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Roadster HVAC Overheating Problems

Discussion in 'Roadster: Technical' started by DanielFriederich, Dec 15, 2015.

  1. Rolf68

    Rolf68 Member

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    Thanks for the info :)
     
  2. dhrivnak

    dhrivnak Active Member

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    I think this is mostly true but it seem to me the AC unit can cool the battery and cabin but battery takes priority. So you get reduced cooling rather than no cooling in the cabin. To many it may feel the same.
     
  3. DanielFriederich

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    there are two solenoid valves which connect/disconnect the pipes from HVAC th the heat exchanger located at the battery pack. These two valves are opened up when the system requests cooling of the battery.
     
  4. MLAUTO

    MLAUTO Member

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    There is one solenoid valve for the cabin A/C, the other is for the battery chiller. They are independent of each other. The cabin one is controlled by the HVAC controls and does not shut off when battery cooling is requested. It gives reduced cabin cooling due to the undersized system. When the battery coolant temp starts to drop, the cabin cooling slowly returns. This is due to the liquid to liquid heat exchanger for the battery being a lot more efficient at transferring heat than the liquid to air HVAC evaporator. The system may be designed to shut off the cabin solenoid if the battery gets extremely hot, but I have never been able to verify that.
     
  5. gregd

    gregd Active Member

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    Ha! Thanks for clarifying what I'm experiencing. Learned something new today.
     
  6. dpeilow

    dpeilow Moderator

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    Last night I charged the car on 10A at a friend's house after a sedate 120 mile drive. I got the over pressure warning almost immediately. I noticed that the battery temp rose to 40 deg C during this charge.

    On the way home I stopped half way and plugged into a 60A charging station. I didn't see any warnings during the hour it was charging but the pressure rose into the 20+ bar zone when cooling came on. When the pump isn't running it is about 7 to 8 bar.

    When I got home I triggered a cool down charge via OVMS. Watching the diagnostic screens I saw pressure go to 24 bar and the pump rpm go below 2000.

    At start of 60A charge:

    20160717_133024.jpg


    At home on cool down:

    20160717_155918.jpg


    The ramp up to 100% from the pump takes up to 10 seconds. No idea if that is normal.
     
  7. dpeilow

    dpeilow Moderator

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    I just received the following from the local SC.

    Well if the car isn't in debug mode I'm pretty sure the debug messages would clear.

    As for AC service and proper battery cooling operation, is this not a fundamental item to check during the annual service?
     
  8. MLAUTO

    MLAUTO Member

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    Based on your high pressure readings, you either have restricted airflow thru the condenser or the system is overcharged.
     
  9. dpeilow

    dpeilow Moderator

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    Yep, that's what I thought too.

    I'm a bit concerned that the best they can come up with is turn off debug messages. That's like taking the bulb out of the warning light.

    Can anyone say for sure if these checks are on the annual service schedule?
     
  10. Nvbob

    Nvbob Roadster 1256

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    David,

    I checked some previous annual service invoices and checking the HVAC was not on it.
     
  11. dpeilow

    dpeilow Moderator

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    Thanks. Seems a bit strange for a component that is critical to proper operation of the car not to be checked.

    Given that the resting pressure is around 8 bar, does that sound like over pressurisation?
     
  12. BartJ

    BartJ early member

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    It depents on the outside temperature.
    At 25c , it should be arround 4.5 to 5 bar, not more.
     
  13. dpeilow

    dpeilow Moderator

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    Thanks - actually going back to the start of the thread to the part that was merged I can see that the answers are there.

    My resting pressure of around 8 bar is obviously way too high.

    So I guess this is the problem described in the service bulletin SVC-10-18-007. I'm thinking I should just quote that back at them.
     
  14. dpeilow

    dpeilow Moderator

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    Furthermore, after a discussion earlier today, I learned that regassing of the system should have been done at least on a biannual basis as part of the service schedule. Can others confirm that?

    My understanding now is that when the car throws the HVAC compressor over temp / over pressure warning, the compressor shuts down. Therefore the battery is only being cooled by the liquid cooling circuit. If true, this might explain the 40 deg C battery temps I've been seeing even during low charge currents.
     
  15. hcsharp

    hcsharp Active Member

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    Checking the A/C system is included in the annual service. I can't find the list of things they are supposed to do right now but it's a long list and the A/C is definitely included. You are correct that your battery won't be cooled properly if it's over-charged. Turning off debug mode won't fix that.

    If you check the pressure at 25C with the system turned off you have to let it rest for a while. I'm not sure how long but I would guess an hour or two. Right after it shuts off it will still be well above 5 bar.
     
    • Informative x 1
  16. dpeilow

    dpeilow Moderator

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    I checked my two annual service service invoices and in January 2016 they performed a 48000 mile / 4 year service, which has:

    Tesla cooling.png


    Now, does this mean just the battery water / anti-freeze coolant or the whole system including the refrigerant?


    In January 2015 they did a 12000 mile / 1 year service and that doesn't mention anything about cooling.
     
  17. dpeilow

    dpeilow Moderator

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    Found this paper service report in my file.

    20160725_220044.jpg 20160725_220112-1.jpg
     
  18. dhrivnak

    dhrivnak Active Member

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    The coolant I think just means replacing the propylene glycol green fluid that goes through the battery. After about 6 years it will begin to foam causing coolant loss. Now when they perform the annual servicing they have drained and refilled my freon. A separate and different system.
     
  19. dpeilow

    dpeilow Moderator

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    Yep. But the maintenance checklist above specifically says to evacuate and refill refrigerant charge every year on a 1.5 and every second year on a 2.x.

    As I was billed for a 4th year service I presume they (should have) preformed this.

    Strange then that the earlier email following my enquiry claims there is no record of having done it.


    And interestingly my glycol coolant does foam up when the pump starts, despite that apparently having being replaced at the same service (on the invoice).
     
  20. dpeilow

    dpeilow Moderator

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    I had this again this week.

    Funnily enough I was listening to this at the time.

     

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