TSB: Replacing Electric Passenger Compartment Heater (WSD8) - April 17, 2025

[Tooney]

Porsche is monitoring vehicle analysis logs for heater failures occurring in the newer "optimized" heaters that were installed to replace the previously "unoptimized" heaters (manufactured prior to Feb. 14, 2023) that failed. (The optimized heaters were installed during heater replacement campaign WPL8 which started in October, 2023, and in later built Taycans.)

Note that all Taycan model years including 2024 and 2025 are included.

https://static.nhtsa.gov/odi/tsbs/2025/MC-11017927-0001.pdf
Edited on May 8, 2025 to add link to Porsche intranet posting: https://static.nhtsa.gov/odi/tsbs/2025/MC-11018121-0001.pdf
Edited to add link to revised TSB dated Nov. 25, 2025: https://static.nhtsa.gov/odi/tsbs/2025/MC-11026400-0001.pdf This TSB adds scope for partial refill of the cooling system when heater is replaced for some VINs, to previous scope of completely refilling cooling system.
Edited to add link to updated TSB dated Dec. 15, 2025: https://static.nhtsa.gov/odi/tsbs/2026/MC-11027242-0001.pdf
EDIT: updated TSB dated Mar 3, 2026: https://static.nhtsa.gov/odi/tsbs/2026/MC-11030798-0001.pdf

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[chun]

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You’d think the 2nd time they would do more testing to make sure it’s not breaking again.

I guess not

 

[rim23]

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[Dee]

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You’d think the 2nd time they would do more testing to make sure it’s not breaking again.

I guess not

We're all testing it.
Didn't you know? ?

 

[whitex]

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You’d think the 2nd time they would do more testing to make sure it’s not breaking again.

I guess not

They are testing, on customer cars. What better test than to install it on a few thousands cars and watch it via over-the-air telemetry. True real-world test for environments where Taycan customers drive and how they use the heater. Of course this is very expensive testing. I'm curious what the cost split of this is between Porsche and heater supplier.

Could they have done it cheaper by doing some sort of highly accelerated life testing? I suspect someone decided to take a chance on a small changes mitigation idea without thorough testing, but it didn't work out as planned. Small changes might just be updated firmware, or added heat shielding/spreading, but no redesign of the board or substituting a different IC. I'm sure the tiered supplier system is making this a logistics nightmare.

 

[W1NGE]

Porsche don't make this component remember and so the manufacturer/ supplier (Webasto) should be redoubling efforts to ensure a reliable HV heater.

 

[whitex]

Porsche don't make this component remember and so the manufacturer/ supplier (Webasto) should be redoubling efforts to ensure a reliable HV heater.

Yea, but depending on the contract, they may or may not be paying Porsche for total replacement costs (could be just replacement parts). I suspect OTA monitoring costs are all on Porsche too.

 

[Fish Fingers]

The original failed heaters was a major issue for a number of years and gave the Taycan so much bad publicity and contributed greatly to its unreliable status.

I am shocked that they didn't get it right with the new improved version.

 

[whitex]

The original failed heaters was a major issue for a number of years and gave the Taycan so much bad publicity and contributed greatly to its unreliable status.

I am shocked that they didn't get it right with the new improved version.

My speculation, nobody wanted to pay for a redesign (which involves not just money, but also time), so they green lit some mitigation proposed by the heater manufacturer instead. Businesses have to take risks, not all of them work out.

As an engineer I would love to have seen the root cause investigation results of the original failure, the available mitigation options, and how they arrived at the one they chose. I doubt I will ever get to see it, though it is not completely out of the realm of possibilities. I have worked with engineers in other automotive manufacturers, so maybe one day I will work with someone had worked at Porsche who can shed some lights on this over some dinner and drinks while working on a completely different project (possibly different company too). Such things have in fact happened to me during my career occasionally. One of the most shocking ones was I found out that a technical decision on a project I worked on years earlier, which I could not understand at the time, turned out to be internal politics between customer's VPs. Once the PM filled me in, it finally all made sense why the customer chose the most difficult and least likely to succeed option for a collaboration project I was leading.

 

[Tooney]

Revised TSB dated Nov. 25, 2025: https://static.nhtsa.gov/odi/tsbs/2025/MC-11026400-0001.pdf This TSB adds scope for partial refill of the cooling system when heater is replaced for some VINs, to previous scope of completely refilling cooling system.

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