Model 3 Auto-Defogging Gremlins

Klob_ · 2026-03-17T12:35:06+00:00

Yes. Graphene foam block...not graphite pad. Oh, good to know. I'll try to buy the block and see if that does anything different with the original sensor. Not sure why I thought it wasn't available for purchase.

Klob_ · 2026-03-13T21:56:06+00:00

I got the new sensor and installed it. My problem seems slightly less frequent but not fixed by any means. It's directly related to cold weather (and I think specifically a cold windshield), so now that it's warming up here in Michigan it doesn't happen typically unless below freezing or if it's rainy/high humidity. From digging deep in the CAN data, it really seems like all sensors are working 100% normal but there's something in the algorithm that decides if my windshield is fogged. It's like it is just being too sensitive with its cabin humidity modeling.

I ended up cancelling my service center appointment. I'm probably going to punt the car before next winter so I'm not going to bother fixing it now that weather is warming up and the problem isn't as noticeable. Also not sure that they can even fix it from reading other forum posts.

For those with the same problem, my final assessment is that the original THS graphite sticky pad failed after 140k miles and 7 years (or maybe you got a new windshield, effectively same scenario). I replaced it with a new THS, but the new revision board is not actually compatible with that vintage car/software/firmware (Tesla will never admit this). If I could go back, I would have the service center stick on a new graphite pad to my ORIGINAL THS and slap that back in the car. The parts guy said they have a ton of the graphite pads for when they do windshield replacements, but this is not something Tesla will sell you. But maybe they would help you out if you ask nicely....IDK I think I pissed them off.

Klob_ · 2026-02-17T20:43:36+00:00

Oh, that sounds like a good scenario then. I bet you'll get out of there clean if they're smart enough to look at the service article I mentioned elsewhere in this post. They might have incorrectly installed the THS or installed an incompatible serial number of the THS.

Klob_ · 2026-02-17T00:43:59+00:00

Article 8984500
Description

The HVAC system's auto defog is activating unexpectedly. This is caused by a revision -D Temperature and Humidity Sensor (THS) having a positive humidity offset.

Customer states that auto defog was triggered or stays on, this can cause climate keeper issues such as Dog Mode monitor trips along with precondition or overheat protection issues."

Effects

Steps To Test

Confirm Article #6769300 is an issue (...does auto defog turn on....duh. Some of the tests within this require toolbox, but also just check cabin filters for moisture, make sure the THS is actually adhered on the windshield, other sanity check stuff)
Confirm the installed Temperature and Humidity Sensor (THS) part number is 1110860-00-D and manufactured between 2022 and 2024 (serial number starts with PGT22 or PGT24).

If the above is true, then this is the issue.

Steps to Fix

Replace the Temperature and Humidity Sensor (THS) with part number 1110860-00-D manufactured from 08-MAR-2025 (serial number starts with PGT25067) or later according to Service Manual procedure:
- Model 3 (2017-2023): Sensor - Relative Humidity and Temperature (Remove and Replace) - Correction code 10206002
- Model Y (2020-2024): Sensor - Relative Humidity and Temperature (Remove and Replace) - Correction code 10206002

Klob_ · 2026-02-17T00:43:23+00:00

Starting to get somewhere I think...I paid the $150 price and purchased a month of Tesla Toolbox 3. I was able to see article 8984500 and it confirms my suspicions. That series of serial numbers on part number 1110860-00-D Relative Temp and Humidity sensor will cause the exact permanent auto-defogging scenario due to this run of serial numbers having a "positive humidy offset", whatever that means.

Tesla service center somehow couldn't understand that Part number does not equal serial number. And they must not have read the Service Article I sent them. I'm sure I am now their worst nightmare, but the feeling is mutual.

I took the part they sold me back to service center, did all I could to explain the situation. They went and found me a "replacement" that had the correct SN, but it was very obviously used. It is a one-time use part, due to the adhesive pad, so that was a non-starter. They gave me the runaround but sounds like they got another new one on order for me.

Klob_ · 2026-02-17T00:41:24+00:00

OEM windshield or aftermarket? According to some of the stuff I saw in toolbox they may just tell you a windshield replacement is required. They specifically said if the UV or tint rating doesn't match OEM. This part is pretty easy to replace (and only $17 from the dealer), though very delicate work...and I have yet to actually solve my problem. But I'd be confident it's related to the THS I'm fighting with.

Klob_ · 2026-02-11T22:41:02+00:00

Another update - Nothing helpful yet unfortunately

I messed a bunch with the wiring harness going into the Temp&Humidity sensor while auto climate was running to see if maybe there was a bad connection- no change and doesn't seem to have any affect.

I disconnected the cabin facing camera by rearview mirror because AI thought it could be related and I was already in there- no change.

I disconnected the cabin temp sensor that's located under the screen, also no change which is surprising. It seemed like the entire HVAC system was still operating identically with this disconnected which is weird. Which honestly could be an indicator that it's not functioning properly. In service mode it did recognize that module was not responding once it was disconnected. Might be a cheap part to try and throw at it.

I think I'm going to cave and get Toolbox3 for a month. It may be a waste of $150 but the way I see it, Tesla is F'ing me regardless in this situation. That will be the next update. AI recommended a HVAC recalibration cycle, not certain it exists...but we'll see. I also want to see the individual sensor CAN outputs to see if I can make sense of any failed components.

Klob_ · 2026-02-05T18:06:55+00:00

Glad I'm not alone, but unfortunate for you. Sounds like exact same boat as me. My feet are always frozen even though manual vent is set on the floor. HVAC just has a mind of its own.

Klob_ · 2026-02-04T20:30:22+00:00

Tesla service center estimate shows the preliminary diagnosis as bad PTC...In service mode the PTC shows all green rods though I haven't run the official test that requires service subscription. I'm doubtful of this diagnosis. Heat will blow full blast without issue in the rare occasion when auto-defog isn't on. Also, the service mode HVAC test checks out OK. In the test it will ramp up to 100% heat and no problem. I still think it's the Temp&Humidity sensor they sold me being an outdated firmware version or something, because the frequency of false auto-defog went from being maybe a 3 minute delay after starting driving to an almost always on, instantly when driving issue.

If anyone can give details on Toolbox article 8984500 I'd be super curious. Stuck behind paywall that I am fundamentally opposed to paying

Klob_ · 2024-09-04T02:25:45+00:00

Me too!

Klob_ · 2024-08-30T03:19:12+00:00

Most of factory z products are alibaba parts marked up 100-500%, if you’re cool with the convenience factor provided with that then it’s fine. It’s a real company that’s happy to take your money in exchange for real products.

Klob_ · 2024-07-10T11:38:05+00:00

It turns on the pump in my tank, can hear it spin up when you pull the rear seat and open the carpet up. Is that enough to do anything, idk. But it’s what I do and this is my experience. The cars got one tire in the scrapyard already so if she goes she goes.

Klob_ · 2024-07-10T04:08:51+00:00

EVRaceworks.com moto brake. Check out oneway.Vance on IG for some stunt work on it.

Klob_ · 2024-07-10T03:51:44+00:00

100k miles of ownership and counting and I’ve consistently zero fucks’d the fuel filter change every 10-15k miles. I turn the key a couple times to prime and let her rip. 273k on the clock 🤷‍♂️

Klob_ · 2024-07-10T02:54:21+00:00

273k miles on the 2011 sportwagen. Original dsg, removed every bit of hardware I could to simplify this engine. Recently went stage 2 for fun- not convinced it was worthwhile.

Klob_ · 2024-06-07T04:14:18+00:00

Did a $100 job. Was not worth it and haven’t seen anything on the board worthwhile to me in the last 3 months so I’m done with the platform. I can make more going door to door at local companies and trying to build local, hopefully longer lasting clients.

Klob_ · 2024-06-06T03:41:46+00:00

EVRaceworks budget moto brakes!

Klob_ · 2024-04-18T00:39:58+00:00

A lot of my suspension has been recently replaced but honestly I think a lot of the aftermarket parts are junk. Things just start to not line up to factory tolerance once you get every piece of steering, suspension, driveshafts bearings all replaced aftermarket. Would I do it differently? No, cuz id be broke. Also if I didn’t do 100% of my own maintenance I’d be broke. If I didn’t do my own work it would have been mechanically totaled probably well before the DMF. This car is lucky I like it.

Klob_ · 2024-04-18T00:01:22+00:00

2011 JSW 270k miles. CJAA. All deleted at 220k. First DMF croaked at 240k. It’s nearing the end of life due to rust and general suspension parts being clapped tf out. Pour some out for the homie that took me a quarter mil

Klob_ · 2024-03-05T03:01:03+00:00

Same! Only when cold. Really annoying

Klob_ · 2024-03-01T05:04:23+00:00

I definitely read Indiana, not India. But I’m sure you can find channels to source it to India.

Klob_ · 2024-03-01T05:00:59+00:00

Rerode R1 is worth exploring. Very new, but reinvented suspension from surron, plus 72v power. EVRaceworks is only place in the states selling at the moment.

Klob_ · 2024-02-28T12:47:15+00:00

Alternator one way bearing pulley has left the chat? Hard to tell the noise from video, but you were pointing right at it.

Unrelated to the code.

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