. And go stick their dirty hose in a dirty hole and spread that refrigerant STD around.

    I’m starting to see brand new vehicles with R1234YF contaminated with refrigerant STD pandemic explosion. Just got a love those cheap lazy ignorant shop owners who can’t even work or diagnose their way out of a wet paper bag for spreading the love in around.
     
  14. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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    Would removing cabin filter mess things up too? Seems like a good "leveller".
     
  15. ChapmanF

    ChapmanF Senior Member

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    Keep your cabin filter on, this is a family forum.
     
  16. lech auto air conditionin

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    Removing the cabin filter would be an excellent way of plugging up your evaporator and costing you several hundred dollars for them to spend seven hours removing the dash to take apart the HVAC box to replace it.
     
  17. Mendel Leisk

    Mendel Leisk Sunday driver DIY’r

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  18. ChapmanF

    ChapmanF Senior Member

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    My old Bronco II had no concept of "cabin filter". It had a blower that would suck dry leaves in through the cowl, pulverize them into fine leaf debris, and pack that evenly into the evaporator. The more obstructed the evaporator got, the longer the leaves spent in processing, they got pulverized even finer and packed in the gaps between the coarser leaf bits. Over the years, eventually turned it into a brick.

    I ended up setting that evaporator (with the tube ends plugged) in a wastebasket filled with tepid water and some of those microbes/enzymes you buy at the hardware store to keep a septic system healthy. After soaking a few days, took it to the coin-op car wash and pressure-washed the digested leaf goo out of the fins. Sparkly clean, no damage to the aluminum from the microbes.
     
  19. lech auto air conditionin

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    The leaf mulch acted as a organic biodegradable cabin air filter The leaf mulch acted as a organic biodegradable cabin air filter
     
  20. Leadfoot J. McCoalroller

    Leadfoot J. McCoalroller Senior Member

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    And best of all, the evaporator (probably) just unscrewed from its fitting with one hand reached under the dash. Heck you could probably do it while driving.

    Okay I know it couldn't have been that easy, but... I'm guessing it wasn't as gnarly as prius evaporator access.
     
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