2016 POTD Thread Archive

ok fine, i'll make one too...;-p..

but beware this will be a 5 minute plus
 
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One of those days. We had to mow the lawn, and then I was free to spend the rest of the day in the shop. The three older kids are at their mother's house for the weekend and my wife is going shopping with her sister and their sons. Freedom! Right?

Nope. Riding lawn mower won't start. Battery is charged (and has a solar battery maintainer permanently connected), I've cleaned all the contacts, and I can't get it to turn over. Not even a click. Battery voltage doesn't drop in the slightest when I turn the key, so where's the problem??

Forget it. I am NOT spending a free day fixing an old mower. I have a plug-in electric that I use to run around the perimeter and tight spots. I'll just use it to mow the whole thing today and get it done.

Nope. It tripped a breaker. 12 gauge cord, 13 amp motor, so that's not the problem. I'll have to dig in after all.

Fascinating that both are having electrical problems at the same time. I blame the ranting about electricians that is going on in the Bozos thread lately. Bad karma or something. :(
 
i played the dead battery game monday...dragged my battery to wally world..they were all out..drug it over to auto zone..they had a nice high amperage battery for mowers...starts great now
 
I previously removed the battery pan from this thing and made a newer, much larger one to hold a serious battery. I will be very surprised if that's the problem (especially since there is no voltage drop when I turn the key).
 
So... Who wants to help me troubleshoot this thing? :)

I've replaced all sorts of AC motors, up to 7 HP 480V 3 Phase, but I have no experience and minimal knowledge about DC motors. I know there's a bridge rectifier, a safety lockout switch, and a two pole brushed DC motor. (Are they all two pole?) There is a tiny crack in the surface of the bridge rectifier, right next to the mounting screw, and charring on the motor mount right beside/above the rectifier. Seems to me that the rectifier is fried.

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A new one is $9 on Amazon. I would be delighted if that's all that's wrong here. But how do I determine if that's all that's wrong here? It seems to me that it is unlikely that the charring could have come from heat/sparks thrown by the motor itself because it's too focused right there. If it had come from the windings/brushes/stator/commutator/whatever below it would probably be more spread by this height.

A few more photos for context:

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$9 is a great price for a repair part on a project like this. But I have no interest in paying that if there's something else wrong. I have a Greenlee TK-30AGFI multimeter, so with instructions I can theoretically do any tests it's capable of. Less accessible are my brothers' professional models, but AC motors are not their field so I'm asking here since there's such a great group with a wide range of knowledge and experience.

Thanks? :)

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I've had very good experience purchasing batteries at a web site called 'Battery Shark.' I've purchased motorcycle and ATV batteries that would cost me $70 — $100 locally for $25 — $35, shipped.
 
Looks like these rectifiers go out with some regularity. I think I'll add a better heat sink (I have several in my to-melt aluminum scrap bin) and some thermal paste to hopefully prevent this problem in the future. Seems like some actual air circulation would also be in order. The cover is clearly designed to seal "completely", yet there was an incredible amount of grass clippings (roughly 1/3 of which, by height, had turned to rich soil) all around the top of the deck and base of the motor. The seal isn't working anyway, so perhaps adding a filtered air vent would be a good idea.


When it was connected in the back yard it tripped the breaker. But in the garage it didn't, so I'm thinking that's when it actually blew. And that has me concerned about my garage wiring (which I've wanted to upgrade anyway; only one 20 amp circuit for 120V and one 30 amp circuit for 240V). No GFCI, and presumably a poor ground connection. I guess this was a good thing to happen after all. :)
 
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