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Air conditioning cycles to warm? Normal?

Discussion in 'Roadster' started by arijaycomet, Jun 9, 2018.

  1. arijaycomet

    arijaycomet Member

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    Hey folks. Currently on a 1200 mile epic journey home from Florida to Ohio. It’s pretty toasty down here as you may imagine. Have had the air con pretty much running non stop. Every 10-15 minutes the AC condenser seems to cycle off for about 45-60 seconds. Then comes right back on. With no user input.

    Driving in range mode. Roadster 613 2.0 with r80 upgrade. New car to me. 4500 miles young.

    Is this behavior normal? When condenser is on we get super cold and comfy temps. So maybe his is a function of range mode? Or just the condenser not wanting to overheat?
     
  2. gregd

    gregd Active Member

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    What high is the battery temperature running? By "cycle off" do you mean that the temperature in the cabin increases for a few minutes (versus the actual compressor stopping)?

    It could be that the car is diverting some of the cooling to pull the battery temps down. If so, that's quite normal. Annoying, perhaps, but normal. There's just not enough cooling capacity to do both at the same time, and the car is trying to protect itself.
     
  3. arijaycomet

    arijaycomet Member

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    You are correct that I have no clue about compressor. Simply what happens is as you described. Cabin gets warm. Air blows but not chilled. But then a minute later all is right again. Sounds like based on your matching description this is just normal fare. Maybe next time it happens I should check the temps screen? It may be doing this when in yellow versus blue? Thanks so much!
     
  4. gregd

    gregd Active Member

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    Yes, sounds normal then. The battery temp shouldn't get into the yellow zone if you're just driving normally. If it does, you'll probably get an alert that the battery is too hot and that the car is reducing power as a measure to help it cool down. If that happens, definitely slow down. A hot battery is not a happy battery.
     
  5. arijaycomet

    arijaycomet Member

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    At this point it has not yet gotten into the yellow that i’ve Seen, nor any warnings. I have a co-driver so we keep good tabs on the menus, temps, etc. Thanks again for all your speedy help!
     
  6. MLAUTO

    MLAUTO Member

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    It has nothing to due with the battery cooling. When the battery starts to cool you will lose the A/C for about 5 minutes and the compressor noise will be a lot louder. Either there is too much refrigerant in the system or the evaporator is getting plugged with debris. The compressor will turn off when the evaporator temp gets too low to prevent the system from icing up. Since Lotus poorly designed the air intake under the front bumper instead of at the windshield cowl (and with no filter), all the road dust eventually starts to plug up the evaporator. Low flow drops the evaporator temp (so output seems fine) and the system shuts down for about a minute until it warms up. Then the cycle starts again. The same will happen with too much refrigerant. Probably best to make due until you get home, as finding someone who can actually fix it on the road is probably impossible.
     
    • Informative x 3
  7. backmost

    backmost Member

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    How often would you recommend to inspect and clean the fans?
     
  8. MLAUTO

    MLAUTO Member

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    Its not the fans but the evaporator which is buried at the bottom underneath the hood. So it is not something you can easily do as a preventative measure. It all depends on how much road debris gets sucked up into the system-mostly it is animal hair that starts to plug it up. You can clean the condenser by flushing water thru the cooling fans, but that only corrects low performance from the A/C, which was not the OP's problem.
     
  9. gregd

    gregd Active Member

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    So, MLAUTO's explanation could also apply, but from my experience I'm still voting for battery cooling. I think what would determine which it is would be how often the cycling occurs, and for how long.

    Before I retired, my afternoon commutes home during the summer would occasionally trip the car into the battery cooling I described. All running normal, AC keeping me more-or-less cool. Then I'd hear a soft click and notice the cabin would get warmer for about two minutes, then go back to normal. MLAUTO says it's a bit longer, but I really don't remember it being 5 minutes. The cycle would not happen frequently - at least 5 minutes or so between events - but then my 1,000 foot hill climb would be over and I'd soon be home. Battery temps never hit the yellow in all this; no VDS warnings, and nothing in the logs.

    Fast forward to a week ago, when I drove to visit family some 220 miles away (i.e. beyond a single charge in this car). The return trip was hot, with the ambient temps in the 98 to 102 F range, and I noticed that the AC would be frequently doing short cycles. Because of the range challenge, I didn't have the AC on in the cabin, but I could feel its effect since when the AC starts to cool the battery, it also cools the cabin a bit. The battery is just a better sink for the cold, so it gets most of the benefit. The car is noisy enough at freeway speeds that I can't really hear the AC compressor, but I could hear the click, and enjoyed the slightly cooler cabin.

    By the time I stopped to charge, the battery and AC compressor were apparently very warm, and I got a #1463 alert (HVAC compressor overtemp) shortly after charging started. This was reported by my OVMS v3 module, not anything visible in the cabin. Foolish me, I didn't think to check the battery temp, but looking at the logs when I returned home, it was already at 43.5 C, and still climbing during the charge. The AC was doing strangely short cycles during the charge - maybe 5 seconds on, followed by several minutes off - but no further #1463s, so I figured it was ok. In hindsight, the subsequent alerts were being suppressed as dups, and the HVAC system was really struggling.

    Continuing towards home after the charge, I hit the aforementioned hill climb, and got a battery overtemp warning in the cabin. I made it home (slowed down a bunch to go easy on it), and plugged the car in. OVMS showed me that the battery was at something like 45C, and the AC system was still doing its short cycles during the charge, so I lowered the charging current to 16 amps to reduce the heat generated by charging. It finally started to cool. By morning, the battery was back to normal temps (mid-20's C) and fully charged.

    During the post-drive analysis, I find there were 1,309 of the #1463 events in the log. This, I believe (hope), is a perfect example of what MLAUTO is describing as an over-fill of the HVAC system. The car's most recent yearly maintenance was just a few months ago, so the cooling fins are likely clean. But one of the items the tech noticed was that the coolant level was "a little low", so he topped it off. I think he overdid it... The car has an appointment with the SC on Tuesday.

    So, from your description, I still think your scenario better matches my first battery cooling scenario (the normal one), rather than the second. If I recall, the normal scenario pulls the battery temp down by about one notch on the VDS display during its few-minute run. Better would be to take a look at the logs, but you'll need a USB stick and a laptop for the analysis. Search the archive for links to the VMSparser and TeslaGLoP log analysis tools (PC, or Linux via Wine), and the procedure for extracting the car's logs. It's a great way to learn more about how the car operates, and can give early warnings for things that aren't quite right.

    Do let us know what you determine the root cause to be, and best wishes for the remainder of your trip.
     
    • Informative x 1
  10. supersnoop

    supersnoop Tesla Roadster #334

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    Cycling off for a minute might be a problem, but cycling off for a few minutes would seem to be normal battery cooling. Unfortunately, you reply have to get very specific when diagnosing cars these day.

    I bought mine just when the Texas summer was starting and took it in for Tesla to check the a/c early in the season. It was (and still is) normal behavior.
     
  11. MLAUTO

    MLAUTO Member

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    Just enter the diagnostic mode and check the HVAC in the menu. It will tell you exactly what is happening. But the battery cooling cycle takes a lot longer than the minute or less timeframe stated.
     
  12. gregd

    gregd Active Member

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    Yeah, definitely should have done this. I presume that, now that everything is cooled off and (apparently) working normally, I won't see anything wrong in the diagnostics, right? What should I have looked for?
     
  13. MLAUTO

    MLAUTO Member

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    You can see the high side pressure and the cabin outlet temp, as well the compressor speed. Battery cooling runs the compressor at full speed about 6000 rpm, high A/C alone about half that. High pressure should be less than 20 Bar on a hot day. More than that and you have too much refrigerant, dirty condenser or an airflow problem. Outlet temp varies, as the evaporator temp is actually used to shut down the system if it gets too cold, but that reading is not shown. I usually see the system shut off when the outlet temp is around 8C to 10C. With the system running normal and at a steady state (car still or consent speed), all the readings should be stable. If the high side creeps up or the cabin temp keeps dropping, then you have a problem. Everything varies with outside temp and airflow, but the system adjusts the compressor speed to keep the pressures within check. If you get outside of the adjustment range, you start to have problems.
     
    • Informative x 1
  14. gregd

    gregd Active Member

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    Ha. I think that confirms it. Just finished a short run across town and back. Nice day. Ambient temps about 30C, battery not much different. Charging at 24A the AC kicks in. Compressor 100% running between 2,300 and 3,500 RPM, "Prefirgerant" running 22-ish bar, getting to a peak of 23.6 bar. Too much refrigerant confirmed? I'll show the tech the movie tomorrow... (This is a 2.0 car, btw.) Here's a typical image during the charging session:

    HVAC during charging.jpg

    Thanks for the side discussion. Back to the OP's topic... How's the trip going?
     
    • Informative x 1
  15. MLAUTO

    MLAUTO Member

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    Peek up thru the front grill and look at the condenser for debris restricting airflow. Otherwise, yes, it looks like too much juice making the compressor work too hard.
     
  16. DeedWest

    DeedWest 2010 Roadster 2.0 - VIN 523

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    For those who have Debug Mode active, you can watch battery temperatures to gauge when the A/C will divert to cooling the pack. In the 2.0/2.5, it kicks on around 41C & brings the pack down to 38C before returning to normal.
     
  17. gregd

    gregd Active Member

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    Update on my car, for documentation purposes... Finally got it to the SC for troubleshooting and repair, and they confirmed it was slightly overfilled - 820 grams instead of 800. Refilled properly, and it seems to be working the way it should.
     
    • Informative x 1
  18. MLAUTO

    MLAUTO Member

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    Lets hope you have a 2.5. According to the underwood sticker, 1.5's take 700g, 2.0's take 720g, and 2.5's take 800g. And the owners manual states 725g except the 2.5 addendum states 800g..
     
  19. gregd

    gregd Active Member

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    #19 gregd, Jun 14, 2018
    Last edited: Jun 14, 2018
    Yeah, I'm wondering about that too. The car is a 2.0, not a 2.5. Just got it home, and the pressure when charging is right up there at 22 bar, just as before. SEEMS to be cooling ok (they did a 70 amp charge after a spirited test drive, and it cooled right down), no alerts.

    On the phone with them now...

    EDIT: The manager will call me back later, but in the mean time, I looked under the hood. It clearly says 800g R-134a. Maybe I've got a mutt for a car? At one time, the prior owner swapped out the front and rear fascia pieces for the 2.5 style, but left the dash as original.

    Pressure after charge with 800g.jpg AC-sticker.jpg

    Will report back after I hear more from them...
     
    • Informative x 1
  20. MLAUTO

    MLAUTO Member

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    They probably needed to add more refrigerant for the battery cooling, and changed the amount to 800g. The 2.0 I have was salvaged with 1500 mi and has never been serviced, so the sticker shows 720g. 40C (104F) outside is really hot, and the 22.6 bar is towards the very top of acceptable at that temp, but as long as it does not overheat and shut down you should be OK. Check it when the outside temp is at around 90F (32C), and it should be a lot lower. You really need to check it while driving, as those little fans and stagnant garage air will mess with the pressures.
     

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