Issue with air mix temp with 1st Gen (2001)

Hi folks!

Super happy with my newer (to me) 2001. I was very lucky to get a 2.7L with great condition and about 100k on it.

However, I'm having an issue with my air temperature mix. Specifically, the hot/cold dial doesn't change the temperature reliably, often leaving the air mix very hot. I think the previous owner couldn't figure it out, either, because he had the entire A/C refreshed, but that isn't the problem.

I thought it was the air/mix servo and replaced it (https://www.tacomaworld.com/threads/06-air-mix-servo-stuck-no-heat-solved.454709/). It's certainly possible I did this wrong, but I can still get the air to come back to cold occasionally. The unit doesn't click anymore, but the problem persists.

This appears to be a common issue, but it's unclear how people solve it (https://www.tacomaworld.com/threads/climate-control-unit-replacement.714929/) Could it be the voltage not being reliable from the dial and that needs to be replaced? Anyone have luck with this ultimately being the control unit?