Thermostat module or resistor??

I have a 2005 TRD sport with around 158k on the. Problem is last 3 summers we have had to replace the thermostat module (I believe its called that). A/C only works on high when this thing goes bad. I can see one of the metal connectors looks burnt. Last summer he replaced the harness, spliced the harness into the module using heat shrink wrap This summer he only replaced the module. I still have the wiring in my glove box.
Any reason this keeps going bad and should he replace the harness too.
Advance auto said they didn’t sell the harness, just a module for 30 plus dollars. I think last years came from EBay which had the harness. Anyway we have replaced the thermostat resistor?? or module 3 summer. Do I have a bigger issue causing these to burn out?

 

You mean the Blower Resistor?

 

There is an updated blower resistor and connector.
I will add a link below.

You need to check 3 places to ensure good connections too.
The actual control panel (switch)
The resistor
And the connection at the blower motor.

If any of the connections look burnt. Replace them.
Poor connections cause more resistance.

Part #’s and diagrams to updated resistor
https://www.tacomaworld.com/threads/2nd-gen-information-diagnostics.784008/#post-28042158

 

You might also check the cabin filter.
Anything that restricts airflow can cause the motor to work harder.
Which strains the resistor even more. (Unless it’s on high speed, then it sends it all through the switch)

 

Could possibly have a bad blower motor
drawing to many amps ..that’s if all the wiring looks good

 

Visually check the A/C selection panel rear, wire and connector of the harness that connects towards the blower resistor.

 

That’s a possibility too.

 

Thanks. I got the supposedly upgraded module and harness. Every time we have replaced it there is a burnt connector or whatever the part is called. This last blower motor resistor is a Toyota part from EBay still in packaging and cost way more than the other past 2 from eBay. The strange thing is previous 2 summers when the resistor went out and blew only on high as it’s supposed to, it is not putting out cold A/C air. Even though the other ones went bad they still put out cool air.
Also A/C air was good until now. I tried checking the Freon level, but the condenser wouldn’t kick on to let me know if I need Freon. Is the air compressor not kicking it keeping me from being able to get a gauge reading? I wasn’t expecting the A/C air not to be cool on high like it’s done before. I think I’ve used non Toyota parts last 3 times. Maybe this one from Toyota will work. The module looks sturdier and better quality than the hundreds of non Toyota ones out there.

 

The resistor going bad only affects the speed your blower motor runs - not the temperature of the air it moves. The lack of cold air is a separate problem.

 

Too low on R134A is causing the compressor to not turn on. Take it to a shop with the correct tools and training and they will tell you what is wrong for sure.