The Short Version: I had improperly routed a new belt, which damaged the brake safety switch. Re-routing the belt and replacing the switch will fix this problem. A new switch is relatively inexpensive. Photos and links are included in this post.
A few weeks ago I (incorrectly) replaced the drive belt on our Craftsman lawn tractor. My mistake, which I didn’t learn immediately, was to improperly route the belt through the front part of the mower. Instead of going to the right of the brake assembly I went to the left. This caused the belt to wear against part of the brake system. Unknown at the time, not only did this ruin the new belt but it also damaged the brake safety switch.
While attempting to mow the back yard my wife stopped the mower at one point and from then on we were unable to get it to start again. It wouldn’t even attempt to crank (turn over). There was no click when moving the key. Nothing.
I tested the battery but showed that it had a good charge. Over the course of a week I started to look the mower over and ended up getting an education on just how the mower works and how the three main safeties interact. After several days I began to suspect the brake safety switch since it was the first switch in line and would prevent the mower from even cranking if it was damaged.
Had it been a bad seat switch, as I initially thought, the mower would have attempted to start but died (depending on some additional conditions).
The following weekend, when I finally had more time to investigate this problem further, I located the brake safety switch. On this model it is located on the left side of the mower, adjacent to the brake pedal. The following photo shows the general location of the switch:
A tactile inspection by hand of the button (located on the side of the switch facing down to the ground) quickly revealed that the switch was damaged. The following photo better illustrates the location of the switch though at this point I had already removed it so all you can see is the gap in the metal chassis where it had been installed (the wire harness off to the side of the hole was plugged into the switch):
Here’s a close-up of the removed switch. You can clearly see where the belt ground a groove directly into the switch, preventing it from working:
In the above photo the damaged part should be a whole button that protrudes out and is pressed down by the brake assembly when the brake pedal is pushed in.
The replacement switch was inexpensive. Prices typically range from about $10-$13. I had planned to order directly from Sears Parts Direct but I decided to purchase the switch from Amazon.com instead.
I do not advocate permanently disabling any of the safety switches. However, I did manage to have a work-around that allowed us to mow the yard until the new part arrives. This was simply to pull the switch around so I could hold in the button by hand long enough to start the mower.
Since the safety switch cannot work as design it’s important to be very, very careful when starting the mower if using this temporary work-around. Specifically, you should still depress the brake and make sure that the mower is in neutral. Otherwise, you may find yourself lurching forward suddenly, and that can be a dangerous situation without both hands on the wheel.