i have a simpson maxidry 1200s heavy duty?

This sounds like the same problem I had.
WHEN YOU HAVE A BROKEN BELT I THINK THE TENSION
SPRING RELEASES/COMES LOOSE NATURALLY,ITS DESIGNED TO HOOK ONTO THE MIDDLE OF THE SENSOR SWITCH AND WHEN THE BELT BREAKS YOU LOOSE THE TENSION ON THE BELT.THE WAY I FIXED MY MAXIDRY WAS.
UNDO THE REAR COVER.IF YOU HAVE ANY TROUBLE DOING THIS THERE IS A PLASTIC TYPE SPLIT PIN IN THE MIDDLE OF THE INSIDE OF THE REAR COVER.LOCATED INSIDE THE FRONT OF THE DRYER.
THIS IS WHAT LOCKS THE DRUM IN PLACE. I THINK YOU HAVE TO GRAB A PAIR OF PLIERS AND SQUEEZE AND PUSH AT THE SAME TIME TOWARDS THE REAR OF THE DRYER TO RELEASE THE DRUM.

ONCE THE DRUM IS UNCOUPLED FROM THE DRYER I WAS TOLD TO TAKE OUT THE DRUM REMEMBERING WHICH WAY IT FACES AND LAY THE DRUM ON (4) PHONE BOOKS AROUND THE DOOR SO THE DRYER IS
UPSIDE DOWN,IT'S EASIER TO WORK ON. THIS STOPS YOU FROM BREAKING THE GLASS ON THE DOOR.

TAKE OUT THE DRUM.

UPON OPENING THE REAR YOU WILL PROBABLY NOTICE THAT THE DRUM BELT IS OFF OR BROKEN,IF SO YOU WILL FIND THE DOUBLE ENDED SPRING LAYING THERE SOMEWHERE.
IT PROBABLY IS A BROKEN BELT WHICH IS EASY TO FIX.
QUOTE THE MODEL NUMBER AND TYPE OF DRYER AS ABOVE TAKE THE OLD BELT WITH YOU FOR COMPARISON.
REPLACING NEW BELT IS EASY WHEN YOU YOU KNOW HOW.I DIDN'T BUT DO NOW.
WHILE THE DRUM IS OUT LOOK FOR THE WEAR MARK AROUND THE MIDDLE OF THE DRUM.
PLACE THE BELT AROUND THE MARK AND PUT A (3) INCH PIECE OF STICKY TAPE OVER THE BELT AGAINST THE DRUM.(EVERY 6 INCHES) THIS KEEPS THE BELT IN
PLACE.

PUT THE DRUM BACK IN AND STAND THE DRYER UP SO YOU CAN PULL THE PLASTIC SPLIT/LOCK PIN FROM THE INSIDE WITH THE PLIERS TO LOCK THE DRUM IN PLACE.
LAY DRYER BACK DOWN ON THE (4) CORNERS OF THE PHONE BOOKS AND SQUEEZE/PUSH THE LAST (6) INCHES OF THE BELT THROUGH THE METAL PULLEY AND HOOK ONTO PULLEY WHEEL!!!

GRAB THE SPRING AND HOOK AROUND THE LITTLE HOLE NEAR THE PULLEY AND STRETCH OVER TO THE SWITCH AND HOOK AROUND THE MIDDLE OF THE SWITCH. THE SPRING IS DESIGNED TO HOOK AROUND THE SWITCH SO DON'T WORRY.IF THE BELT BREAKS THE SENSOR IN THE SWITCH SENSES THE LOSS OF TENSION ON THE DRUM AND THE DRYER WON'T WORK.

ONCE THE DRUM IS LOCKED IN PLACE AND THE SPRING HOOKED ON CORRECTLY TO THE SWITCH TURN THE DRUM BY HAND AND START TAKING THE STICKY TAPE BACK OFF.BELIEVE ME IT IS WORTH PUTTING THE STICKY TAPE ON.KEEPS BELT CENTRED.
REPLACE THE REAR COVER AND TEST.

denniskadams@optusnet.com.au
July 2008

The spring is part of the tensioning mechanism for the drum belt, it is attached one end to the (broken) belt cut off switch at the base of the dryer and to the pivoting arm for tensioning the belt drive.

Russ
November 2006