1. popptj2001

    popptj2001 Member

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    I just replaced my AC evap core and am having an issue. AC only cools when temp is set to "Lo". When raising the thermostat even one degree, AC vent shifts to floor and blows hot air. Steering wheel control does the same thing.



    After disassembling and reassembling the entire dash, I'm sure it is possible to have hooked something up incorrectly. Any ideas guys?
     
    #1 popptj2001, Jul 24, 2017
    Last edited: Jul 24, 2017
  2. Patrick Wong

    Patrick Wong DIY Enthusiast

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    My guess is that the A/C Room Temp Sensor was not reconnected, or the connection is bad. That sensor provides info to the A/C Control Assembly regarding how cold it is in the passenger cabin, so that the auto air conditioning function can work.

    Typically the sensor is a thermistor which develops a high resistance when cold and a low resistance when hot. So if the sensor is unplugged, the resistance perceived by the A/C Control is infinite, hence the A/C Control will think it is freezing in the passenger cabin, and will turn on the heat when the temp is at any setting other than MAX COLD (which forces the A/C compressor to run constantly.)

    Do you have photos showing your instrument panel disassembly? How hard was it to get to the evaporator? Any lessons learned that you can share with the group?
     
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  3. popptj2001

    popptj2001 Member

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    I have a ton of pics and video, and it was pretty dang tough to get to the evaporator. I will upload more when I get home. My evaporator was indeed leaking and in pretty bad shape. I have a ton of miles on my car so it was kind of expected. Patrick, any idea where this sensor might be?
     

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  4. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I haven't had to do this job yet. I understand the sensor is buried in the instrument panel near the center, based upon the repair manual diagram.
    AC diagram.PNG
     
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  5. popptj2001

    popptj2001 Member

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    Thanks. That's a good diagram and gives me some hope that it will be a shallow dig. You really have to take your time and make damn sure you get it all hooked back up. Look at this pic.
     

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  6. popptj2001

    popptj2001 Member

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    Well Patrick, I removed the lower panel just below the steering wheel and there was a lonely connector dangling all by itself. I just laughed...I'll be damned, there it is.

    Had to pop out the drivers side vent by the door, the panel with the start button, the vent next to the shifter, then and also remove the shifter, then pop out the ac room temperature sensor and saw the connection was not terminated. Fished the wire up to the connector, connected, and now, everything works!

    If anyone tries to replace the evaporator core and expansion valve, there is a good video to get you started on YouTube. It shows how to disassemble the dashboard. Will posts pics as soon as I can. Just go slow and double check as you go back together. The blower and the box containing the evaporator core and the heater core SEPARATE. I cracked one of the plastic braces trying to move them both out together. If I had used the Toyota manual I would have known that. Nothing that a drill and strategically placed tie wraps can't fix!

    Anyway, a successful evaporator core and expansion valve replacement.

    Tks Patrick!
     
    #6 popptj2001, Jul 24, 2017
    Last edited: Jul 25, 2017
  7. popptj2001

    popptj2001 Member

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    Here is the evaporator core I pulled out. As you would imagine, my AC now works sooooo much better!!!! I thought I did a pretty good job cleaning my cabin air filter but as I said I have a ton of miles on my car. Just thought I'd post the pic of the core. And by the way, the heater core looked brand new.
     

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  8. 05PreeUs

    05PreeUs Senior Member

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    That would be a horrible job to do!
     
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  9. popptj2001

    popptj2001 Member

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    Any idea what this cost at a Toyota dealership?? Evap core, exp valve, also replaced condenser as it was totally clogged internally. Vac and fill.
     
  10. Mendel Leisk

    Mendel Leisk Lapsed Cargo Cultist

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    Lots of AC use, means lots of condensation collecting on the fins: a dust trap. Would you be able to get at it, without pulling half the dash apart?

    Edit: looking at your pics above, it looks nuts. Hope I never need to do something like this.
     
    #10 Mendel Leisk, Jul 26, 2017
    Last edited: Jul 26, 2017
  11. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Odometer reading?

    How did you know the condenser was clogged?

    Also, if you wish to post more photos I am sure the group would appreciate seeing them. I certainly would as I may face a similar task with the 2007 in the fall (too hot now to do that kind of work here.) The system has a tiny leak, it continues to work when I add just a few ounces of R-134a each year. But that won't last forever. The leak is not obvious even after dealer-added dye, so it may be at the evaporator or some other part hidden from casual inspection.
     
    #11 Patrick Wong, Jul 26, 2017
    Last edited: Jul 26, 2017
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  12. popptj2001

    popptj2001 Member

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    It would have been nice to have an access panel to get it out, but noooo....you must remove the entire dash to get to the evaporator core.

    Under the hood, it's easier to start by removing the hood.....then go ahead and remove the wiper assembly, plastic pieces that cover the wipers, the wiper cowling, disconnect the AC lines (with a special disconnect tool) after refrigerant is evacuated, and the heater core hoses. Flush and blow out ALL the lines well...I used brake cleaner and compressed air. Also make sure your condenser is not clogged internally or externally...flush it also with brake cleaner and blow it out. IF it's heavily restricted, replace it (I had to replace mine). After I recharged my system, the low side went negative when the compressor engaged. WTH....that's when I discovered the condenser was clogged. Today I was logging 44 degrees out of the vent :)

    And yes I added the proper hybrid oil to the system....to the evap core, compressor, and condenser.
     
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  13. popptj2001

    popptj2001 Member

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    Odometer reading---475,000....Yes I will make 500,000 if it kills me.

    Patrick...I never found my leak either...mine was bad. I was adding a can every few weeks. But, when I removed the evaporator core, I noticed a stream of dye that had trickled down the drain tube. I didn't check there. Maybe I didn't want to look there....lol.
     
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  14. Patrick Wong

    Patrick Wong DIY Enthusiast

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    I didn't know you could use brake parts cleaner on the AC plumbing.

    44 degrees F sounds pretty good, what is the ambient air temp?

    I posted some photos a few years ago of the 2004, showing around 37 degrees F coming out of one of the center vents, with ambient air temp around 95 degrees F. That was because some owners thought it was OK to have MAX COLD air temp only in the 60's...should be very close to freezing.
     
  15. ChapmanF

    ChapmanF Senior Member

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    I hope that's ok ... I think of brake cleaner as pretty chemically aggressive stuff, and I'm not sure exactly what kind of coating insulates the high-voltage windings in the compressor. I'd be happiest being sure there was no trace of that stuff left in there.

    Your picture of the evaporator was a bit shocking ... I wonder if there's much chance of snaking an inspection camera back there, short of disassembling the dash....

    -Chap
     
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  16. popptj2001

    popptj2001 Member

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    I researched using brake cleaner...and seems to be ok. I say ok.....it didn't pertain to electric compresors. After I blew through everything, I left it open for a day just to make sure. It's hot here in South Texas, so I'm pretty sure it all evaporated....hopefully all is ok. So good so far.
     
  17. popptj2001

    popptj2001 Member

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    Outside temperature was around 98 I believe when I had the 44 degree reading.
     

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  18. 05PreeUs

    05PreeUs Senior Member

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    You *can* use olive oil too, but neither is recommended for the job.... ;)

    They make AC flushing solvent, even in compressed delivery cans using dry N2 to ensure you do not introduce moisture into your system... which is the world's fastest way to KILL your AC components.

    Back in the day..., LOL, the standard was ambient less 30*F or so, this was considered decent AC. Ambient less 40* was awesome. Today, with a dewpoint lower than 65*F, you should easily attain ambient less 50*F from an AC system in good repair when measured from one of the center panel registers, the vehicle in the shade and the condenser fans running.
     
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  19. popptj2001

    popptj2001 Member

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    Well they were all out of Olive oil so brake cleaner had to do.

    I didnt flush the compressor. I simply drained the old oil out and added new.
     
  20. popptj2001

    popptj2001 Member

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    Patrick.....Here are the pics and videos I made of the removal. This is not instructional media, simply for me to document how things went back. There is a large molded plastic frame that must be removed. You can see it Some pics and video....I didn't really address it. Just maneuver the wires around it out then back into place going back.

    Dropbox - Prius Evaperator Core Replacement

    Also the first part of this YouTube video shows the first steps in disassembling the dash.

     
    #20 popptj2001, Jul 27, 2017
    Last edited: Jul 27, 2017
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