diff --git a/usermods/PWM_fan/readme.md b/usermods/PWM_fan/readme.md
index 976d6b24..8cd04a91 100644
--- a/usermods/PWM_fan/readme.md
+++ b/usermods/PWM_fan/readme.md
@@ -30,7 +30,16 @@ _NOTE:_ You may also need to tweak Dallas Temperature usermod sampling frequency
 
 No special requirements.
 
+## Control PWM fan speed using JSON API
+
+You can use e.g. `{"PWM-fan":{"speed":30,"lock":true}}` to set fan speed to 30 percent of maximum speed (replace 30 with arbitrary value between 0 and 100) and lock the speed.
+If you include `speed` property you can set fan speed in percent (%) of maximum speed.
+If you include `lock` property you can lock (_true_) or unlock (_false_) fan speed.
+If the fan speed is unlocked it will revert to temperature controlled speed on next update cycle. Once fan speed is locked it will remain so until it is unlocked by next API call.
+
 ## Change Log
 
 2021-10
 * First public release
+2022-05
+* Added JSON API call to allow changing of speed
\ No newline at end of file
diff --git a/usermods/PWM_fan/usermod_PWM_fan.h b/usermods/PWM_fan/usermod_PWM_fan.h
index a8df1202..ba4e1726 100644
--- a/usermods/PWM_fan/usermod_PWM_fan.h
+++ b/usermods/PWM_fan/usermod_PWM_fan.h
@@ -38,6 +38,7 @@ class PWMFanUsermod : public Usermod {
     #ifdef ARDUINO_ARCH_ESP32
     uint8_t pwmChannel = 255;
     #endif
+    bool lockFan = false;
 
     #ifdef USERMOD_DALLASTEMPERATURE
     UsermodTemperature* tempUM;
@@ -60,6 +61,8 @@ class PWMFanUsermod : public Usermod {
     static const char _tachoUpdateSec[];
     static const char _minPWMValuePct[];
     static const char _IRQperRotation[];
+    static const char _speed[];
+    static const char _lock[];
 
     void initTacho(void) {
       if (tachoPin < 0 || !pinManager.allocatePin(tachoPin, false, PinOwner::UM_Unspecified)){
@@ -205,7 +208,7 @@ class PWMFanUsermod : public Usermod {
       if ((now - msLastTachoMeasurement) < (tachoUpdateSec * 1000)) return;
 
       updateTacho();
-      setFanPWMbasedOnTemperature();
+      if (!lockFan) setFanPWMbasedOnTemperature();
     }
 
     /*
@@ -233,9 +236,19 @@ class PWMFanUsermod : public Usermod {
      * readFromJsonState() can be used to receive data clients send to the /json/state part of the JSON API (state object).
      * Values in the state object may be modified by connected clients
      */
-    //void readFromJsonState(JsonObject& root) {
-    //  if (!initDone) return;  // prevent crash on boot applyPreset()
-    //}
+    void readFromJsonState(JsonObject& root) {
+      if (!initDone || !enabled) return;  // prevent crash on boot applyPreset()
+      JsonObject usermod = root[FPSTR(_name)];
+      if (!usermod.isNull()) {
+        if (!usermod[FPSTR(_speed)].isNull() && usermod[FPSTR(_speed)].is<int>()) {
+          int pwmValuePct = usermod[FPSTR(_speed)].as<int>();
+          updateFanSpeed((MAX(0,MIN(100,pwmValuePct)) * 255) / 100);
+        }
+        if (!usermod[FPSTR(_lock)].isNull() && usermod[FPSTR(_lock)].is<bool>()) {
+          lockFan = usermod[FPSTR(_lock)].as<bool>();
+        }
+      }
+    }
 
     /*
      * addToConfig() can be used to add custom persistent settings to the cfg.json file in the "um" (usermod) object.
@@ -337,3 +350,5 @@ const char PWMFanUsermod::_temperature[]    PROGMEM = "target-temp-C";
 const char PWMFanUsermod::_tachoUpdateSec[] PROGMEM = "tacho-update-s";
 const char PWMFanUsermod::_minPWMValuePct[] PROGMEM = "min-PWM-percent";
 const char PWMFanUsermod::_IRQperRotation[] PROGMEM = "IRQs-per-rotation";
+const char PWMFanUsermod::_speed[]          PROGMEM = "speed";
+const char PWMFanUsermod::_lock[]           PROGMEM = "lock";