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Roadster HVAC Overheating Problems

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

  1. MLAUTO

    MLAUTO Member

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    Use water, you can bend the condenser fins with air from a compressor if you're not careful. Spray it down with some mild soap first (dawn works good) to help get it clean. Taking the fans off is the best way-only a couple of bolts and two connectors.
     
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  2. hcsharp

    hcsharp Active Member

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    Sprayed it down with a hose nozzle but there wasn't much debris in there. The cabin air intakes were much dirtier. Refrained from using a pressure washer. Charged 100 miles but it wasn't warm enough for the AC to come on for a proper test. If I'd known I would have tried to do a range charge to force the AC to come on. I'll post an update after a better test.
     
  3. hcsharp

    hcsharp Active Member

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    Charged about 90 miles today and switched it into range mode to make the AC come on to cool the pack. No more compressor over-temp or over-pressure messages this time. It wasn't very hot today and the AC only came on once so the jury's still out but It looks like a simple back-flush of the condenser made a difference. Thanks again to MLAUTO for this tip.

    If anyone does this themselves, I recommend parking your car on a slope with the front facing down so the dirt and debris can come out easier.
     
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  4. hcsharp

    hcsharp Active Member

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    We've been having some hot weather lately and this problem came back with both HVAC Over-temp and Over-pressure warnings when charging a warm battery. Still no problem just running the cabin A/C. So I completely removed the fans and shroud they are mounted on (not easy with two lock-nuts in a channel with no access to hold them). I back-flushed with soap and good water pressure from a hose nozzle. Put it all back together and... Now the HVAC compressor won't come on at all except for cabin A/C. Previously it would come on and cool the battery but throw warnings when the compressor ran.

    The pressure ranges from about 6 to 11 bar when running the cabin A/C. When the system is off it's about 5 bar. The HVAC diag screen says requesting 100% cooling, 0 received (when charging). I've checked all the fuses.

    Wondering if anybody has any ideas? Thanks.
     
  5. hcsharp

    hcsharp Active Member

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    I've got some more information. We had some cool weather and one morning the pack was 18C with ambient temp about 14C. I started a range charge and right away the A/C came on to cool the battery. The compressor rpms never got very high. No error messages. At rest the pressure was about 3 bar and never went over 11 bar when running.

    My new theory is the pressure is too high when it's warm and I need to drain some refrigerant. It cools the cabin and appears to cool the battery when ambient temps are low. Basically it works fine if the pressure at rest is low enough to start, and works fine at lower RPMs.

    I remembered that my car was at Tesla for something else last fall. I'm wondering now if they added some refrigerant while it was there and over-filled it. I don't remember seeing anything about HVAC on the service description but then again I may have missed it. There's no other time when it could have been filled.
     
  6. BartJ

    BartJ early member

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    Henry,

    that could very well be. But normally you should be getting HVAC compressor overpressure warnings in that case on OVMS.
     
  7. hcsharp

    hcsharp Active Member

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    I get those warnings on the VDS but only when the RPMs go higher than what's necessary for cabin A/C. My recent test the RPMs didn't go higher than that even while cooling the battery. I don't have adequate cell service at my house for OVMS. Do you (or anybody) know what the resting pressure is supposed to be in the system at 25C? I'm trying to figure out how much to bleed off. I've never done that before. I've only charged A/C systems.
     
  8. BartJ

    BartJ early member

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    I have left of some pressure myself a few weeks ago for the same issue.
    There are two valves. Let some frigerant escape through both valves, one by one, by just pushing in the valve release with a long tool for a second. Carefull for frostbite ( wear thick glove/)
    Go gently and leave of only of a bit at the time - until the overpressure errors dissappears.
     
  9. BartJ

    BartJ early member

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    Just checked my resting pressure : 4.6 bar with refrigerant being at 24C
     
  10. hcsharp

    hcsharp Active Member

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    Thank you! That's very helpful. I'll try that today. It's supposed to be hot so good day to test.

    My resting pressure at 25C is 5.7 bar.
     
  11. Rolf68

    Rolf68 Member

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    Hello BartJ

    Could you please link the youtube video you're talking about, and/or picture of the valves in the Roadster? I searched a bit under the hood but wasn't able to locate those.

    And thanks for the precious information you gave here :)

    Best regards
     
  12. DanielFriederich

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    Picture of the valves (refill system connectec to them)
    IMG_6328.jpg
     
  13. DanielFriederich

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    Did you check the two solenoid valves which open up the circuit from the front HVAC to the battery heat exchanger?
    if not PN me (have the manual for it) ;)
     
  14. Rolf68

    Rolf68 Member

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    Thanks for the picture :)

    I suppose you had to remove something in order to access those valve. I don't remember it was so "clear" under my hood. And did you take special care because of the 400V before doing anything under there?

    Best regards :)
     
  15. DanielFriederich

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    yes correct
    removed the upper plastic cover for this maintenance.

    400V: no special actions taken since the DC/DC converter is completely untouched...

    but (at least in Germany) you have to get a mechanic being certified for electrical vehicles or at least willing to work on the car (without that paper ;) )
     
  16. dpeilow

    dpeilow Moderator

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    I recently saw several messages appear during charging that said the HVAC compressor was over temp and over pressure.

    This happened several times in succession for a couple of weeks but not for the past 2 or 3 charges. Now I notice the coolant in the reservoir by the battery has dropped noticably. Anything to worry about? Is it likely the service centre overfilled it last time?

    20160528_170342.jpg 20160528_170334.jpg
     
  17. DrComputer

    DrComputer Active Member

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    Be very cautious of this! Two years ago the service center over-filled the freon in my HVAC system and it caused the compressor to turn off during charging but the charging continued. I happened to be in the garage when this happened and I smelled something burning from the car. Unfortunately, the firmware didn't stop the charging even though the AC compressor stopped. I immediately manually stopped the charging and called Tesla. They picked up the car and diagnosed the problem as an over-filled freon issue. They refilled the system to the proper pressure and everything worked again.... until later that year when I realized that the heater no longer worked. The over-pressurized system somehow caused a failure in the heater and they had to replace the entire HVAC box (at their expense). Everything has worked fine since but be careful of those exact errors.
     
  18. BartJ

    BartJ early member

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    deg
    definately overfilled HVAC

    see other threads about this as well.
     
  19. Rolf68

    Rolf68 Member

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    Great, thanks for your answers.

    Best regards :)
     
  20. hcsharp

    hcsharp Active Member

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    No I haven't checked that, but it's a good idea. I've had a lot of clues that led me astray. First I didn't think anybody has touched my car in many months so I dismissed the over-charged theory. Then I remembered my car was in service last fall for something unrelated and they must have filled it. It was cool and didn't throw errors until it warmed up this spring, many months later.

    The next clue was the cabin A/C worked just fine, so I didn't think it had anything to do with A/C components, but thanks to MLAUTO I learned the battery cooling can run the compressor twice as fast and I cleaned the condenser.

    I've drained some fluid/gas to where it's about the same as BartJ. It appears to be working but haven't had a real good test yet. If I get more errors I will look at the solenoid valves. Thanks for everyone's help.
     
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