The mixer will not run @ very slow speed. When you try to adjust the speed, it jumps ahead to a much faster speed.

Check the carbon brushes under the black screw caps on the sides.

Usually when the mixer runs only on high speed it is caused by the control plate adjusted incorrectly or the control plate spring unhooked. Remove the trim & end cover on the mixer and check the control plate spring, if unhooked, attach to bottom of the control plate and squeeze the spring end, also check the speed control plate screws,there are 3 screws on this plate, one at the bottom two at the top, see if adjusting the top screws slows your mixer down.
Next check the wiring of the mixer, Insure everything is wired correctly, to get wiring diagram go to the last page of the service manual. Here is a link to the service manual: http://lib.store.yahoo.net/lib/mendingshed/kitchenaidservicemanual.pdf
If neither of those fixes the problem it is probably a bad phase control board, or a shorted phase control board. With the line cord disconnected, pull the t-bar contacts to open and insert a piece of paper between them so they cannot close. Reapply power-the mixer should just run or buzz trying to run, if it operates at full speed the phase control is defective and needs to be replaced.
Use the service manual to aid you in taking apart the mixer, trouble shooting the problem and putting the mixer back together, based on the mixer only running at high speed some of the time I would assume it is the speed control phase board.
If you have any questions let me know.
Thank you,
Colleen
Customer Service
MendingShed.com

If your mixer only runs on high speed there are 3 things that can cause that. The first thing to check will be the speed control plate, Remove the trim and end cover on the mixer, the first thing you should see is the speed control plate, this has 3 screws on it, try adjusting the top two screws 1/4 turn, this should slow the mixer down, do not over tighten. Also check to see if the control plate spring is unhooked. If the spring is unhooked, attach to bottom of the control plate, and squeeze the spring end.
If this does not fix your mixer, check the wiring of the mixer, you can locate a wiring diagram on the last page of the service manual.
If the speed control plate is adjusted correctly and all the wiring is correct it will be your speed control phase board. You can test the speed control phase board to see if it is shorted. With the line cord disconnected, pull the t-b ar contacts to open, and insert a piece of paper between them so they cannot close. Reapply power-the mixer should just run or buzz trying to run. If it operates at full speed, teh phase control board is defective and needs to be replaced.
Here is a link to the service manual: http://lib.store.yahoo.net/lib/mendingshed/kitchenaidservicemanual.pdf
This will aid you in taking the mixer apart, troubleshooting and putting it back together, remember the wiring diagram is the very last page.
Thank you,
Colleen
Customer Service
MendingShed.com
800-339-9297

remove rear coverdome, dust off mechanism carefully with a vacuum and small brush. Inspect all the parts- the black plate with the wires connecting to it is the speed control; beneath it are centrifugal weights which form the governor- the faster the motor spinsthe further the governor assy pushes out agatnst the contacts on the control plate to keep the speed smoothly moderated. If you have speed control but it just runs too slow or not slow enough the two screws at top of the control plate can adjust the speed; loosten the jam nut slightly and adjust the screws evenly together. Be sure theres nothing worn out or damaged which could be fatal to the mechanism later.

note tht the bottom of the control plate is retained by a wire hook on the end of a spring. It is a problem to catch and pull out if you lose it inside the mixer. If you set speed too low you will lose all power at low speeds.

The condensor at top of nontrol plate has only two wires from it out either side a flat cardboard tube. If shorted you will lose all speed adjustment. Test by disconnecting one or both wires.DO NOT RUN MIXER WITHOUR CONDENSOR except for brief testing... otherwise your trouble is the PC board- the white grease is important behind the heat sink dont remove it (standard heatsink grease for computers, etc.)
Best of luck!

Likely, you have an open resistor pack which may or may not be repairable located near the rear of the motor housing. Hope this helps!

It sounds like the speed control plate is not correctly adjusted. If you take the back cover off of the mixer (it is held in place with a screw at the top) and try adjusting the screws on the back plate you may be able to get the mixer to slow down.

You will notice two screws at the top of the speed control plate:
If you turn the top screws one quarter turn, both equally then test the mixer it should adjust the speed. Please make sure not to over tighten or loosen these screws as it can damage the speed control plate! You should not have to mess with any wires attached to the speed control plate or the bottom screw.

If you need more information please see the service manual here: http://ep.yimg.com/ty/cdn/mendingshed/kitchenaidservicemanual.pdf
It will specifically go over how to trouble shoot the mixer and how to adjust the speed control plate.

Please let me know if you have any questions

-Colleen @Mending Shed

You can try adjusting the speed control as shown in section 6 of the service manual:

http://lib.store.yahoo.net/lib/mendingshed/kitchenaidservicemanual.pdf

Also remove and clean the brushes as shown in the same manual pg 8 fig. #30.

Aussie helpline
1800-990-990

The speed control is a governor setup, it's purely on and off, as the weights on the motor shaft spin faster, they press against the contacts, and when they spin a fast enough speed, it turns off current to the motor, which makes it slow down, and current gets turned back on.  That way, you get a pretty consistent speed on a setting no matter whether it's lightly loaded or whipping something fairly heavy.  If you can turn the motor shaft by hand, then you don't have anything binding, but you might have gotten the speed control out of adjustment.  give it another go.

It's a problem with tachogenerator. You can buy this part pretty cheap and replacing is not that hard. (It's the gears under the blender/juice maker attachment) Basically while spinning it measures the speed and sends it back to motherboard to calculate how to adjust speed so it matches the setting. Replacing should help if it's broken. Although might be worth a try too just clean it. If some dirt or liquid got inside I might disturb the mechanism and cause problems. In my case just cleaning fixed the situation drastically.