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Air conditioning gave up in Palm Springs, works in LA

Discussion in 'Gen 2 Prius Technical Discussion' started by Gil Dawson, Aug 9, 2009.

  1. Gil Dawson

    Gil Dawson Junior Member

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    Our brand-new-to-us 2006 Prius's air conditioning works fine in LA, but not in Palm Springs.

    The outside air temperature indicated 118°F Saturday (mid-August) as we slowed into Palm Canyon Drive. We had been plenty cool enough in the cabin all the way from Los Angeles.

    After maybe ten to fifteen minutes in medium traffic, though, the air coming out of the vents began to get warm.

    Less than a minute later, the vent air got cool again. Then it got warm again, then cool, back and forth. The oscillations had a period of less than a minute, and made me think of a thermal cutout switch opening, cooling off, then closing again.

    The cooling part of the duty cycle soon got short enough that the cabin became uncomfortable, so we opened the windows and shut off the air conditioner for the rest of Saturday afternoon. Love that dry desert heat!

    This morning we drove back to LA. The OAT never got above 90°F on the return trip, and the air conditioning worked fine the whole way.

    While a temperature cutout on the compressor motor might seem a plausible explanation, I'm not sure whether the compressor motor actually has a thermal cutout switch.

    Also, I've heard that the Prius's air conditioning computer makes compressor speed decisions based on a lot of information from sources that the scorching temperatures might have rendered unreliable.

    Would you have any theory as to what might have caused this phenomenon, or any tests I might perform when we go back to Palm Springs?

    We just got the car last month, and we're still learning its quirks, so I'm looking forward to any suggestion anyone may have.

    --Gil
     
  2. dogfriend

    dogfriend Human - Animal Hybrid

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    I'm wondering if the battery SOC (state of charge) was getting low when you were in the stop and go traffic and the AC was cycling because of the SOC. I've noticed that in temps above 100°F, the battery SOC can get depleted pretty quickly, to the point where the car begins to rev the ICE (internal combustion engine) more because the battery is at the low end of the range (purple bars on the display). Remember that the Prius AC compressor is completely electrically powered; it has its own inverter section just to power the compressor.
     
  3. jayman

    jayman Senior Member

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    An A/C system that is somewhat undercharged, will work ok enough in moderate temps, but in severe hot temps, conk out
     
  4. Gil Dawson

    Gil Dawson Junior Member

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    Thanks, guys, for some valuable suggestions.

    Dogfriend's hypothesis about the low SOC is very interesting, and easy to check next time.

    Have you heard whether other Prius owners have experienced the same thing?

    An undercharged A/C had not occurred to me, Jayman, but that sure sounds just like my symptoms.

    So I guess my plan is to drive out to Toyota of the Desert in Cathedral City and see whether I can get it to happen again while I'm watching the SOC gauge.

    Anyone have a recommendation for a service rep at T of the D?

    --Gil
     
  5. jayman

    jayman Senior Member

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    There are detailed performance checks in the service manual. Another possibility is moisture in the system, which is possible in an older A/C system. The cure is to replace the dryer, and evacuate/recharge the A/C system.

    It's important that only ND-11 oil be used in the Prius A/C system. This is a unique automotive A/C system, and a special oil is required to maintain proper electrical resistance for the variable speed electric compressor

    We have had some Prius cars lose the A/C due to road debris damaging the aluminum A/C condenser in front of the rad. Inspect yours for evidence of road damage. IF there is damage, the repair will be expensive
     
  6. Sandy

    Sandy Hippi Chick

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    something like this happened to me the other day it was so hot here turned it on and blew hot air so drove 10 miles and stopped at a store, when i restarted it the AC was cold, I really found that strange but it was at least 95 degrees.
     
  7. Patrick Wong

    Patrick Wong DIY Enthusiast

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    Although I don't have a specific recommendation regarding a service writer, I had a good experience with that dealership a few years ago regarding my 2001 where the engine refused to run, which resulted in a correct diagnosis and a new engine ECU covered under warranty.

    I also think that the root cause is low refrigerant in the AC system. Good luck.
     
  8. vertex

    vertex Active Member

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    I recharged my AC with 1 can of Freon (12 oz) last month. It seems to work fine, but now that we have 90 degree days here, when the car sits in the sun, it just doesn't get going. I know I am 4 oz short of a full charge. I didn't want to open a new 12 oz can and end up leaking the rest out. I have to see if I can find smaller cans. As long as you are only adding some Freon, since it works, you don't need to add oil. If you have a big leak, then you need more oil, since you may have lost some. However, if anyone needs oil, I have a lifetime supply + for myself, so I can sell it less expensively then the dealer or Car Quest. IF you get a recharge kit with a gauge, you can easily check the pressure, and top it off yourself. They cost under $20. Don't use a hose that was used on another car. If it had an oil recharge can on it, you will contaminate the oil with the old AC oil. Never use a Freon can with oil in it on the Prius, it is not ND-11 or equivalent.
     
  9. richard schumacher

    richard schumacher shortbus driver

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    The system is completely closed with no rotating seals anywhere. If it needs a recharge it has a leak somewhere.
     
  10. upaya

    upaya New Member

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    I have been experiencing same A/C pblm...blowing warmish air at slowere traffic speeds 30-40mph, yet cool at idle or higher speeds. My local dealer has replaced the compressor to no avail...they can't seem to figure it out. My online research suggests that there may be a pblm with the A/C Amplifier (also called A/C ECU). As I understand it, this device after gathering info then sends input to the HV ECU which revs up or down the compressor. I plan to present this hypothesis to the dealer tomorrow (been there 5x now). ...will report back.
    Still under warranty.
     
  11. Gil Dawson

    Gil Dawson Junior Member

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    Wow! You guys are really helpful!

    It's great to know our car is not the only one with this problem. It's odd, isn't it, that the A/C works fine most of the time (when it isn't scorchingly hot)?

    I checked the condenser and it looks fine, as far as I can tell.

    I'm a little reticent to add freon or oil at this stage, because the air conditioning works fine most of the time.

    Jayman, you mentioned detailed performance checks in the service manual. I bought a Bently manual for the repair and maintenance of the 2004-2008 Prii (we have a 2006), but it doesn't have any procedures for the air conditioner. Which service manual are you using?

    I got another hypothesis from an old industrial air conditioning experience -- freezing up. When the evaporator coil (inside the cabin air ducting) gets cold, water condenses and runs out a tube. However, if the evaporator coil gets below freezing, frost will form on the plates instead of water. Enough frost, and the air from the blower cannot get through the evaporator any more.

    For this hypothesis to work, the air would have to find an easy way around the frozen-up evaporator coil, because the volume of air coming out the dash vents doesn't seem to diminish much, it just gets warm. Anybody know if there is a path that air could flow around, rather than through, the evaporator coil inside the Prius's air ducting?

    This hypothesis would play out more likely in humid weather, like Florida, rather than dry, like Palm Springs. Still, it's a possibility that might be easy to check for. Any ideas?

    I'll be driving back out to the desert in a week or so, armed with your suggestions, and we'll see what I can figure out.

    Thanks very much for your help.

    --Gil
     
  12. jayman

    jayman Senior Member

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    I have a subscription to All Data DIY. They have the same exact data as the official TIS data.
     
  13. Sandy

    Sandy Hippi Chick

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    Mine worked perfect today and it was almost the same temp.. Love my Pri it repairs itself :)
     
  14. richard schumacher

    richard schumacher shortbus driver

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    My guess is that low-speed driving in 118'F/48'C heat is just beyond the design space of the AC system. I would also bet that Toyota designed the thing never to freeze up (it only takes one sensor feeding the ECU).
     
  15. Doug Davis

    Doug Davis New Member

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    I am currently experiencing this problem. In more normal weather, the AC works perfectly normally. When it gets over 85F outside, the AC stops working completely. The compressor does not run and the condenser fan does not run. The AC just blows hot air. This is a binary problem - it either works normally or it stops completely - no in-betweens.
    The compressor is a direct electric motor drive so no belts are involved. When AC fails, hot air is circulating thru the evap, so there is no ice-up.
    I suspect a sensor in the system is turning the compressor off, but I don't know what sensor or why.
     
  16. Britprius

    Britprius Senior Member

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    To check the level of charge in the AC system.
    Turn AC on full cold and max fan speed with doors open. If bubbles can be seen in sight glass by high pressure port the system is low on pressure if no bubbles and DTC 86 is output system is very low or empty. Immediately the system is turned off foaming should appear and the become clear for correct level. If foaming does not appear but system works it is over filled and some gas should be removed.

    Check both fans in front of condenser run and are blowing in through the condenser, it is not unknown for the fan blades to be swapped over so that they blow the wrong way.
     
  17. KK6PD

    KK6PD _ . _ . / _ _ . _

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    Don't even think of going to Phoenix in July! The only time I went, and it was in a vehicle I owned prior to the Prius, the AC blew an overpressure safety valve, POOF, NO AC, CRAP! It cost a couple of hundred to replace parts and recharge system!
    Stay away from Phoenix!
     
  18. nh7o

    nh7o Off grid since 1980

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    One way for that type of behavior to occur is with moisture in the system. Water vapor can freeze at the expansion valve, and it eventually blocks completely. The system will then heat up and the block will thaw. The A/C will start working again, only to repeat the cycle again. For moisture to get in, there was a problem from the factory, or there was contamination from a refill at some point, or a leak is present that caused the system to have negative pressure and suck in some outside air.
     
  19. lech auto air conditionin

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    One thing you can test is , at the time it goes warm it the return line to the compressor cold ?. If cold the but not cold out dash then the cold air is being blocked or bypassed. This only works on a full A/C system and not a over full A/C system not a under full A/C. Just 3 oz or 90g makes a big differences on a hot day.
     
  20. lech auto air conditionin

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    I have come across a few funny problems with pruis and A/C problems. Most of them cause by who worked on them before. especially with old a/c recharging machines that are off by a few oz, that was ok for old big cars with 2+ lb of refrigerant but not good for a pruis under 480 g. contaminated refrigerant, or old used refrigerant not properly recycled with moisture as some one mentioned before.