In Electric lawnmower repaired yet again I reported
After I reassembled the motor I tested the mower without replacing the cover—it seemed to work ok. I replaced the cover, and lawn mower worked just fine. I was too tired to mow the lawn (very little sleep last night, and the trip back from Berkeley had taken 6 hours, rather than 3 hours, because of BART delays, the BART train we were on going out of service, and missed connections), but I should be able to mow the lawn sometime in the next week.
I did mow the lawn the next week, but about halfway through I started having trouble with the mower. The motor ran fine, but if I squeezed the handle all the way it turned off again, making the mower rather difficult to control. I finished mowing the lawn, but decided to investigate the problem. At first, I thought that there might be a mechanical problem, with the handle releasing the switch when pulled too far, but I saw no evidence of that when I disassembled the handle and looked at the action of the cam on the handle.
Using my multimeter, I determined that the switch operated normally when the button was pressed part way, but not when the button was pressed in all the way. I suspected that this meant that the switch was damaged (perhaps by corrosion), so I ordered a new switch. Unfortunately, the part is quite expensive (about $15 on eBay), because it is a custom-made switch for Black and Decker.
I ordered the switch, and ebay said it had been shipped. I thought that the Post Office had reported it delivered, but I never saw it. I even asked the mailman about it two days after the claimed delivery, but he could not remember. He thought he had stuffed a thick envelope in the mail slot, but wasn’t sure. So either the post office did not deliver, or porch pirates had taken the package. [See update below.] Both outcomes seem to be likely here, based on reports on Nextdoor.
I ordered another switch which was shipped on 4/20 and arrived on 4/22. Today, I installed the switch.
The old switch, showing how the wires were connected. I took this picture before disconnecting any wires, in case I needed a reference for where they went.
The new switch, showing the part number. I transferred one wire at a time from the old switch to the new, so I didn’t need the reference photo that I took.
The new switch in place in the handle.
I disassembled the old switch to see if the contact damage was visible. The problem was not corrosion but burned material on the contacts—probably from the short circuits from the earlier rectifier failures.
I’ll try out the mower again this afternoon, to see whether this latest fix does the job. So far I have bought two bridge rectifiers, one set of brushes, and two switches to lengthen the life of this mower. At some point (perhaps at the next failure) it may be worth getting a new mower.
Update (still 2021 April 24): I mowed the lawn with the repaired lawnmower, and it worked fine. While I was mowing, the mailman came, with the package that had the first switch I had ordered. I went back to the USPS site to find out what had happened. It turned out that the ebay package that had been delivered was one for my wife, not the lawnmower switch. The switch had not arrived at the post office for ten days after the company (Parts Sales) had said they had shipped it. So the missing switch was neither the post office’s fault nor was it porch pirates—it was due to lies by the company claiming they had shipped when they hadn’t and confusion on my part about what package had been reported as delivered.