Tesla provides new details on heat pump issues in NHTSA recall document

For the last few months Tesla owners around the world have been seeing their heat pumps fail, leaving them with no heat in extreme cold temperatures.

Tesla has been largely quiet on the issue, with the exception of a few comments by CEO Elon Musk saying the problem could be related to a heat pump expansion valve.

Since the issue surfaced, Transport Canada and the U.S. National Highway Traffic Safety Administration (NHTSA) have launched investigations over concerns of poor windshield defrost performance resulting in a lack of visibility.

Today the NHTSA posted a recall notice (SB-22-18-002), in which for the first time Tesla explains in detail what they believe was the root cause.

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 operating 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 notice goes on to say that “out of an abundance of caution”, the affected vehicle population was expanded to include vehicles that have not yet updated to 2021.44.30.7.

Tesla estimates that just 1% of the 26,681, or 266 vehicles identified suffer from the defect. This number seems low considering Transport Canada alone had received 171 complaints as of last week.

Based on the notice, it appears Tesla believes 2021.44.30.7 fixes the issue, but we have still been receiving reports of owners on the latest software version experiencing heat pump failures, even after visits to a Service Center.

Drive Tesla has reached out to Transport Canada for an update on their investigation, but have not received a reply by the time of publication. No similar recall notice has been published to their website.

UPDATE 4:10pm PST: Transport Canada has confirmed with Drive Tesla that a similar recall will be issued soon. You can read more here.

You can read the full recall notice below.

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