Fixin’ Stuff Because You Could

They just don’t make stuff anymore like they used to. Not that old stuff was perfect, or anything, but repair on older appliances and things like that usually aren’t too difficult at all, on the rare occasion they’re needed.

Case in point: last week, our (twenty-year-old) dehumidifier quit working. Some disassembly later, it turned out one of the main power wires had burned through. Why? Because the fan had seized. I stripped down the motor, cleaned out the hardened oil, re-lubricated it, re-assembled the fan, then soldered the burnt wire, and hey presto, it works again, good as new.

Repair was greatly simplified by the owner’s manual, which thoughtfully includes a wiring diagram.

On the other hand…

…consider our leaf blower. It’s the second one we’ve owned in five or six years; the last one pretty much vibrated itself to death and disintegrated.

The new one, which is about two years old, worked a year ago, last fall. Now it doesn’t.

Before taking it to a small-engine shop to be told it’s unrepairable, my roommate and I figured we’d see if the cause of the problem was sufficiently obvious that we could work it out.

We’re pretty sure the ignition module is burned out and needs replacing, actually. Why? Mostly a process of elimination, and the fact that the spark plug was shorted, apparently because of carbon buildup. Replace the spark plug, and… nope, still not working.

I’m pretty good with the hardware side of electronics, so I decided to troubleshoot that, just to rule out any easy fixes. Because this thing is a mostly-plastic modern piece of shit, it doesn’t include anything helpful like a wiring diagram.

Then again, it’s a leaf blower – basically a little single-stroke motor, with attached magneto. There’s not a lot of wiring to follow.

Follow along if you’re familiar with electronic circuits, OK? In the handle of the leaf blower is a momentary toggle switch, which is used to stop the blower. The operation of this switch should be fairly intuitive, right? It’s normally-closed, and carries one half of the electrical circuit between the magneto/ignition coil and the spark plug. Depressing it opens the circuit, prevents the spark plug from firing, and causes the engine to stop.

Right? Apparently… no.

The switch is in fact normally open, meaning you stop the engine by closing a circuit between… something, and something. (No wiring diagram, remember?) This seems like a bad idea to me, but maybe there’s a reason I don’t design small motorized objects sold at big box stores. Anyway… one of the wires from the switch disappears somewhere into the bowels of the leaf blower, presumably connecting to the ignition coil. The other…

The other wire – honest to God – goes to a spade connector that sits on a (non-conductive; we checked) plastic stud, and doesn’t connect to anything.

We spent about two hours trying to figure out how in the hell this worked, but to no avail. I’ve been pondering it on and off for a couple of days, and have nothing.

You stop the engine by “shorting” some part of the electrical system to nothing – a piece of metal wedged between three pieces of nonconductive plastic.

Is this right? I don’t know. How does this work? I don’t know. Do they offer any sort of diagram explaining how the whole thing is put together? Of course not.

We’re going to take it in to the shop tomorrow, and see if it can be fixed. While we’re there, we’re going to see if the boffins know how the hell the shutoff switch is supposed to work.

When this one dies, I think we’re going to hunt around for a twenty- or thirty-year-old leaf blower, as replacement. The less headache-inducing modern crap in my life, the better.

Published in: 'D' for 'Dumb', Geekiness, General | on September 30th, 2010| 1 Comment »

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  1. On 9/30/2010 at 10:49 pm Pat Said:

    You’re describing the time-honored way of stopping a small engine: Shorting the spark plug. One end connects (more or less) to the plug. The other goes to ground. The aim is to disrupt the spark enough to stall the engine. Presumably at the high voltages involved, shorting to a piece of metal wedged between three pieces of plastic is enough for this engine.

    I’ve seen more than one engine that had long since lost it’s “official” switch and had to be stopped by shorting it with a screwdriver. (If you were lucky and the spark plug connector was uninsulated. The alternative is worse—pulling the insulated wire, which, believe me, isn’t insulated enough.)

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