HOW TO TEST A PHASE CONTROL BOARD ON KITCHENAID MIXER

Here's a link for a Service Manual which applies to your mixer. While the motor works as you have stated, you might wish to test the motor's stator, and if that is all right, test the armature. There is plenty of information on armature testing on line.

http://www.kitchenaidparts.eu/documents/pdf/service-manual/classic-svc-manual-new-email-version.pdf

The Service Manual for your mixer can be found at:

http://www.kitchenaidparts.eu/documents/pdf/service-manual/classic-svc-manual-new-email-version.pdf

Among the causes for the mixer not turning on are (in no particular order) --

The leaf-spring switch on the Control Plate is not making contact.
The Phase Board is defective.
Brushes need replacement.
Brush chamfered side not correctly oriented.
Bad armature or field coil.
Seized motor bearing.
Detached or broken Control Board spring.
Speed Control Link plastic end broken.

See:

http://www.electronicspoint.com/threads/kitchenaid-mixer-phase-control-board-problem.241021/


http://howtomendit.com/answers.php?id=94960

It is most likely the phase board which is the little PCB under the back cover at the top, it has 4 wires coming out of it that plug into the black speed control board.

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

It sounds like you need a new speed control phase board:
http://kitchenaidmixerspares.co.uk/SearchResults/tabid/37/Default.aspx?Search=phase

Hiya,

Sorry you are experiencing an issue with your appliance. It would appear you need to replace your phase board. Please see one of the links below to assist you. Please note the videos show how to replace 230V phase board. The steps are the same for 110V. Please make sure you have the correct part for your appliance.

https://www.youtube.com/watch?v=era-Dp5P8Xw
https://www.kaparts.co.uk/Help/KitchenAidHelp/KitchenAidMixerHelp/KitchenAidReplacingyourphaseboard230volt/tabid/613/Default.aspx

It could be the phase control, or it could be that the governor assembly or associated spring is missing or malfunctioning.

I just did this last week!
1 Unplug Mixer 2 Remove screw on TOP of mixer body, at back. 3 Remove rear cover and paper-gasket thing (its not the end of  the world if you end up tearing it a little). 4 the phase control (little circuit board w/wires) is at the top (you  should see it very easily) held on by one screw, remove it. 5 when the circuit board is unscrewed, disconnect all the wires  that are connected FROM THE CIRCUIT BOARD to the  black control plate (NOT all wires-there should be 4 left on  the control plate at this point).  you don't need to  remember where all the colors go as the control plate is  labeled->but looking at them and making sure you  understand the abbreviations would be beneficial  (BK=black, BL=Blue RW=Red&White W=white R=red etc.   6 install new phase control (screw), either buy new thermal  grease (used to keep the board cool->it transfers heat to  the mixer's housing) or try to salvage what you can from  the old one. 7 connect wires, paying attention to labels. 8 reinstall paper gasket, then cover, then screw to hold on back- cover.