This project is meant to add a bit of comfort to old cars. The Tavria/Slavuta was a family of Ukrainian cars produced for a whopping 24 years - from 1987 up until 2011. It was beloved by many as a first or a cheap car, but lacks many comfort features. Its heating system doesn't have good adjustability, temperature is controlled by a mechanical valve with a Bowden cable and setting a comfortable temperature is a pain. Moreover, it depends on driving speed, so be ready to open windows on a highway.
I developed an electronic controller that acts as a drop-in replacement for the factory control mechanism. This controller measures the car interior temperature and maintains it by means of an electric valve, installed in place of the factory one. Also, it features a PWM fan speed control, replacing 3-step factory switch, which is too fast and loud even on the lowest speed.
The controller is built on a PIC16F684-I/SL MCU, few power mosfets (IRF4905PBF and IRF7831PbF), couple of potentiometers and a pinch of passive elements. It is not particularly DIY-friendly, as it uses SMD components, but the PCB is single-sided and can be made at home using a laser printer and a toner transfer process.
I've been using this system for a few years and all I can say: it is a noticeable improvement in comfort and control.
Project website (Ukrainian): slavuta-ccm.ho.ua