Me: "Defroster on please!" Car: "No."

[jsmay311]

I recently got a 2023 Model 3 (with a heat pump) after driving a 2018 Model 3 (with a PTC heater) for 5 years, and I can't figure out wth is going on with the defrost/defog controls in the 2023.

If I try to turn on defrost to get some hot air on the windshield, within seconds the car turns off defrost and switches to just blasting cold air in my face at max fan speed.

My 2018 never behaved like this and I can't find anything online or in the manual that explains this behavior. Can anyone help me understand wtf is going on here?

 

[fhteagle]

What firmware version are you on?

 

[jsmay311]

What firmware version are you on?

2023.32.100

 

[DrChaos]

Your temperature is set for max-cooling LO, which will override automatic settings generally.

It can't do that and heat the windshield. Set interior temp to 72 and try again. Do a reboot too.

 

[jsmay311]

Your temperature is set for max-cooling LO, which will override automatic settings generally.

It can't do that and heat the windshield. Set interior temp to 72 and try again. Do a reboot too.

That's not it.

It's done this every time I've tried using defrost (maybe 4-5 times over the past month) regardless of the temperature setting. And last night I even tried increasing the target temperature right after taking that video to see if it would have any effect, and it didn't. Defrost still turned itself off right away even with the temp set to 70F. Which shouldn't be surprising since turning on Defrost overrides the previous target temperature and changes it to HI, so it should be irrelevant.

Despite the above, I just took the car out for a quick spin to triple check if the target temp had any impact, and I started with in in LO-manual like I normally have it set, and Defrost did NOT turn off right away, for the first time ever. That at least confirms that the target temperature isn't the issue, but now this has me wondering what was different between just now and every other time I've tried using Defrost. Maybe something with a humidity sensor and the humidity level inside the car since this was the first time I tried turning on Defrost without actually needing it to clear up the windshield? Idk.

 

[DrChaos]

That's not it.

It's done this every time I've tried using defrost (maybe 4-5 times over the past month) regardless of the temperature setting. And last night I even tried increasing the target temperature right after taking that video to see if it would have any effect, and it didn't. Defrost still turned itself off right away even with the temp set to 70F. Which shouldn't be surprising since turning on Defrost overrides the previous target temperature and changes it to HI, so it should be irrelevant.

Can you start at 70 and Auto and see if it works then? Maybe there is a difference between starting from auto and manual, I usually use auto.

Despite the above, I just took the car out for a quick spin to triple check if the target temp had any impact, and I started with in in LO-manual like I normally have it set, and Defrost did NOT turn off right away, for the first time ever. That at least confirms that the target temperature isn't the issue, but now this has me wondering what was different between just now and every other time I've tried using Defrost. Maybe something with a humidity sensor and the humidity level inside the car since this was the first time I tried turning on Defrost without actually needing it to clear up the windshield? Idk.

OK, that's strange then. Did the single-tap Blue Defog mode work? Or maybe the system is too clever for its own good now and uses weather forecasts/external temperature? Maybe if the external temperature is too far above freezing it shuts off the red defrost on assumption the user made a mistake? Or maybe as you think if the humidity is high enough it wants you to use the Blue Defog mode? Or maybve you have to be driving long enough for there to be some heat in the system that it can use?

Or maybe it's just a defect with your car and it's reverting because some part of the cooling system isn't operating properly, maybe a busted sensor that's needed for this mode?

Can you set to maximum heat on manual, and direct heat only to the windshield?

 

[jsmay311]

I did more fiddling the last couple days. Sometimes it stays on defrost, sometimes it quickly switches from defrost to defog, and sometimes it quickly turns off defrost/defog altogether (like in the original post). I haven’t been able to decipher any pattern between the behavior and the temperature setting or auto/manual.

I’m assuming the root cause of this is the usual case of Tesla thinking they can make the car smarter than the driver and therefore justify overriding whatever the driver wants, and then predictably doing a poor job of it.

Maybe I should submit a service ticket and see if I can learn anything that way. But I’m pessimistic anything productive would come out of it.

 

[DrChaos]

I did more fiddling the last couple days. Sometimes it stays on defrost, sometimes it quickly switches from defrost to defog, and sometimes it quickly turns off defrost/defog altogether (like in the original post). I haven’t been able to decipher any pattern between the behavior and the temperature setting or auto/manual.

I’m assuming the root cause of this is the usual case of Tesla thinking they can make the car smarter than the driver and therefore justify overriding whatever the driver wants, and then predictably doing a poor job of it.

Maybe I should submit a service ticket and see if I can learn anything that way. But I’m pessimistic anything productive would come out of it.

Do some videos and attach to service ticket. I suspect a defect more now.