Embedded Systems · Deep Dive

Diesel Heater Controller

Reverse-engineering a 12V diesel heater's wireless remote and rebuilding its control system from scratch — three iterations from a hot-glued servo rig to a clean ESP32 + RF design with a phone Web UI.

Build Timeline

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Placeholder images — filter by iteration. Real photos coming soon.

3D Models

Parts I modeled for this build.

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Diesel Heater RF Remote — full assembly

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ESP-32 Custom Holder

Code Progression

How the firmware evolved across the three iterations. (Representative snippets — full source coming soon.)

// V1 — Arduino + hobby servos physically pressing the stock remote buttons.
#include <Servo.h>

Servo powerBtn;
Servo tempUp;

void setup() {
  powerBtn.attach(9);
  tempUp.attach(10);
}

void pressPower() {
  powerBtn.write(60);   // push
  delay(400);
  powerBtn.write(0);    // release
}

void loop() {
  // No automation yet — manual trigger only.
  // Problem: servos drift, hot glue mounts fail with vibration.
}

// V2 — Relays soldered to the remote PCB, emulating button presses electrically.
const int PIN_POWER = 4;
const int PIN_TEMP_UP = 5;

void setup() {
  pinMode(PIN_POWER, OUTPUT);
  pinMode(PIN_TEMP_UP, OUTPUT);
  digitalWrite(PIN_POWER, HIGH);   // relays active-low
  digitalWrite(PIN_TEMP_UP, HIGH);
}

void tapButton(int pin) {
  digitalWrite(pin, LOW);   // close contact
  delay(250);
  digitalWrite(pin, HIGH);  // open contact
}

// More reliable than servos, but relay contacts chatter
// and the extra wiring into the remote was fragile.

// V3 — ESP32 transmits the decoded 433MHz RF codes directly. No remote needed.
#include <RCSwitch.h>
#include <WebServer.h>

RCSwitch tx = RCSwitch();
WebServer server(80);

const unsigned long CODE_POWER  = 0xA1B2C3;  // sniffed from stock remote
const unsigned long CODE_TEMP_UP = 0xA1B2C4;

void sendCode(unsigned long code) {
  tx.send(code, 24);
}

void setup() {
  tx.enableTransmit(17);
  server.on("/power", []() { sendCode(CODE_POWER); server.send(200, "text/plain", "ok"); });
  server.on("/warmer", []() { sendCode(CODE_TEMP_UP); server.send(200, "text/plain", "ok"); });
  server.begin();
}

void loop() {
  server.handleClient();
  // + thermostat loop: read temp, hold setpoint automatically.
}

How It Works

The stock remote communicated with the heater over a one-way 433MHz link. Using an RF receiver module and a logic analyzer, I captured and decoded the button packets, then replayed them from an ESP32 — removing the physical remote from the loop entirely.

The ESP32 hosts a small Web UI on the van's local network, so the heater can be controlled from a phone: power, setpoint temperature, and a simple thermostat loop that holds the cabin temperature overnight. More detail, schematics, and the full source will be added here.