diff --git a/CHANGELOG_LATEST.md b/CHANGELOG_LATEST.md
index aad562ed1..f09f8c363 100644
--- a/CHANGELOG_LATEST.md
+++ b/CHANGELOG_LATEST.md
@@ -16,6 +16,7 @@
 - Added in MQTT nested mode, for thermostat and mixer, like we had back in v2
 - Cascade MC400 (product-id 210) (3.0.0b6)
 - values for wwMaxPower, wwFlowtempOffset
+- RC300 `thermostat temp -1` to clear temporary setpoint in auto mode
 
 ### Fixed
 - telegrams matched to masterthermostat 0x18
diff --git a/src/devices/thermostat.cpp b/src/devices/thermostat.cpp
index 456307f8c..16c10b5bc 100644
--- a/src/devices/thermostat.cpp
+++ b/src/devices/thermostat.cpp
@@ -1731,6 +1731,10 @@ bool Thermostat::set_temperature(const float temperature, const uint8_t mode, co
                 offset = 0x0A; // manual offset
             } else {
                 offset = 0x08; // auto offset
+                // special case to reactivate auto temperature, see #737, #746
+                if (temperature == -1) {
+                    factor = 0xFF; // use factor as value
+                }
             }
             validate_typeid = monitor_typeids[hc->hc_num() - 1]; // get setpoint roomtemp back
             break;
@@ -1887,7 +1891,11 @@ bool Thermostat::set_temperature(const float temperature, const uint8_t mode, co
 
         // add the write command to the Tx queue. value is *2
         // post validate is the corresponding monitor or set type IDs as they can differ per model
-        write_command(set_typeid, offset, (uint8_t)((float)temperature * (float)factor), validate_typeid);
+        if (factor == 0xFF) {
+            write_command(set_typeid, offset, factor, validate_typeid);
+        } else {
+            write_command(set_typeid, offset, (uint8_t)((float)temperature * (float)factor), validate_typeid);
+        }
         return true;
     }