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2004 Prius A/C Not Working, Need Help With Diagnosis

Discussion in 'Gen 2 Prius Technical Discussion' started by veegish, Apr 12, 2023.

  1. veegish

    veegish Junior Member

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    I recently bought a 2004 base model (my boys attempted a manned flight off a snowbank with my '07 touring). I'm fairly handy as a DIY, and on the '07 I've repaired the combo meter (soldered in the new caps), HV battery replaced, swapped out the transmission myself when MG2 went out, inverter pump, etc. I know my way around a Prius fairly well, is what I'm saying. Definitely not at the level of most of you, but I prefer to do the work myself (I enjoy working on them and dislike paying others to do it if I can do it).

    Here's the situation: With the system on MAX COOL, the fan on high, and A/C on, I get warm air. Before doing three or so hours of PriusChat forum learning I was about to add some off-the-shelf r-134 but when I hooked up the gauge (on the can) to the low side port the pressure was over 75psi, perhaps indicating overcharged. I may or may not have discharged the pressure "a bit" to see if I could get anything showing in the sight glass. Nothing. With the pressure on the low side down to 5 I added a bit of that can of pure r-134, but after only a half second of charging the pressure was back up to 75. That seemed wrong to me so I disconnected and did some research and learned how different the A/C system is in these machines. Thankfully I added almost nothing to the system, but what I used did not have oil added so at least there's that.

    I know there are so many directions to take, but I can't figure out where to go from here. The 10A fuse in the cabin is good. The inverter coolant pump is working. I can't tell if the compressor is kicking on, but as I said, nothing is happening in the sight glass, it's clear all the time.

    Here's a link to a short recording of what it sounds like when I have the car on and the A/C running at max.



    Thoughts?
     
  2. Tombukt2

    Tombukt2 Senior Member

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    When you hook up your can or gauge from the can to the 134a low side fat hose port You should see between 80 and 100 lb probably no more The minute the air conditioner compressor kicks on it's going to suck down that 80 to 100 lb to about 30 and then that being sucked down is now pushing your high side up to probably around 200ish 230 .. That's how the system works there's no high and low side when the compressor is off the high and low side will read about 100 lb on your gauge on both sides because both sides are equalized when the compressor's off
     
  3. ChapmanF

    ChapmanF Senior Member

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    The thing you noticed isn't really even something different in these machines.

    Something we don't always explain well enough is that when the compressor's off, refrigerant pressure is just a thermometer. If your refrigerant showed 75 psi on a gauge, that's roughly 90 psi absolute, or about 620 kPa, and you can just look on an R134a saturation pressure/temperature chart and see the refrigerant in the car was somewhere around 23 ℃.

    R134a at around 23 ℃ will just always be around 620 kPa, or 75 psi on a gauge, as long as there is enough R134a there for any of it to be liquid. Adding more or letting any out won't change that pressure at that temperature, until you have let enough out that there isn't any left in liquid form. Then you'll see the pressure going down.

    Start adding some, and you'll see the pressure going up, until there's enough there for some to be liquid, and then it'll just settle around whatever pressure goes with the temperature even as you keep adding more.

    That's why looking at a pressure gauge to decide how much refrigerant you've got doesn't really work as well as people expect. :)
     
  4. veegish

    veegish Junior Member

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    That’s helpful! I’ll report back after another look!
     
  5. veegish

    veegish Junior Member

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    Well, I hooked the gauge back up and the pressure was around 65. Ran the AC on high and all that. I didn’t observe anything from the compressor. Like maybe it’s not turning on. No pressure change. No noticeable sound. The ICE kicked on a couple times. I gave it 15 minutes.

    Oh, and no cold air from the vents.
     
  6. mr_guy_mann

    mr_guy_mann Senior Member

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    Until the compressor turns on and starts pumping, the entire system will show static pressure. That's mostly determined by temperature, and on a hot day that'll be over 100 psi.

    When the system runs, you get high pressure (from the compressor outlet, condenser, to the expansion device) and low pressure (expansion device, evaporator, to the compressor inlet).

    So the best way to see what's going on is to hook up a pressure gauge set to the low and high service ports.

    Lacking that, use a compatible scantool to see HVAC data - or even hybrid control (inverter) data.

    https://priuschat.com/index.php?posts/3290690

    Posted via the PriusChat mobile app.
     
  7. veegish

    veegish Junior Member

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    Thank you. I’ll get some legit gauges and test it tonight or tomorrow. I appreciate the help.
     
  8. SFO

    SFO Senior Member

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  9. veegish

    veegish Junior Member

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    Ran the A/C max cool, fans high, for about 25 minutes with no change in the gauges. Stayed just like this photo.
     

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  10. veegish

    veegish Junior Member

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    Are there any relays or fuses that could be an issue? Or something else not allowing the compressor to kick on.

    I do have a junkyard compressor (scavenged today) from an ‘09 I could swap out if I need to.

    Also wondering if a bad clock spring (no horn, no right side defrost/recirc controls working) could have any impact?
     
    #10 veegish, Apr 15, 2023
    Last edited: Apr 15, 2023
  11. Tombukt2

    Tombukt2 Senior Member

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    I would certainly replace the clock spring You could get it from a used '09 where you got the compressor and it's been changed already it'll be fine If it's not broken it'll be fine If it is well then you'll need another one or you can buy a new one for 80 bucks or something like that Make sure the red lines are lined up on the clear window when you install it It's all in the book and it's all here in pictures somewhere some little send it to you pretty quickly I'm sure.. do you not hear the compressor It makes a distinct noise when it comes on obviously it's not running because even if it was bad it would not be zero on both gauges You would at least see some kind of movement on the low side even if it was only 10 lb then you'd know it's not capable of pumping or it's so low on gas what have you If it's that low on gas it'll try to run up to 9,000 RPMs to pump nothing or pump very little of something just because that's how it will work as soon as proper gas is there it'll never need to see the 8,000 RPM or high RPM like that.
     
  12. veegish

    veegish Junior Member

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    Thanks, Tombuk2!

    I did grab the clock spring while I was under the '09. Just replaced it and it was worn out even more than the '04 clock spring. Now none of the steering wheel buttons work. I've got a new one ordered and hope to see it Tuesday.

    The plot thickens, as they say. When I went to disconnect the 12v battery before removing the airbag, I found this guy (top) in the cargo space above the spare tire. It has markings on it in orange that lead me to believe it's a used unit that the PO bought at some point, probably intending to swap the compressor. I have no idea if he diagnosed it properly as bad or just thought he'd give it a try. The one from the '09 is the lower one. I am not committed to replacing it just yet, there are too many variables still. There was also a box for the cabin air filter and a new inverter coolant pump (both items have been mentioned on the interwebs as a possible reason for no A/C cooling). Seems at some point the PO or PPO started trying to fix this issue but never did. My inverter pump seems to be working fine, so at least I have a backup if needed. My last Prius (2007) had one go out while I was driving and I had to replace it in the AutoZone parking lot while I was still recovering from Covid. That was rough.
     

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  13. Tombukt2

    Tombukt2 Senior Member

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    Yeah anything that reeks havoc on the cooling system can shut the air conditioning compressor down The computer knows to turn it off because it's getting too hot and compressor generates more heat etc etc so on and so forth so generally if your AM too fuse is good You have movement in the inverter coolant system your regular water pump is working You're maintaining fairly normal temperatures which is generally pretty easy to do in the Prius even in the summer The air should be generally speaking working or at least the compressor should come on and if these conditions are met see if you're actually getting power through the thing could be the inverter having an issue getting power to the compressor there's a board or something in there I'm not sure exactly how it all works having pulled it apart to see. But to be honest with you I've seen very few of these compressors go bad me seeing them anyway I haven't replaced maybe one and I don't think it was bad I think there was another problem but I changed it anyway because what I had was a lot newer less miles all the nonsense and I do like my hair I didn't used to care for it much now I use it quite a bit and I'm not having it broken and I do like the way it works I like it better than my belt driven setups I'd even like to put this in one of my Corollas but there's no battery there for it and so forget it.
     
  14. TMR-JWAP

    TMR-JWAP Senior Member

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    if you were to get techstream, you can see what the AC system is actually doing.
     
  15. veegish

    veegish Junior Member

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    I’d need a PC laptop (don’t have one, I’m a Mac guy). Probably I could find a used one cheap. I’ve seen a lot of mentions of Techstream but when I look it up online it’s expensive. Am I looking in the wrong place?
     
  16. ChapmanF

    ChapmanF Senior Member

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    Sometimes people run it on a Mac in virtualized Windows.

    You're probably finding references to bundled pricing that includes a rather expensive dongle and a full year of activation, more like what a working mechanic shop might want. Take a look at this post.
     
  17. TMR-JWAP

    TMR-JWAP Senior Member

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    You're driving a computer (actually 15-18 of them) with 4 wheels. Life is much easier if you have a good way to communicate with them.
    If you're DIY you really need it. If not, shooting the new parts cannon at the car is going to end up being pretty expensive. May end up being less expensive to just take it to a good shop.
     
  18. mr_guy_mann

    mr_guy_mann Senior Member

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    Or you can read the review thread at the top of this forum. There are several apps and OBD2 devices that turn your smartphone into a scantool.

    Posted via the PriusChat mobile app.
     
  19. alftoy

    alftoy Senior Member

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    Techstream in a VirtualBox.

    toyota techstream Mac - Google Search

    how I got techstream on a 64 bit pc in 5 minutes - YouTube
    Toyota Techstream for ALL Windows | How to Install and get it WORKING Everytime | Landcruiser 200 - YouTube

    5 min to Download + Install Techstream V12 VMware for VXDIAG Toyota | OBDII365.com Official Blog
     
  20. lech auto air conditionin

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    Did not have time to read through the whole post only the very first one mentioning the problem, and I did watch the video with the noise.
    Pressures almost mean nothing whether the system is full or empty unless the pressures are absorbently. Extreme.
    If your car has not been running and you put your pressure gauge on it in the morning and it was 45°F last night when you hook up the low side you’ll probably see somewhere around 45 psi on the low side even if the system is 100% full even if the system is three or 4 ounces overcharged, you will still see only 45 psi on the low side even if you only have one drop of liquid refrigerant left in your system at 45° ambient air temperature you’ll be somewhere close to 45 psi pressure. This does not mean you are low. This does not mean you were full and it does not tell you if you were overcharged. . This is How Refrigerant response to temperature..

    I know the hand if it was 80°F outside and you just drove back from the shopping mall and parked your vehicle. You now have a nice toasty crispy hot engine compartment. You have the doors and windows closed and the inside of the passenger compartment has gotten hot in the last 10 minutes might be 100° inside the passenger compartment and you hook up your low side pressure gauge, you might see 110 psi on the low side gauge and that two will be normal for that temperature of all the hot engine components because the refrigerant lines are now hot and soaked from the heat under the hood and again whether you have 1 ounce of refrigerant, or the exact, correct refrigerant charge or you had any container that contain 10,000 pounds of refrigerant but at that same temperature they will all be the same pressure so do not let anybody tell you that you can tell a full system from a slightly low system so long as there’s one drop of liquid refrigerant to a given temperature it will follow the PT chart for that particular refrigerant.

    Now under that same condition if you hooked up your low side gauge and it was 80° plus outside and you’re gay tony said 30 psi you only have vapor you’re almost empty. And that too, you could tell by looking at the PT chart for the Refrigerant temperature pressure relationship..

    Now let’s get to the noise in the video I could not hear it very clearly, but it almost sounds like the compressor trying to engage and you describe the fans were coming on at the exact same time. So this sounds like a not so happy compressor sound. I have posted videos on this on my YouTube channel and in my previous chat photos and video album on Prius chat.

    If you have a cheap set of gauges. You can use some of your new refrigerant to purge the air out of your gauges.. because you don’t wanna hook up a new set of gauges that are filled with air in the lines to your system.

    Unless you have a vacuum pump to vacuum all the air out of the gauges when you connect them.

    If you could take a video of the high side and low side pressure when that sound, that sounds like a compressor tries to kick in.

    Another thing you can do take a long extension bar for your socket set or a pipe or a long cylinder from gift, wrapping paper that cardboard put it down and place it to the Body chassis of the compressor and put your ear to the other end so you can hear

    When the sound comes on with your ear, at the other end of either a steel rod or a long hollow tube, can you identify that the sound is coming directly off of the compressor case shell.

    Because what you’re describing is a classic sign in for a ride I think I hear from your recording is the compressor trying to engage it does not the computer notices that in instantly kills the power to the compressor and your fan shut off.

    And sometimes, if you do that enough, it will permanently turn off after about three or four attempts, and set a code for over amping telling you the compressor is drying too many amps because it’s locked up