diff --git a/Marlin/src/module/temperature.cpp b/Marlin/src/module/temperature.cpp
index 11c3c58b7a..2481ab76bf 100644
--- a/Marlin/src/module/temperature.cpp
+++ b/Marlin/src/module/temperature.cpp
@@ -83,7 +83,9 @@
   #endif
 #endif
 
-#define MAX6675_SEPARATE_SPI (EITHER(HEATER_0_USES_MAX6675, HEATER_1_USES_MAX6675) && PINS_EXIST(MAX6675_SCK, MAX6675_DO))
+#if EITHER(HEATER_0_USES_MAX6675, HEATER_1_USES_MAX6675) && PINS_EXIST(MAX6675_SCK, MAX6675_DO)
+  #define MAX6675_SEPARATE_SPI 1
+#endif
 
 #if MAX6675_SEPARATE_SPI
   #include "../libs/private_spi.h"
@@ -2226,16 +2228,12 @@ void Temperature::disable_all_heaters() {
     #define THERMOCOUPLE_MAX_ERRORS 15
   #endif
 
-  int Temperature::read_max6675(
-    #if COUNT_6675 > 1
-      const uint8_t hindex
-    #endif
-  ) {
-    #if COUNT_6675 == 1
-      constexpr uint8_t hindex = 0;
-    #else
+  int Temperature::read_max6675(TERN_(HAS_MULTI_6675, const uint8_t hindex/*=0*/)) {
+    #if HAS_MULTI_6675
       // Needed to return the correct temp when this is called too soon
       static uint16_t max6675_temp_previous[COUNT_6675] = { 0 };
+    #else
+      constexpr uint8_t hindex = 0;
     #endif
 
     static uint8_t max6675_errors[COUNT_6675] = { 0 };
@@ -2263,26 +2261,19 @@ void Temperature::disable_all_heaters() {
     static millis_t next_max6675_ms[COUNT_6675] = { 0 };
     millis_t ms = millis();
     if (PENDING(ms, next_max6675_ms[hindex]))
-      return int(
-        #if COUNT_6675 == 1
-          max6675_temp
-        #else
-          max6675_temp_previous[hindex] // Need to return the correct previous value
-        #endif
-      );
+      return int(TERN(HAS_MULTI_6675, max6675_temp_previous[hindex], max6675_temp));
 
     next_max6675_ms[hindex] = ms + MAX6675_HEAT_INTERVAL;
 
-    #if COUNT_6675 == 1 && MAX6675_IS_MAX31865
-      max6675_temp = int(max31865_0.temperature(MAX31865_SENSOR_OHMS_0, MAX31865_CALIBRATION_OHMS_0));
-    #endif
-
-    #if COUNT_6675 > 1 && MAX6675_IS_MAX31865
-      #if hindex == 0
-        max6675_temp = int(max31865_0.temperature(MAX31865_SENSOR_OHMS_0, MAX31865_CALIBRATION_OHMS_0));
-      #elif hindex == 1
-        max6675_temp = int(max31865_1.temperature(MAX31865_SENSOR_OHMS_1, MAX31865_CALIBRATION_OHMS_1));
-      #endif
+    #if MAX6675_IS_MAX31865
+      max6675_temp = int(
+        #if HAS_MULTI_6675
+          hindex ? max31865_1.temperature(MAX31865_SENSOR_OHMS_1, MAX31865_CALIBRATION_OHMS_1)
+                 : max31865_0.temperature(MAX31865_SENSOR_OHMS_0, MAX31865_CALIBRATION_OHMS_0)
+        #else
+          max31865_0.temperature(MAX31865_SENSOR_OHMS_0, MAX31865_CALIBRATION_OHMS_0)
+        #endif
+      );
     #endif
 
     //
@@ -2293,7 +2284,7 @@ void Temperature::disable_all_heaters() {
       spiInit(MAX6675_SPEED_BITS);
     #endif
 
-    #if COUNT_6675 > 1
+    #if HAS_MULTI_6675
       #define WRITE_MAX6675(V) do{ switch (hindex) { case 1: WRITE(MAX6675_SS2_PIN, V); break; default: WRITE(MAX6675_SS_PIN, V); } }while(0)
       #define SET_OUTPUT_MAX6675() do{ switch (hindex) { case 1: SET_OUTPUT(MAX6675_SS2_PIN); break; default: SET_OUTPUT(MAX6675_SS_PIN); } }while(0)
     #elif HEATER_1_USES_MAX6675
@@ -2312,28 +2303,13 @@ void Temperature::disable_all_heaters() {
     // Read a big-endian temperature value
     max6675_temp = 0;
     for (uint8_t i = sizeof(max6675_temp); i--;) {
-      max6675_temp |= (
-        #if MAX6675_SEPARATE_SPI
-          max6675_spi.receive()
-        #else
-          spiRec()
-        #endif
-      );
+      max6675_temp |= TERN(MAX6675_SEPARATE_SPI, max6675_spi.receive(), spiRec());
       if (i > 0) max6675_temp <<= 8; // shift left if not the last byte
     }
 
     WRITE_MAX6675(HIGH); // disable TT_MAX6675
 
-    uint8_t fault = 1;
-    #if COUNT_6675 == 1 && MAX6675_IS_MAX31865
-        fault = max31865_0.readFault();
-    #elif MAX6675_IS_MAX31865
-      #if hindex == 0
-        fault = max31865_0.readFault();
-      #elif hindex == 1
-        fault = max31865_1.readFault();
-      #endif
-    #endif
+    const uint8_t fault = TERN0(MAX6675_IS_MAX31865, TERN_(HAS_MULTI_6675, hindex ? max31865_1.readFault() :) max31865_0.readFault());
 
     if (DISABLED(IGNORE_THERMOCOUPLE_ERRORS) && (max6675_temp & MAX6675_ERROR_MASK) && fault) {
       max6675_errors[hindex] += 1;
@@ -2364,15 +2340,7 @@ void Temperature::disable_all_heaters() {
             else if  (fault & MAX31865_FAULT_OVUV)
               SERIAL_ECHOLNPGM("Under/Over voltage");
 
-            #if COUNT_6675 == 1
-              max31865_0.clearFault();
-            #else
-              #if hindex == 0
-                max31865_0.clearFault();
-              #elif hindex == 1
-                max31865_1.clearFault();
-              #endif
-            #endif
+            TERN_(HAS_MULTI_6675, hindex ? max31865_1.clearFault() :) max31865_0.clearFault();
           }
         #else
           SERIAL_ECHOLNPGM("MAX6675");
@@ -2380,7 +2348,7 @@ void Temperature::disable_all_heaters() {
 
         // Thermocouple open
         max6675_temp = 4 * (
-          #if COUNT_6675 > 1
+          #if HAS_MULTI_6675
             hindex ? HEATER_1_MAX6675_TMAX : HEATER_0_MAX6675_TMAX
           #else
             TERN(HEATER_1_USES_MAX6675, HEATER_1_MAX6675_TMAX, HEATER_0_MAX6675_TMAX)
@@ -2399,9 +2367,7 @@ void Temperature::disable_all_heaters() {
       if (max6675_temp & 0x00002000) max6675_temp |= 0xFFFFC000; // Support negative temperature
     #endif
 
-    #if COUNT_6675 > 1
-      max6675_temp_previous[hindex] = max6675_temp;
-    #endif
+    TERN_(HAS_MULTI_6675, max6675_temp_previous[hindex] = max6675_temp);
 
     return int(max6675_temp);
   }