Fails to run

Check if the power going into the motor.
I would also check the motor coil and it brushes.

You really need to get a Multi meter and follow the power, you have replaced the phase board so we can probably discount it being that.
First check that the switch contacts behind the black control board are really touching when you move the speed control lever to turn the mixer on.
Next the cable, do you have continuity from the wall plug to the control board on phase & neutral, (Check green earth wire as well for the sake of safety) that will be the black wire and the white wire on the 2 lower plug in contacts on the black control board at the back.
Next remove the carbon brushes, do they have reasonable length and most importantly are they fitted correctly with the corner key aligned with the blocker at the bottom of the brush holder.
Next with brushes out check for field winding continuity. On the other side of that black control board to where the power comes in there will be a red wire and a white wire that disappear into the motor housing. One of the wires will have a circuit to one of the brass brush holders and the other wire will have a circuit to the other brush holder. The resistance of both of those circuits should be pretty much identical.
After you have done those tests you should begin to have a clue as to where the problem lies.

Remove the brush caps on the sides of the motor housing and check the carbon brushes. If they are worn out replace them. They are keyed and will only fit properly one way so be observant. If that's not the problem remove the back cover and check for broken wires on the black control plate. Make sure the switch on the bottom inside of the control plate is making contact. If still faulty check the cable for continuity to the control plate, cable connects to the black wire and the white wire on lower left of control plate. After that you need to check for continuity of the field coil windings. Only thing left after that would be the phase board pcb just above black speed control plate at the back.

Check carbon brushes under the black caps on the motor sides. They only go in ONE way so take care, there is a blocker in the square hole on one corner. Line it up with the missing brush corner. If it's not the brushes remove the back cover & check for broken wires. Do your checking with power unplugged.

If you took your brushes out to check them then your mixer will not work if you put the brushes back in the wrong way even if you fixed the original problem. the beveled side of the brushes must go back into the brush holders a very specific way/direction because the brush holders have a pinched corner on one edge that allows the brush to slide past and to make contact with the armature. if you are sure that the brushes are in the correct way lets proceed. (If not get a flashlight and look inside the brush holder for the pinched down corner and reinsert the brushes the right way)
fist the basics, I know it seems dumb to even think this but ... well you know.
1. check the outlet you are using for the mixer to see that it has power.
2. The outlet is hot, look at the rar top of the mixer you will see a small "Phillips Head" screw. take it out. and lift up and out at the same time to remove the the rear motor head cover.
3. take a moment and look at what you see. now look at the cord that you use to plug the mixer into the outlet. follow it back into the mixer head and you will see three wires. Green = ground and it is attached to the mixer frame with a #3 Phillips screw, leave it alone. the other two wires, one black and one white attach to what is called the speed control board by means of two flag style connectors. Are they attached? Or have they or either one of them come off?
4. if they are attached to the flag terminals, then get a multi meter and check for power between the terminals. the black test probe goes to the black lead on the mixer terminal, your red test lead goes on the white flag terminal attached to the mixer. personally i would disconnect these two leads before I tested them to avoid any safety issues with the mixer. If ther is no power to the terminals when you p,lug the cord into the wall then the cord is bad. Order one and replace it. you could also test the cord another way by checking for ohms resistance and you won't have to plug the cord in at all. Ohms testing is safer.
5, if the cord is good then the next thing to look at is the phase control board. that is a small computer style board above and behind the big black and copper board with 3 screws in it. It has 4 wires coming out of it. You probably have no real way to test this unless you are familiar with electrical :Bread Board" circuitry. i usually just carry a new one with me and replace it. It's faster.
6. If the system still does not start I remove speed control plate/board,The black and copper one. (there is a spring attached that will have to be removed, if you let it snap back into the machine you will have to dismantle the entire motor head to dig it out, so hook a cloth under it's clip that will hold it and keep it from snapping back into the mixer). Now install a new spped plate and test again. if you still have no power there are only two electric problems left one is the armature and the stator which are the two components that make up the motor, but it will require a complete tear down to replace. I have never had a motor go out. the problem is usually the cord or brushes. Let me know if this helped. If not we can post a location to the service manual and parts list for your mixer.

Hello Aliceoye,

I understand that you are haveing a problem with you Kitchen Aid Mixer. The reason your mixer is not comming on at all is either the brushed or the speed switch.

First lets check the brushed. On both sides of there are little plastic holders with a slot in them. Remove one at a time, if there is still a black material at the end of the spring then that one is good. Now look up inside the hole and see the little notch stick down make sure that you put the tappered side up toward that and screw the cap back on. Do the same thing to the other side. Now check and see if the unit runs. If it stell does not run lets go the the next possibility.

Now we are going to check the speed switch.
1. Remove the back cover.
2. Take a electrical meter and check the power coming in to the unit the white and black wire, got voltage, unit still not working, unplug and lets proceed.
3. Move the speed switch backwards and forwards and see if the the shaft is moving the plate at the back of the unit that the wires are attached to. Yes, then your speed switch is bad.
4. Put everything back together and order this part PS1957234 the part cost $20.48 and can be purchased from partselect and the following link http://www.partselect.com/PartDetail.aspx?Inventory=1957234&imgID=1&Page=1&SourceCode=UNDEFINED

Thank you for choosing FixYa and we look forward to answer anymore questions you may have. If you have anymore questions please post them to this thread.

Check the carbon brushes, look inside the hole, it is keyed, the brushes only go in properly one way. Match the missing corner on the brush to the blocker inside the brush holder.

Hi, KIMAMABELL, While working on your mixer be sure to have the Parts List manual on hand. If you're lacking one, you can download a PDF version from the KA website at: http://www.kitchenaid.com/flash.cmd?/#/page/home.
Click on Customer Care>Locate Manuals & Guides> Enter the 6 character model number, in your case, KSM90P, and select one of the files listed under Parts List (check to see it this matches your mixer model).
Turn to pages 6 & 7, titled “Motor And Control Parts”, which provides an exploded view for the disassembly and reassembly of your mixer’s electrical components, along with all the parts. Locate Illus No 32, Brush holder that includes #18, 20, 21, 22, 23, and 31 which is the brush holder and brush & Spring assembly respectively.
The brushes need to be installed so that they both seat correctly on the armature's commutator and it’s possible when you reinstalled them, one or both brushes were turned incorrectly.
The illustration below shows the correct orientation of the brushes and should allow you to reinstall them with confidence.



Here are some links to several excellent websites that detail the disassembling/reassembly of a KA Mixer for your future referennce.

• http://www.artisanbreadbaking.com/discussions/kitchen-aid.htm
• http://www.neilcrockett.com/mixer.htm
• http://www.foodonthefood.com/food_on_the_food/2009/04/how-to-repair-a-kitchenaid-mixer-yourself.html

Between these three websites and their excellent pictures and descriptions and your Parts List manual, you should now be able to completely disassemble and reassemble your mixer.
Good luck! I hope this helps. Howard, Burke, VA
If this solution has been helpful to you, please rate it, thanks! - hslincoln

Remove the rear cap from the unit. Power comes in from the black wire with the white being common. Hold a voltmeter lead on the white and check for power on the black. Power goes across the bottom of the speed control unit via a buss bar. Check for power on the right side, I think it is a red wire (may be a white one). Power is taken into the motor via that wire, goes thru the windings and the brushes and then out the other brush wire and back to the board. Check for power on the return wire. If it is dead then either the windings in the motor are burned out or one of the brushes is dirty and needs to be cleaned and reseated prpperly [note there is one and only one way the brush goes in!!!! Install it incorrectly and the brush will not touch the commutator.

Try that and see if it runs after cleaning the brushes.

I had this problem also: power to the motor, motor not running.

Solution was simple: remove the 2 stators things from the sides of the main housing, clean all the black dust off them, re-insert and everything works fine.

The dust problem is similar to model train sets that I had as a kid at Christmas, the black dust acts as an insulator, preventing power from travelling between two metal parts that you'd think otherwise would conduct.