From 2f14934c65efc139d242836fb5ad70493f3e83d7 Mon Sep 17 00:00:00 2001
From: Scott Lahteine <sourcetree@thinkyhead.com>
Date: Sun, 15 May 2016 18:54:37 -0700
Subject: [PATCH] Fix checkExtruderAutoFans

Make sure to only set the fan state once when extruders share a fan
---
 Marlin/temperature.cpp | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/Marlin/temperature.cpp b/Marlin/temperature.cpp
index 76bab525f9..5a03a18cb9 100644
--- a/Marlin/temperature.cpp
+++ b/Marlin/temperature.cpp
@@ -346,13 +346,15 @@ int Temperature::getHeaterPower(int heater) {
       if (current_temperature[f] > EXTRUDER_AUTO_FAN_TEMPERATURE)
         SBI(fanState, fanBit[f]);
     }
+    uint8_t fanDone = 0;
     for (int f = 0; f <= 3; f++) {
       int8_t pin = fanPin[f];
-      if (pin >= 0) {
-        unsigned char newFanSpeed = TEST(fanState, f) ? EXTRUDER_AUTO_FAN_SPEED : 0;
+      if (pin >= 0 && !TEST(fanDone, fanBit[f])) {
+        unsigned char newFanSpeed = TEST(fanState, fanBit[f]) ? EXTRUDER_AUTO_FAN_SPEED : 0;
         // this idiom allows both digital and PWM fan outputs (see M42 handling).
         digitalWrite(pin, newFanSpeed);
         analogWrite(pin, newFanSpeed);
+        SBI(fanDone, fanBit[f]);
       }
     }
   }