NHTSA Issues Safety Recall over Heat Pumps
This just in: Cold weather sucks. Not surprising of course, no one likes to be cold, but as it turns out the extreme cold we’re experiencing this winter is causing big problems for Tesla’s heat pump system.
The problems started over a year ago when Tesla introduced a new heat pump system for the Model Y and newer Model 3s. For those who don’t know, up north it routinely gets so cold that having a heating system is a necessity; and when it breaks down, well that’s a health risk. But a software update reportedly fixed the issue… until this year.
Now this isn’t just a Tesla problem of course. Vehicles need to be specially engineered for operation in cold weather. Lots of systems fail when the temperatures dip below -15C, and in areas like Ottawa, Canada’s capital, the temperatures often drop to -30C and back up to the positives again. So it’s really no surprise that vehicles designed in California would need some iteration before adapting better to this sort of extreme temperature shift.
But what exactly is the problem? Well, according to the NHTSA recall notice, the Electronic Expansion Valve - a mechanism that controls the flow of refrigerant - sometimes has communication failures when it gets really cold. This leads to the system attempting to retry valve action, but it’s so cold that the valve gets stuck, forcing the system to go into fail-safe mode and stop heating entirely. Which, aside from making it really cold in the cabin, stops window defrosting, which is very dangerous.
Another software update rolled out quickly to fix the issue, but while it did alleviate a lot of the problems for many users, the stubborn valve problem seems to be persisting. CEO Elon Musk said that this issue is a high priority for Tesla, and they’re looking into possible hardware solutions as well
NHTSA explains the problem in detail in the new recall notice:
“In vehicles built with heat pump, the Electronic Expansion Valve (EXV) may experience controller communication interruptions, after which the EXV driver may attempt to realign the EXV rotor by rotating it in a small increment toward the open direction. When heat pump vehicles delivered with firmware release 2021.44 through 2021.44.30.6 experience such interruptions, the vehicle software does not close the valve, and the accumulation of interruptions and subsequent realignments over extended periods where the vehicle is awake may result in an unintended valve opening event. This, in turn, may trap refrigerant inside the evaporator and may deplete the refrigerant from the active components in the system. The depletion may result in fail-safe compressor stoppage, and cause loss of cabin heating, particularly in temperatures –10 C or colder. While the windshield defrost system continues to operate with the condition present, defrost performance may not fully comply with FMVSS 103.”
The recall makes sense, it’s just rough to have such a difficult problem crop up in the first full winter for these systems. But with the NTHSA and Transport Canada investigating the issue, as well as the Tesla engineers looking for hardware and software options; we’re likely going to see some iteration to fix things soon.