diff --git a/firmware/heater_control.cpp b/firmware/heater_control.cpp
index 712f611..4e54aeb 100644
--- a/firmware/heater_control.cpp
+++ b/firmware/heater_control.cpp
@@ -32,17 +32,20 @@ static HeaterState GetNextState(HeaterState state, float sensorEsr)
                 rampDuty = 0.5f;
                 return HeaterState::WarmupRamp;
             }
-            else
-            {
-                // Stay in preheat - wait for time to elapse
-                return HeaterState::Preheat;
-            }
+
+            // Stay in preheat - wait for time to elapse
+            break;
         case HeaterState::WarmupRamp:
             if (sensorEsr < 2000)
             {
                 return HeaterState::ClosedLoop;
             }
+
+            break;
+        case HeaterState::ClosedLoop: break;
     }
+
+    return state;
 }
 
 static float GetDutyForState(HeaterState state, float heaterEsr)
@@ -61,17 +64,18 @@ static float GetDutyForState(HeaterState state, float heaterEsr)
         case HeaterState::ClosedLoop:
         {
             // do something more intelligent here
-            float error = (300 - heaterEsr) / 100;
+            float error = (heaterEsr - 250) / 100;
 
             return error * 1.0f;
         }
     }
 }
 
+static HeaterState state = HeaterState::Preheat;
+
 static THD_WORKING_AREA(waHeaterThread, 256);
 static void HeaterThread(void*)
 {
-    HeaterState state = HeaterState::Preheat;
 
     while (true)
     {
@@ -97,3 +101,8 @@ void StartHeaterControl()
 
     chThdCreateStatic(waHeaterThread, sizeof(waHeaterThread), NORMALPRIO + 1, HeaterThread, nullptr);
 }
+
+bool IsRunningClosedLoop()
+{
+    return state == HeaterState::ClosedLoop;
+}
diff --git a/firmware/heater_control.h b/firmware/heater_control.h
index 2bfdca7..5f94282 100644
--- a/firmware/heater_control.h
+++ b/firmware/heater_control.h
@@ -1,3 +1,4 @@
 #pragma once
 
 void StartHeaterControl();
+bool IsRunningClosedLoop();
diff --git a/firmware/pump_dac.cpp b/firmware/pump_dac.cpp
index 2875a10..8a820db 100644
--- a/firmware/pump_dac.cpp
+++ b/firmware/pump_dac.cpp
@@ -1,5 +1,6 @@
 #include "pump_dac.h"
 #include "pwm.h"
+#include "heater_control.h"
 
 #include "wideband_config.h"
 
@@ -19,10 +20,16 @@ void InitPumpDac()
 
 void SetPumpCurrentTarget(int32_t microampere)
 {
+    // Don't allow pump current when the sensor isn't hot
+    if (!IsRunningClosedLoop())
+    {
+        microampere = 0;
+    }
+
     // 47 ohm resistor
     // 0.147 gain
     // effective resistance of 317 ohms
-    float volts = 0.000321162f * microampere;
+    float volts = -0.000321162f * microampere;
 
     // offset by half vcc
     volts += HALF_VCC;
diff --git a/firmware/sampling.cpp b/firmware/sampling.cpp
index 68f92e9..91cd589 100644
--- a/firmware/sampling.cpp
+++ b/firmware/sampling.cpp
@@ -78,6 +78,6 @@ float GetPumpNominalCurrent()
     // Gain is 10x, then a 61.9 ohm resistor
     // Effective resistance with the gain is 619 ohms
     // 1000 is to convert to milliamperes
-    constexpr float ratio = 1000 / (PUMP_CURRENT_SENSE_GAIN * LSU_SENSE_R);
+    constexpr float ratio = -1000 / (PUMP_CURRENT_SENSE_GAIN * LSU_SENSE_R);
     return pumpCurrentSenseVoltage * ratio;
 }