Installing OEM Heated Seats in SR5 need help

[Toyota4WD]

Hello All - I’m a new 4Runner owner and am looking to retrofit OEM heated seats rather than installing an aftermarket solution. I’ve subscribed to Toyota TIS and have been reviewing the factory wiring diagrams and system operation for the heated seats. Based on my research, this retrofit should be feasible, as the SR5 trim includes heated seats as standard equipment on Canadian-market vehicles.


The main point where I’m running into uncertainty is whether the A/C Amplifier Assembly needs to be replaced. I have not been able to find any explicit reference in the repair manual indicating that a different A/C Amplifier is required solely to add heated seats. No other HVAC changes are planned—the vehicle will remain single-zone, non-automatic climate control (no auto or dual-zone functionality).


From what I can see, the heated seat switch inputs route through the A/C Amplifier Assembly via the No. 2 A/C Control Assembly. Can anyone confirm whether the existing A/C Amplifier supports these inputs, or if a different A/C Amplifier Assembly is required for proper OEM heated seat operation?

What I have done so far:
- Replaced my No.2 A/C Control Assembly (w/heated seat switches) with one from a wrecked 2024 Tacoma
- Did some discovery work and found the two plugs under each seat to be prewired from the A/C Amplifier to the seat
- Ordered the Heated Seat Sub Assemblies
- Ordered the OEM Heated Seat Elements for the seat bottoms (waiting for these to come in)
- Bought some used seatbacks from a wrecked 2024 Tacoma and pulled the pads out and put them in my 4runner seatbacks
- Made my own seat harnesses with factory connectors/terminals and wired up the Heated Seat sub assemblies

All required components are currently installed and ready; I am only waiting on the seat bottom cushions to arrive from the dealer to complete the installation. At this point, my main concern is whether the heated seat switches will function as intended once everything is connected.

Specifically, I am looking for confirmation regarding the A/C Amplifier Assembly and its role in the heated seat system. Clarification on whether the existing A/C Amplifier will support the heated seat switch inputs would be very helpful.

Once functionality is verified, I plan to document the process and publish a detailed how-to guide, including applicable part numbers.

TIA

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[TyRoosevelt]

I have no idea on how to help you but what you are doing is pretty awesome. Please attach lots of pictures and explain how you removed that climate control. It will help a lot of other people.

 

[Toyota4WD]

I have no idea on how to help you but what you are doing is pretty awesome. Please attach lots of pictures and explain how you removed that climate control. It will help a lot of other people.

I will definitely do that. Removing the climate control assembly required several steps, including removal of the center console and multiple trim panels surrounding the console. Once everything is fully functional and verified, I will need to disassemble the components again in order to document the process and capture detailed photos of the procedure.


Update – A/C Amplifier Findings


I have some good news and some bad news after discovering a document in the Repair Manual I missed.

The Repair Manual identifies two different A/C Amplifier Assemblies: Type A and Type B. Type A uses five connectors, while Type B uses three connectors. The two additional connectors shown on the Type A diagram are K34 and K35. These connectors are dedicated exclusively to heated and climate-controlled seat functions for both the front and rear seats.

After lowering and inspecting my vehicle’s A/C Amplifier, I confirmed that the SR5 is equipped with the Type B A/C Amplifier Assembly. Unfortunately, this means the existing amplifier does not support heated seats. As a result, the A/C Amplifier must be replaced with the Type A unit, which is approximately $1,200 (after discounts I paid $930 with Tax, at this point I’m too invested to turn back)—this is the bad news.

The good news is that connectors K34 and K35 are already present in the vehicle harness. They are prewired from the factory and taped back.

I contacted my Toyota dealer’s parts department yesterday, provided a Canadian-market SR5 VIN for verification, and ordered the correct A/C Amplifier Assembly (at this point, I’m too invested to turn back). Once the new amplifier is installed and everything is reassembled, I will provide another update.

I have thoroughly reviewed the Repair Manual and have not been able to determine whether the new A/C Amplifier Assembly will require programming or initialization using a scan tool after installation. The Repair Manual only provides removal and installation procedures, with no reference to any calibration, initialization, or programming steps.

I am not sure if we have a Toyota technician active on the forum, but if anyone can confirm whether programming or initialization is required after replacement, that information would be greatly appreciated.

 

[Maximus4R]

This is super interesting, following along for sure. Once you’re down with this project can you figure out how to add dual climate to my ORP? Haha.

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