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I have a fairly new kitchen aid artisan. Recently we probably did a larger batch of dough, than reasonable and there was some burnt smell. After that the kitchen aid won't turn on on the lower two speeds. It will only work on speed 3, which seems to me to be the new speed one, basically very slow. I know that kitchen aid has plastic gears which are designed as breaking points, so the motor doesn't break. But what could cause this effect? Is it most likely the famous plastic gear or could it be something else?

user1721135
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I realize this is an old question and the issue has probably been resolved since, but still, there is one other thing to debug.

This was probably not a broken worm gear. The symptoms of a broken worm gear are that the machine does not turn at all, or that it turns without load but stops as soon as any torque is applied.

The KitchenAid is basically fix geared. Speed is controlled not via gears, but via the motor. On the motor shaft is a "governor", a tiny contraption that moves outwards when the motor spins due the centrifugal forces (please no discussion if this is actually a force).

The speed control lever is connected via a shaft to a movable part, the speed control plate, that sits behind the governor. If the governor hits the speed control plate it pushes against a contact that interrupts the flow of electrical power to the motor. The motor powers down, the governor slides inwards until it releases the contact, power is restored, the governor moves outwards again and so on.

Via the speed control lever you can regulate the distance between the speed control plate and the governor. If the KitchenAid works in high gears but not in low gears, then the cause usually is that the spring loaded screws that hold the speed control plate in place do not provide the correct tension; this changes the distance between governor and speed control plate, and the breaker contacts might be triggered in the rest position stop the motor from running (that is why higher gears work - the third position of the speed lever now creates the same distance between governor and speed control plate as the first gear in a properly aligned machine).

This is quite easy to check. On the rear end of the machine, at the top, there is a single screw; if you remove that, you can remove the dome shaped cover at the end. This will give you access to the speed control plate. You will see that is affixed with two spring loaded screws; at the bottom of the speed control plate, you should see the shaft from the speed control lever latching into a notch in the speed control plate (used to be made from metal, these days it plastics and breaks sometimes). With a Philips head screwdriver you can adjust the screws to see if this makes any difference (you can also check for bent contacts on the speed control plate - these are essentially just bent copper strips that are pressed against each other to close a circuit).

You should probably unplug the machine first, since the contacts are unprotected.

Eike Pierstorff
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  • Thank you for this late reply, I have to admit the issue has not been solved, I simply use the machine on higher speeds since I wasn't sure what the issue is and what to change. I will try this. – user1721135 Aug 23 '23 at 11:54
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all non-pro Kitchenaid mixers have plastic gears, if used properly it should not be an issue.

According to this, the plastic gear is a "safeguard" :

"This gear is designed to shear or break apart should the machine bind up and protects the motor from burning up or otherwise become damaged. They are available for all models through Amazon or other vendors and easily replaced by anyone with a little mechanical aptitude."

You said that you made a larger batch, maybe it pushed the motor too hard and something had to break.

You should try to get it fixed.

Max
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The motor has likely overheated (not uncommon when overloaded and operating at low speed), melting some of the insulation in its coils and causing it to operate at lower torque. There's no fix for this other than replacing the motor. The good news is, replacement motors are reasonably priced and straightforward to install. (Only use genuine KitchenAid replacement parts.)

Sneftel
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    But why would low torque cause just the first two speeds not to work? And wouldn't overloading break the plastic gear, as designed before the motor breaks? – user1721135 May 15 '21 at 23:14
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    Kitchenaid mixers don't have variable gearing. When set at low speeds, they're working at lower voltage, in an inefficient region of their torque curve. The thing can't run at low speeds because it's no longer efficient enough to work at all at that power setting. The breakable gear is designed to prevent damage to the rest of the geartrain at high torque; it is not designed to protect the motor. – Sneftel May 16 '21 at 00:28
  • This makes perfect sense unfortunately. right now it runs on 3rd speed as it would on 1st speed. Is that consistent with what you are saying? Can I use this opportunity to put in a better / stronger motor? – user1721135 May 16 '21 at 09:21
  • I’m not aware of any aftermarket improvements like that, and I suspect that the stock motor is pretty much as good as it gets given the constraints. If you want more mixing power, you’ll need a more powerful mixer overall. A Kitchenaid stand mixer is a good all-round device for its price range, capable of tackling everything from dough to meringues, but that comes with some compromises. – Sneftel May 16 '21 at 09:49
  • I was thinking more along the lines of another kitchen aid motor, assuming it would fit. – user1721135 May 16 '21 at 18:47
  • It definitely won’t fit. – Sneftel May 16 '21 at 19:25
  • Could it also be the phase control? – user1721135 May 16 '21 at 20:59