Back in chilly January, we reported that the National Highway Traffic Safety Administration (NHTSA) and Transport Canada were investigating allegations of Tesla heat pumps failing in cold conditions. Now, they seem to have gotten to the bottom of it and Tesla is issuing a recall on 26,681 vehicles.
That includes certain 2021-2022 Model 3, Model S, and Model X vehicles, as well as certain 2020-2022 Model Ys because they do not comply with FMVSS 103, S4.4 in the highway code. Fortunately for Tesla customers, the automaker believes the root of the problem lies in software, so an update may be able to prevent the issue from occurring again.
The cause of the issue, per NHTSA documents, was an electronic expansion valve that experienced controller communication interruptions causing its driver to realign. Over time, an accumulation of interruptions and realignments could cause the electronic expansion valve to open unintentionally and trap refrigerant inside the evaporator. That could deplete the refrigerant from active components in the system and lead to a fail-safe compressor stoppage.
The result is a loss of cabin heating, particularly in temperatures of -10°C (14°F) and a message in the user interface that the HVAC system is unavailable. While that’s deeply annoying for the passengers, it could also be dangerous since it affects the defroster’s ability to clear the windshield.
For owners, meanwhile, it was a cause for concern. One Canadian customer reports having been without heating for a month and experiencing “buyer’s remorse.”
Firmware published after release 2021.44.30.7 should prevent the issue from happening anymore by introducing a software command to close the electronic expansion valve and preventing refrigerant from entering the evaporator. Vehicles whose HVAC systems have experienced issues should still be under warranty.
Well @elonmusk having some buyers remorse. Last Feb had our Model Y in the SC for a month with no heat. New Super-manifold and thought it was fixed. New set of sensors last week and now this. -30c in #Saskatchewan and a very cold 1 hr drive later we barely made the supercharger pic.twitter.com/JLJ7Pmzc0P
— Mark Kroeker (@paateach) December 28, 2021