diff --git a/arduino_32U4.h b/arduino_32U4.h
index 0634f4d..bde5b79 100644
--- a/arduino_32U4.h
+++ b/arduino_32U4.h
@@ -37,14 +37,18 @@
 #define SDA          DIO6
 
 // timers and PWM
+// The 32U4 PWMs are fairly restricted. If you avoid timer 1 for the clock, 
+// two pairs of the PWMs are complements of each other:
+// DIO11 & DIO12 on ~OC4D & OC4D and DIO14 & DIO15 on ~OC4B & OC4B
 #define TIMER4_IS_10_BIT
 #define OC0A         DIO4
 #define OC0B         DIO5
-#define OC3A         DIO9
+#define OC3A         DIO9  // 10 bit timer on OC4A, inverse of PWM on DIO10
 #define OC4A         D1O10
+//#define OC4B         DIO14  // inverse of PWM on DIO15
+#define OC4B         DIO15
+//#define OC4D         DIO11  // inverse of PWM on DIO12  
 #define OC4D         DIO12
-#define OC1A         DIO14
-#define OC1B         DIO16
 
 
 // change for your board
@@ -85,8 +89,6 @@ pins
 // Timer 1 would be a problem drf 2012-01-09
 // Timer 0 might be used by serial.c 
 #define DIO4_PWM     &OCR0A
-//#define DIO4_PWM     &OCR1C
-//#define DIO4_PWM     NULL
 #define DIO4_DDR     DDRB
 
 #define DIO5_PIN     PIND0
@@ -117,7 +119,7 @@ pins
 #define DIO9_PIN     PINC6
 #define DIO9_RPORT   PINC
 #define DIO9_WPORT   PORTC
-#define DIO9_PWM     &OCR3A
+#define DIO9_PWM     &OCR3AL  // inverse of DIO10_PWM
 #define DIO9_DDR     DDRC
 
 #define DIO10_PIN    PINC7
@@ -129,8 +131,7 @@ pins
 #define DIO11_PIN    PIND6
 #define DIO11_RPORT  PIND
 #define DIO11_WPORT  PORTD
-// note that this PWM is true on not-OCR4D
-#define DIO11_PWM    &OCR4D
+#define DIO11_PWM    NULL  // inverse of DIO12_PWM
 #define DIO11_DDR    DDRD
 
 #define DIO12_PIN    PIND7
@@ -148,7 +149,7 @@ pins
 #define DIO14_PIN    PINB5
 #define DIO14_RPORT  PINB
 #define DIO14_WPORT  PORTB
-#define DIO14_PWM    &OCR4B
+#define DIO14_PWM    NULL  // inverse of DIO15_PWM
 #define DIO14_DDR    DDRB
 
 #define DIO15_PIN    PINB6
diff --git a/heater.c b/heater.c
index d6c1282..b473a16 100644
--- a/heater.c
+++ b/heater.c
@@ -129,8 +129,12 @@ void heater_init() {
 	#ifdef	TCCR4A
 		#ifdef TIMER4_IS_10_BIT
 			// ATmega16/32U4 fourth timer is a 10 special bit timer
-			TCCR4D = MASK(WGM40);
-			TCCR4B = MASK(CS40);
+			TCCR4A = MASK(PWM4A) | MASK(PWM4B) ; // enable A and B
+			TCCR4C = MASK(PWM4D); // and D
+			TCCR4D = MASK(WGM40); // Phase correct
+			TCCR4B = MASK(CS40);  // no prescaler
+			TC4H   = 0;           // clear high bits
+			OCR4C  = 0xff;        // 8 bit max count at top before reset
 		#else
 			TCCR4A = MASK(WGM40);
 			TCCR4B = MASK(WGM42) | MASK(CS40);
@@ -138,6 +142,9 @@ void heater_init() {
 		TIMSK4 = 0;
 		OCR4A = 0;
 		OCR4B = 0;
+		#ifdef OCR4D  
+			OCR4D = 0;
+		#endif
 	#endif
 
 	#ifdef	TCCR5A
@@ -198,6 +205,11 @@ void heater_init() {
 					case (uint16_t) &OCR4B:
 						TCCR4A |= MASK(COM4B1);
 						break;
+					#ifdef OCR4D  
+						case (uint16_t) &OCR4D:
+							TCCR4C |= MASK(COM4D1);
+							break;
+					#endif
 					#endif
 				#endif
 				#ifdef	TCCR5A