diff --git a/board/boards/dos.h b/board/boards/dos.h
index 1a0187971b..436ddfa982 100644
--- a/board/boards/dos.h
+++ b/board/boards/dos.h
@@ -152,10 +152,6 @@ void dos_init(void) {
   pwm_init(TIM4, 2);
   dos_set_ir_power(0U);
 
-  // Initialize fan and set to 0%
-  fan_init();
-  dos_set_fan_enabled(false);
-
   // Initialize harness
   harness_init();
 
diff --git a/board/boards/red_chiplet.h b/board/boards/red_chiplet.h
index 3eb09832da..05cbd6c341 100644
--- a/board/boards/red_chiplet.h
+++ b/board/boards/red_chiplet.h
@@ -35,14 +35,14 @@ void red_chiplet_enable_can_transceivers(bool enabled) {
   }
 }
 
-void red_chiplet_set_usb_load_switch(bool enabled) {
+void red_chiplet_set_fan_or_usb_load_switch(bool enabled) {
   set_gpio_output(GPIOD, 3, enabled);
 }
 
 void red_chiplet_init(void) {
   common_init_gpio();
 
-  //A8, A9 : OBD_SBU1_RELAY, OBD_SBU2_RELAY
+  // A8, A9: OBD_SBU1_RELAY, OBD_SBU2_RELAY
   set_gpio_output_type(GPIOA, 8, OUTPUT_TYPE_OPEN_DRAIN);
   set_gpio_pullup(GPIOA, 8, PULL_NONE);
   set_gpio_mode(GPIOA, 8, MODE_OUTPUT);
@@ -75,7 +75,7 @@ void red_chiplet_init(void) {
   set_gpio_mode(GPIOB, 0, MODE_ANALOG);
 
   // Turn on USB load switch.
-  red_chiplet_set_usb_load_switch(true);
+  red_chiplet_set_fan_or_usb_load_switch(true);
 
   // Initialize harness
   harness_init();
diff --git a/board/boards/tres.h b/board/boards/tres.h
index 17836e6777..f3fb04cdd9 100644
--- a/board/boards/tres.h
+++ b/board/boards/tres.h
@@ -20,6 +20,9 @@ void tres_init(void) {
   set_gpio_alternate(GPIOE, 13, GPIO_AF5_SPI4);
   set_gpio_alternate(GPIOE, 14, GPIO_AF5_SPI4);
   register_set_bits(&(GPIOE->OSPEEDR), GPIO_OSPEEDR_OSPEED11 | GPIO_OSPEEDR_OSPEED12 | GPIO_OSPEEDR_OSPEED13 | GPIO_OSPEEDR_OSPEED14);
+
+  // fan setup
+  set_gpio_alternate(GPIOC, 8, GPIO_AF2_TIM3);
 }
 
 const board board_tres = {
@@ -33,7 +36,7 @@ const board board_tres = {
   .has_spi = true,
   .has_canfd = true,
   .has_rtc_battery = true,
-  .fan_max_rpm = 0U,
+  .fan_max_rpm = 6500U,  // TODO: verify this, copied from dos
   .init = tres_init,
   .enable_can_transceiver = red_chiplet_enable_can_transceiver,
   .enable_can_transceivers = red_chiplet_enable_can_transceivers,
@@ -42,7 +45,7 @@ const board board_tres = {
   .set_can_mode = red_set_can_mode,
   .check_ignition = red_check_ignition,
   .read_current = unused_read_current,
-  .set_fan_enabled = unused_set_fan_enabled,
+  .set_fan_enabled = red_chiplet_set_fan_or_usb_load_switch,
   .set_ir_power = unused_set_ir_power,
   .set_phone_power = unused_set_phone_power,
   .set_siren = unused_set_siren
diff --git a/board/boards/uno.h b/board/boards/uno.h
index b2762b0668..c401fb2998 100644
--- a/board/boards/uno.h
+++ b/board/boards/uno.h
@@ -192,10 +192,6 @@ void uno_init(void) {
   pwm_init(TIM4, 2);
   uno_set_ir_power(0U);
 
-  // Initialize fan and set to 0%
-  fan_init();
-  uno_set_fan_enabled(false);
-
   // Initialize harness
   harness_init();
 
diff --git a/board/drivers/fan.h b/board/drivers/fan.h
index cb5fbabe63..d5e32ae5f9 100644
--- a/board/drivers/fan.h
+++ b/board/drivers/fan.h
@@ -27,7 +27,7 @@ void fan_tick(void){
     current_board->set_fan_enabled(fan_state.target_rpm > 0U);
 
     // Stall detection
-    if(fan_state.power > 0U) {
+    if (fan_state.power > 0U) {
       if (fan_rpm_fast == 0U) {
         fan_state.stall_counter = MIN(fan_state.stall_counter + 1U, 255U);
       } else {
diff --git a/board/main.c b/board/main.c
index 94d0c7f741..3fb67d201b 100644
--- a/board/main.c
+++ b/board/main.c
@@ -239,8 +239,9 @@ void tick_handler(void) {
           // Also disable IR when the heartbeat goes missing
           current_board->set_ir_power(0U);
 
+          // TODO: need a SPI equivalent
           // If enumerated but no heartbeat (phone up, boardd not running), turn the fan on to cool the device
-          if(usb_enumerated){
+          if (usb_enumerated) {
             fan_set_power(50U);
           } else {
             fan_set_power(0U);
@@ -341,7 +342,7 @@ int main(void) {
     uart_init(&uart_ring_gps, 115200);
   }
 
-  if(current_board->has_lin){
+  if (current_board->has_lin) {
     // enable LIN
     uart_init(&uart_ring_lin1, 10400);
     UART5->CR2 |= USART_CR2_LINEN;
@@ -349,6 +350,10 @@ int main(void) {
     USART3->CR2 |= USART_CR2_LINEN;
   }
 
+  if (current_board->fan_max_rpm > 0U) {
+    llfan_init();
+  }
+
   microsecond_timer_init();
 
   // init to SILENT and can silent
diff --git a/board/stm32fx/llfan.h b/board/stm32fx/llfan.h
index 403314153d..3e4b0fa3fd 100644
--- a/board/stm32fx/llfan.h
+++ b/board/stm32fx/llfan.h
@@ -1,23 +1,23 @@
 // TACH interrupt handler
 void EXTI2_IRQ_Handler(void) {
-    volatile unsigned int pr = EXTI->PR & (1U << 2);
-    if ((pr & (1U << 2)) != 0U) {
-        fan_state.tach_counter++;
-    }
-    EXTI->PR = (1U << 2);
+  volatile unsigned int pr = EXTI->PR & (1U << 2);
+  if ((pr & (1U << 2)) != 0U) {
+      fan_state.tach_counter++;
+  }
+  EXTI->PR = (1U << 2);
 }
 
-void fan_init(void){
-    // 5000RPM * 4 tach edges / 60 seconds
-    REGISTER_INTERRUPT(EXTI2_IRQn, EXTI2_IRQ_Handler, 700U, FAULT_INTERRUPT_RATE_TACH)
+void llfan_init(void) {
+  // 5000RPM * 4 tach edges / 60 seconds
+  REGISTER_INTERRUPT(EXTI2_IRQn, EXTI2_IRQ_Handler, 700U, FAULT_INTERRUPT_RATE_TACH)
 
-    // Init PWM speed control
-    pwm_init(TIM3, 3);
+  // Init PWM speed control
+  pwm_init(TIM3, 3);
 
-    // Init TACH interrupt
-    register_set(&(SYSCFG->EXTICR[0]), SYSCFG_EXTICR1_EXTI2_PD, 0xF00U);
-    register_set_bits(&(EXTI->IMR), (1U << 2));
-    register_set_bits(&(EXTI->RTSR), (1U << 2));
-    register_set_bits(&(EXTI->FTSR), (1U << 2));
-    NVIC_EnableIRQ(EXTI2_IRQn);
+  // Init TACH interrupt
+  register_set(&(SYSCFG->EXTICR[0]), SYSCFG_EXTICR1_EXTI2_PD, 0xF00U);
+  register_set_bits(&(EXTI->IMR), (1U << 2));
+  register_set_bits(&(EXTI->RTSR), (1U << 2));
+  register_set_bits(&(EXTI->FTSR), (1U << 2));
+  NVIC_EnableIRQ(EXTI2_IRQn);
 }
diff --git a/board/stm32h7/llfan.h b/board/stm32h7/llfan.h
index fc529dcbe2..dce622503a 100644
--- a/board/stm32h7/llfan.h
+++ b/board/stm32h7/llfan.h
@@ -1,2 +1,23 @@
-void EXTI2_IRQ_Handler(void) { }
-void fan_init(void){ }
+// TACH interrupt handler
+void EXTI2_IRQ_Handler(void) {
+  volatile unsigned int pr = EXTI->PR1 & (1U << 2);
+  if ((pr & (1U << 2)) != 0U) {
+    fan_state.tach_counter++;
+  }
+  EXTI->PR1 = (1U << 2);
+}
+
+void llfan_init(void) {
+  // 5000RPM * 4 tach edges / 60 seconds
+  REGISTER_INTERRUPT(EXTI2_IRQn, EXTI2_IRQ_Handler, 700U, FAULT_INTERRUPT_RATE_TACH)
+
+  // Init PWM speed control
+  pwm_init(TIM3, 3);
+
+  // Init TACH interrupt
+  register_set(&(SYSCFG->EXTICR[0]), SYSCFG_EXTICR1_EXTI2_PD, 0xF00U);
+  register_set_bits(&(EXTI->IMR1), (1U << 2));
+  register_set_bits(&(EXTI->RTSR1), (1U << 2));
+  register_set_bits(&(EXTI->FTSR1), (1U << 2));
+  NVIC_EnableIRQ(EXTI2_IRQn);
+}
diff --git a/board/stm32h7/peripherals.h b/board/stm32h7/peripherals.h
index 01e9ff7c73..f87acd4960 100644
--- a/board/stm32h7/peripherals.h
+++ b/board/stm32h7/peripherals.h
@@ -102,6 +102,7 @@ void peripherals_init(void) {
   RCC->APB2ENR |= RCC_APB2ENR_SPI4EN;  // SPI
   RCC->AHB1ENR |= RCC_AHB1ENR_DMA2EN;  // SPI DMA
   RCC->APB1LENR |= RCC_APB1LENR_TIM2EN;  // main counter
+  RCC->APB1LENR |= RCC_APB1LENR_TIM3EN;  // fan pwm
   RCC->APB1LENR |= RCC_APB1LENR_TIM6EN;  // interrupt timer
   RCC->APB1LENR |= RCC_APB1LENR_UART7EN;  // SOM uart
   RCC->APB2ENR |= RCC_APB2ENR_TIM8EN;  // clock source timer