A/C issue and possibly defogging issues

[Bijli123]

Hi Everyone,
I had a 90D long back, which I had to lease transfer when I moved from Seattle to Vancouver.

Recently got a Raven 100D. New car is a huge improvement compared to the older car. Especially the suspension is much better.

I am however facing two issues which I haven't faced with my earlier MX or with any other car:
1. When I am in Auto climate control, many times the car doesn't use A/C. It instead uses keep using higher fan speed - which doesn't help with outside temperature is higher than what I have the HVAC set at. This leads to ineffective air conditioning and much higher noise in the cabin.

2. This issue is a more critical issue. I was driving today on the highway and it was raining. Climate control was in Auto and likely not using A/C. I had set the car to 21c (70F) and outside was 19c (66F). I was an auto climate control and likely that had the A/C off. I felt some fog building up and turned on the defogger/defroster in red mode. Immediately the windshield became fogged from the inside and I couldn't see anything outside. It was a very scary experience and we somehow stopped the car in a safe location and started again once the fog cleared.

Is it possible that these two issues are related.

So my question are:
1. Is it normal for the auto climate control to be aggressive with not using A/C and instead keep using higher fan speed (when it isn't even helping and might be making matters worse). Or is it possible that there is some issue with the air conditioning system.

2. Fog on the inside on the windshield is one of my worst nightmares. What settings should I use to avoid it. I read up a bit and seem to have gathered following tips:
a. Use the blue defogger when it's raining and colder than 21c (70f).
b. If a isn't working, make sure the A/C is on, recirculation is off and temperature in the cabin is higher.

Really appreciate your help.

Thanks

 

[mxnym]

This doesn't sound normal to me, but perhaps you have range mode on and it has implications like these. If you have range mode on, I'd advise turning it off.

 

[Bijli123]

Thanks. I checked for range mode and it wasn't on.

I tried a few other things. I set the temperature to LO an the cabin would start cooling immediately. Then I set the temperature to HI and it was minutes before the cabin started feeling lukewarm.

Is this normal?

 

[Joelgjr]

We have the opposite problem - it uses the AC too often. When I used to live in Boston it would put the AC on if it was any temperature warmer than 35F. I would always manually turn it off.

 

[mxnym]

Thanks. I checked for range mode and it wasn't on.

I tried a few other things. I set the temperature to LO an the cabin would start cooling immediately. Then I set the temperature to HI and it was minutes before the cabin started feeling lukewarm.

Is this normal?

Doesn't sound normal to me, but I don't have a brand new Raven. Historically speaking, cooling should require more time as gas has to be compressed and moved and stuff while heat is just a PTC element, which should be pretty much instantaneous. That having been said, I believe they added a heat pump to the Model Y. In that case, they might have ported that over to the Model X later on, which could make heat take longer. Unfortunately, if HI and LO ultimately give you hot and cold air, there is a non-zero chance that the service center is going to tell you it's normal whether it is or not.

 

[Bijli123]

I schedule an appointment. Let's see how it goes.

 

[wreighven]

Item 1 sounds a bit like what mine was doing. Was a quick fix at the SC; in my case it was a bad “evaporator temperature sensor.” Now my fab doesn’t blow nearly as loudly and it is MUCH colder. Yay.

 

[Paul42]

I schedule an appointment. Let's see how it goes.

Did you get any resolution from your appointment? I'd love to hear what they told you.

We were recently driving over Bluett Pass in our S when like you, our windows fogged up completely and we had to pull over. Playing with the HVAC controls to see if we could find a more efficient defog setting, we noticed that it would force the air to recirc if we turned the fan above speed 8 or 9. It is not a very efficient system.

Anyway, we took our car in to the Renton service center, and we just heard back that everything is supposedly operating normally.

 

[Bijli123]

I had the same issue as @wreighven - "EVAP TEMPERATURE SENSOR" - which was replaced. Took two visits to fix it.

Normally we wouldn't need to know details of such basic operations of vehicles, but with Tesla you never know. I have never faced this issue with 10+ cars I have owned and sadly issues like these happen with Tesla.

I did a bunch of research and figure following out. Hope it helps!

Why do we get fog on the windshield
This fog is humidity in breath of people and pets inside the car. Also food, if you have been eating in the car. If the humidity in the car gets too high, it tends to condense on the coolest part of car, which is usually windshield or side windows. It also hurts if you have recirculation on, because it traps humidity within the car.

What can cause you to still have this issue
1. If the Evap sensor is defective - your A/C doesn't even work. It took us two visits to get this fixed.
2. If you set temperature to below 22 - was in my service notes.
3. If you are in manual mode which has A/C off. Usually your car will show a warning in the main screen saying "Defogging limited due to settings". Recirculation on makes it worse in this situation.

How to avoid it
Make sure that the A/C is on. A/C removes moisture from the air. Problem solved. In rainy conditions, start the blue defogger mode for a few minutes before you start your trip.

How to avoid it - detailed
1. If you are waiting in car and eating food - make sure your A/C is on.
2. If you are driving in rainy conditions - take action before it becomes a problem: Press the defogger button to the blue mode, when you start your car. This maintains your temperature while using A/C to defog. If somehow this isn't working - set manual mode which A/C on and air going to windshield and disable recirculation. Red mode - is for removing ice outside the windshield and is called defroster mode.
3. If your A/C is not working - tough luck. None of steps above will work. But you still have one option, which is also the option you should use in worst case situation. Open windows. You will be cold, but mixing outside air reduces humidity. This is a bit unintuitive to bring high humidity cold air from outside - but read up about relative humidity. Cold air can hold less moisture. So when the warm air with high humidity from within the car gets colder at windshield - it can't hold much water and rest of the water condenses. But opening windows - you are mixing with outside air causing the extra humidity inside the car to go away. Same reason why in winter, outside air at 36F at 95% humidity becomes 20% humidity at 70F - leading to dry air inside the house.

What to do when you are getting fog on your windshield while driving
If your A/C is working and you didn't manually stop A/C - you shouldn't be facing this. If you do face this situation, do not press the defogger button to go to defogger mode (blue) or defroster mode (red). It will just force all the high humidity air on the windshield making it go opaque immediately.
Steps to take in this situation:
1. Try to stop on the side if possible.
2. If somehow A/C was off, switch it on right away. Make sure your air is not pointed to the windshield at this point.
3. Open the windows

This is a really scary situation and hope this information helps. I am still worried about this and hopefully we don't face this issue going forward.