Pre 98 to 98-00 hvac control module swap

A simple mod for those who want to change their HVAC Controls from pre 98 to 98-00. I believe this mod can also be reversed for those who want pre 98 hvac controls.



Tools needed:

Phillips screwdriver

Soldering iron

Flat-head screwdriver

Mini flat head driver set or depinning tool kit

10mm socket (optional in my T100 but makes it easier to route the cables.)



Notes: My reasoning to solder might be due to a previous wiring issue I refuse to track but I bridge pins 3-4 (didn't want to jump the wires themselves). You must swap original cables to their corresponding new controls (might only be me because I'm in a T100 and the cables are longer).



Although both harnesses are identical the pinout itself is inverse as shown in the pinout diagrams below:


1997 Toyota T100 Blower Speed Control Pinout



1998-00 Toyota Tacoma Blower Speed Control Pinout









As we can see both although the harness is identical the pins themselves are inverse. To do this we must match the new wiring by changing them to the new pinout configuration. Below are the wiring diagrams for both pre and the updated HVAC modules:


1997 Toyota T100



1995-1996 Tacoma




1997-1998 Tacoma



2000 Tacoma






To begin we must first disconnect the battery and 15AMP fuse before removing the HVAC module.

Once disconnected from power the next thing to do is to remove the four cables whose locations can be seen in the pictures below. One is located in the engine compartment and the other three are inside the cab. For the Tacoma owners it's pretty straightforward with a quick tutorial if help is needed https://www.youtube.com/watch?v=oFFvmAkgol0 (credit to youtuber Tyler R).

https://www.youtube.com/watch?v=l_ikLUtHRW0 (credit to youtuber Stupid Endeavors) This video also showcases how to remove the cables in order to keep your original ones. Note: The way he removed the AC harness is incorrect, you first want to remove the AC Switch then insert a flathead into a pin directly inside. It will pop straight down.


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For T100 Owners


Remove the cover then the stereo using the phillips screwdriver (4 screws).



Once the stereo is out unscrew the 3 phillips screws similar to the tacoma.

Extract the AC Switch and press the AC harness down with a flathead. This should pop it straight down. Unplug the heater fan control identical to the Tacoma as well as this plug(I needed to let remove it from its attached position to connect it to the rest of the harness):




Now you can pull the Module out and repin your harness.

This is what mine looks like with the blue/red (needs to be pin 3) and blue/green (needs to be pin 2) ultimately changed per the diagram.



Once complete you should be able to plug it in and it should work but in my case I wasn’t getting any lights to the dash so I needed to either jump pins 3-4 (red/blue wire and yellow/green wire). I didn’t want to mess with the wires so I removed the integrated heater fan control and soldered pins 3 and 4 together internally. From there you just do the reverse to put it back together and reconnect the battery and fuse.