AC only cold when manually running compressor @ 7K RPM

Discussion in 'Gen 3 Prius Technical Discussion' started by BeautifulPacificNW, Jun 3, 2019.

  1. BeautifulPacificNW

    BeautifulPacificNW New Member

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    2012 Prius
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    I have a pretty good understanding of the AC system, so please don't ask me to check if the fans are rotating, or things like, is the AC switch on?

    Sept 2018
    : Noticed AC not performing well. Air was alternating between warm and cool while driving.
    October 2018: Took car to Toyota dealership for evac and leak test. System was vacumned out, Tech charged system with 1lb refrigerant, check the system the next day, and pumped out 0.8lbs refrigerant and report of low High pressure. They were unable to determing leak location, but suggested it is likely coming from back side of condenser, or from inside AC unit, (evaporator). (Paid $250 for attempted diagnosis).
    November 2018 - April 2019
    : Did not worry about fixing AC, due to drop in outside temperatures in the Pacific.
    Early May 2019: Warmer temperatures abound and decided to tackle AC issue.
    Mid May 2019: Took vehicle to hybrid vehicle specialist in Portland. Tech used camera and leak detecter and determined some amount of UV dye in the evaporator drain hose. Diagnosis determined as leaking evaporator/expansion valve. (Paid $130 for diagnosis).
    Late May 2019: Ordered replacement condenser from partsgeek along with replacement evaporator, expansion valve, and ND 11 compressor oil. I took apart the dash, replaced the evaporator, put in new expansion valve, and took out the front bumper and replaced ac condenser. I also replaced 12v accessory battery. Vacummed AC system to -29mm/HG for 1 hour, -vacuum pressure consistent. Put car back together and charged system with 1oz compressor oil, along with ~16oz R134a. High Pressure and Low pressure on manifold gauge looked good. AC was cool, (garage temp ~80F).
    Last week of May 2019: two day after charging system noticed that air was not cooling very well at the stop light. When car accelerated the AC cooling continued and vent air felt colder. Stopped car on side of road and verified both radiator fans working. Drove around town to make sure this was repeatable and this was the case. Ordered techstream and checked ECU's, there were no codes present in AC system or car at all. When AC on LOW with doors and windows open, the AC data reports target compressor speed of 4000rpm (actual 4000rpm, target evaporator themistor temp ~37F (actual 54F), AC regulator pressure sensor read 130psi. (High pressure sensor low??). Low pressure reading between 30psi and 45psi, added freon for about 60 seconds. No change on psi reading from AC regulator pressure sensor, low pressure barely budged. Waited 10 minutes with AC on LOW, door open. Manually accelerated compressor rpm with techstream to 7000rpm, AC regulator pressure sensor now reads ~185 psi, with ambient temp ~75F. Noticed immediately cold air from AC, NICE ICY COLD AIR. Cancelled active test, and system went back to normally requested compressor speed of ~4000RPM, noticed increasingly warm vent air and AC regulator pressure sensor went down to ~130psi.

    I already returned my manifold guage set to amazon because I wanted to buy a better quality model, which I have not yet done. Nonetheless if the AC regulator pressure sensor is reading high pressure line actual, then possibly no need for another manifold guage set. I have can of freon with guage on it to read low pressure psi.

    Is my compressor going bad? Why is AC system only requesting target compressor speed of ~4000RPM?
    (Compressor max speed is around 8000RPM in techstream active test).
    Is AC regulator pressure sensor a dependable source of High pressure line psi reading?
    Why is it when I increase compressor RPM to 7000rpm AC is frozen cold, with actual evaporator thermistor reading of 36F? When I let the system to run its requested parameters actual evaporator thermistor temps are between 45F and 55F, when target thermistor temp is 37F?

    Is my AC compressor supposed to be making normal High Pressure Line psi of 195psi - 225 psi (@ambient 90F) at the requested 4000RPM?

    When compressor speed was manually moved to 7000RPM I could feel it spinning through the floor boards of the vehicle. I have watched AC for over 1 hour with techstream, it is always requesting 4000RPM, is this the correct RPM request? It is always requesting the same Compressor speed I have never seen it changed. I just want to get the AC system back to ICY cold air, but I am confused by how this all goes together. I need to determine what. Can anyone check actual/requested AC compressor speed of their vehicle when AC on LOW. Maybe my compressor is supposed to make the 190 Psi when actual speed is 4000RPM, then that would mean my compressor is bad. I did not notice any metal fragments is AC when changing condenser or evaporator. I looked inside AC drier and no metal fragments there as well.

    Thanks for reading
    What should I do?
     
    #1 BeautifulPacificNW, Jun 3, 2019
    Last edited: Jun 3, 2019
  2. BeautifulPacificNW

    BeautifulPacificNW New Member

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    ***Update*** 6/3/19

    This evening afterwork I checked the AC system again. With current outside temperature at 73F. I turned on the AC on LOW with all doors open. Using techstream I measured the reported value of the high pressure line sensor, and psi was steady at ~140-150psi. Low pressure gauge adapter read ~35psi. Target Evaporator temperature read 37F and actual temp read ~43F. Target compressor speed and actual speed were both at 4000rpm. AC felt ICE COLD, and I ran it this way for a good 20 minutes. No major fluctuations. Then I drove it around and system stayed the same while driving.

    Here is an excerpt from the service manual.
    ----------------------------------------------------------------------------------------------------
    Read the manifold gauge pressure when the following conditions are met:
    1. Temperature at the air inlet with recirculate selected is 30 to 35°C (86 to 95°F).
    2. The blower speed is set to high.
    3. The temperature is set to max cool.
    4. The A/C switch is on.
    5. Doors are fully open.
    6. The power switch is on (READY).

    7. Normally functioning air conditioning system.
      Low Pressure: 0.15 to 0.25 MPa (1.5 to 2.5 kgf/cm2, 21 to 36 psi)
      High Pressure: 1.37 to 1.57 MPa (14 to 16 kgf/cm2, 199 to 228 psi)
    ----------------------------------------------------------------------------------------------------
    How is it possible that at 73F outdoors temp, the high pressure sensor is reading ~145psi when low pressure reads 35psi?
    The math just does not add up. I will monitor the system. Tomorrow has a high temperature of 76F, but it won't be until next week Monday that we will have a high forecast of 85F.
     
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  3. Asad khan

    Asad khan New Member

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    I had the same problem in my 3rd Gen. AC is not working in EV mode and on a lower RPM. Did u fix it?
    Please suggest any solutions?
     
  4. Maarten28

    Maarten28 Active Member

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    There should be no relation between AC function and EV mode. AC is electric and will work whenever the car is in ready, be it stationary, in EV mode or with the ICE on.
    I would guess that the AC not working at low speeds means there is too little cooling effect from the radiator. Could be related to the compressor malfunctioning.
     
  5. lech auto air conditionin

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    Caught my attention really fast when you said you added more Freon for 60 seconds. You do not charge air conditioning by time you do not charge air conditioning by pressures you do not charge air-conditioning looking at a site glass whether it is clear or Bubbley . You only charge by manufacturers specified weight using a very accurate scale Prius is her extremely sensitive to being two or 3 ounces overcharged or under charged.
    2: at that first leak attempt on a hard to find a leak I would have filled your system up with tracer line UV dye told you to take your car for about a week or two if it lasted that long run your air conditioning continuously whether it was hot cold snowing or raining and just adjust your fan in temperature leaving the AC button on all the time the purpose for this is to keep the refrigerant and oil with the dye constantly circulating to help find the leak.
    3: on average when it comes to air-conditioning I don’t trust the dealerships no matter which one they are at properly servicing air-conditioning on Prius is as far as I could throw their dealership building. This is speaking from experience Automotive air-conditioning is all I do from early morning till late night every day it’s my specialty for the last 27 years and fixing mistakes from the dealerships has become commonplace.
    4: on your oil charge I have a question you mentioned you replaced the condenser this has a recommended oil replacement charge of usually 40 mL . But you said you charged in 1 ounce of oil which is only 30 mL . On top of that you replace the evaporator which even loses some more oil but you did not compensate for that loss of oil. Where did you get your oil fill capacity’s information from or was it just guessing ?.
    5: so you used one of those little canned taps that you attach to the top of a 1 pound can you get from the auto parts store, is that correct ?.
    Unfortunately nowadays they make many different size cans that is causing a lot of confusion. Did your Ken actually say 16 ounces on the can or is it one of those small cans that they call a 1 pound can because it used to be 30 years ago because it’s our 134A it only contains 12 ounces of actual refrigerant in the 16 ounce can double check that for me please. In the old days a 1 pound can was the Phill volume bit because they had to allow for room of expansion they would put a little less refrigerant about 2 ounces less and for the new refrigerant R134 sometimes it’s up to 4 ounces less than 16 ounces which makes it 12 ounces. Possibility double check your numbers food for thought.
    6: getting back to pressures trying to diagnose a variable speed electric compressor on top of that different days ambient outdoor temperatures and humidity also plays a factor your actual pressures can be all over the ball park field . I would ask you what was your superheat and your sub cooling readings. But I know you cannot give me that answer and text stream does not provide that information either. More food for thought if I were you I would read about superheat and sub cooling in commercial HVAC training guides automotive training education level is too low to learn about such subjects .
    7: another unfortunate fact about buying aftermarket non-OEM condenser’s they are not all created equal. Let’s go back to science 101 in junior high school about the laws of physics. Mass and surface area. When you’re comparing two condensers a original OEM Toyota condenser to an aftermarket budget replacement condenser . A: Count the number of cooling passages tubes from bottom to top. Example the OEM condenser let’s say has 56 cooling tube passages. The budget aftermarket condenser example you make count there is 50 cooling tube passages. Aluminum is waight and wait is money. B: take a nice good steel ruler put it up to the fins on the condenser of both the OE condenser and the aftermarket condenser . Start with the first fun for 1 inch on the original equipment OE Toyota condenser you may count 18 or 20 fins per inch. Now count the fins per inch on the aftermarket budget condenser, you may count example somewhere between 14 and 16 fins per inch I have seen them as low as 12 per inch that was really bad quality . This will affect your high side pressure on a hot day or humid day greatly raising the pressure and reducing the BTU heat rejection capacity of the condenser lowering the efficiency of your AC system.
    8: there’s not enough information to make a diagnosis and with their condition is extremely difficult to do through a post it’s one of those things where I would be placing my fingertips before and after each component in the system to diagnose with experience not by gauge numbers . I feel there’s some information missing that you have not noticed. It could be something very simple. And if you wanted good air conditioning refrigerant manifold gauges or see some examples of other equipment visit my photo albums with explanations of procedures components and tools for air-conditioning in PriusChat .
    9: if your vehicle came to me for diagnostics with the information you provided knowing somebody worked on it who is not 100% proficient in air-conditioning and does not work with it every day I would start with the following . A: I would hook up my refrigerant gas analyzer to make sure you did not accidentally get air into the systems between the time you removed your hose off the vacuum pump to the time you hooked it up to the canned tap .B: I would perform a recovery of the refrigerant in the system my equipment and my skills are accurate to within 5 g and I calibrate them manually daily unlike shops who might do it every several months if ever they just trust their equipment blindly. I would now remove the refrigerant lines off your condenser to check to see if it’s bone dry or has a nice oily residue at the outlet of your condenser since you did mention you only put back in 1 ounce of refrigerant oil 30 mL after replacing a evaporator and a condenser at the same time you may not have enough oil and have caused damage to your compressor now .
    C: I would remove the dryer sock out of that new condenser to see if it is discolored with a gray soot looks kind of smoky it should be pure white like a brand new piece of paper. D: I would flush backwards from the bottom of the outlet with the dryer sock removed through the condenser out of the upper inlet of the condenser with some flashing material for an AC system into white clean rags or tissue paper to look for any tiny small metal particles the size of the grains of sand very small flakes smaller that would girls to use on glitter on their face. That would have come from the compressor.
    E: if the dryer sock was clean and the condenser was clean with no small glitter metal flakes inside of it after flushing it out backwards then I would evacuate your system down to below 500 µm not 29 inches. I would charge from a 30 pound container of refrigerant not swapping hoses between a small can with the possibility of introducing Air. Now the car would be ready to diagnose properly knowing that it does not have contaminated refrigerant and it does precisely have the correct amount of refrigerant charged in to the system that the sticker under the hood indicated.
     
  6. Jose Conde

    Jose Conde Junior Member

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    2018 Prius 1 AC Busted blowing HOT Air only! $1998 Quoted repair cost on a car that is practically BRAND NEW! Diagnoses by Toyota of North Miami is replacement of AC Evapotor and Expansion Valve. This is highway robbery
     
  7. lech auto air conditionin

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    I have a question what is their labor rate per hour the price sounds a little high. The labor should probably be roughly 7.5 hours X labor rate=? The dealer price on parts is high so probably around $300 for the evaporator plus $150 for the expansion valve just a guess ballpark figure would =?
    You would probably want to find a local repair shop specifically one that does a lot of Prius so they don’t make any mistakes. A Toyota specialty shop or a hybrid specialty shop that’s been in business for about 8 to 10 years of experience usually don’t recommend going to new shops experimenting on customers cars just learning how to work on hybrids.

    Example here in San Francisco labor rate mechanical at $150 an hour is considered cheap. 7.5hrX $150=$1125.+ evaporator $235 expansion valve $65 = $1425.

    The Toyota dealer will always be more expensive than the private garage shop.

    What is sad is a 2018 that already has a leaky evaporator is very uncommon. Usually I don’t see evaporator leaking for another 8 to 12 years
     
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  8. Jose Conde

    Jose Conde Junior Member

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    Well the problem is fixed. But there is something strange that happened and when I can figure out how to post here I will.... The dealer pronounced the car fixed one day and then as I was getting ready to go retrieve it the next morning they said it was not ready, needed a few more hours which turned into another weekend... The initial diagnosis was wrong. The Servo Sub Assembly, Damper was bad and it was causing all the issues. This apparently is a much easier, cheaper, faster job and a correct diagnostic would have avoided the hefty charge. I wasn't charged extra for the damper, but I feel like I should be charged for that and not the faulty diagnostic. currently trying to figure out if I should fight this....thanks for your feedback.
     
  9. lech auto air conditionin

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    Did you ask to see the old part hopefully they truthfully show you your old part.

    Usually when a Prius evaporator leaks it’s very visual by the time he gets big enough to catch with a leak detector.

    It will have usually oily spot that has gather dust and turn dark anywhere from the size of a quarter to half the size of the evaporator depending on how long it’s been going on for.

    Here’s a link to my YouTube channel I show a very oily dirty evaporator just removed from a Prius.


    I have a few videos on Prius is on my channel

     
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