I have a Hobart KitchenAid Mixer Model K45SS and it runs fast on low (Surges speeds up and down)what is causing this problem

Try replacing the phase board, it's above the speed control plate with 4 wires coming out of it.

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

is it a K45 or a K45SS? If it is a K45 you will have to replace the filters inside and probably the speed control plate, if it is a K45SS then you need a new phase control board. The K45 is pre 1978 and the K45SS is post 1978. Your information is correct on pre 1978 K45 models that the capacitor is bad, but it might be cheaper to go garage sale hunting and find a second machine as the parts are no longer made and having spares on hand may be a significant advantage in the future, also there are a great many of the K45SS parts that will also repair the K45 mixer so it may not be a practical solution. Watch ebay regularly for K45 parts, they come up every couple of months. On the parts diagram also look for the K5 diagram as it is identical to the K45, one is a 5 quart mixer and the other one is 4.5 quart, same parts same motor same everything.

You can get the high speed back if you want to play with those three screws. there is a timing scheme for your mixer and it is set and adjusted by manipulating those 3 screws. The bottom center screw is for speeds 6 8 and 10. The best choice is to replace this switch, about $10 bucks on ebay.

What everyone is forgetting or they just don't know is that...The K45 introduced by Hobart in 1962 and was replaced in 1978 by the K45SS are two completely different machines. With completely different wiring systems. The K45 is wired together with wire nuts and the K45SS used connectors on the Speed control switch. All of the websites posted above are for the K45SS (Stands for Solid State) The manual for he K45SS is easy to get from Kitchenaid as the mixer electronics did not change from it's introduction in 1978 to 1986 when Hobart sold the Kitchenaid division to Whirlpool. The K45 on the other hand is a product and property of Hobart NOT Whirlpool or the Kitchenaid division of Whirlpool. The K45 Manual ... well I just can't find one! They way wires are routed is totally different in the K45 from the K45SS so the diagram in the K45SS manual does not help. Also the brushes in the K45 were square not camphor-ed like they are in the K45SS so there is no right or wrong way to insert the brushes in a K45. Whereas; in the K45SS there are four ways to insert the brushes in their holder and three of them are wrong. The K45SS brushes go into a completely different brush holder than the K45. The K45SS is the same today in 2012 as it was in 1978. The K45 is the same only from 1962 when Hobart introduced it to 1978 when it was replaced with the new Solid State model. prior to 1962 it was the K4-A model and it was different entirely. So if the people asking for help say their mixer is a K45 we should be asking for clarification as to a K45 or a K45SS.

Change the speed control board. Repair alot of these

Hi. Go to mendingshed.com and download their free Kitchenaid Service Manual. This valuable document will help you to tune up your mixer, and covers the K45SS model. They also sell kitchenaid parts.

Go to kitchenaid.com and search for a parts manual for your mixer. Enter your model# thusly k45sswh.

If this solution has assisted you, please rate it. Good luck! ricardok45.

Hi. Goto www.mendingshed.com , locate and download the free Kitchenaid Service Manual. This is a comprehensive manual and will help you with your task. You can also go to the Kitchenaid website and download the Parts Catalog for your mixer model.
Good luck!

If this solution has assisted you, please rate it. ricardok45.

Hiya,

Sorry to hear you are experiencing an issue with your appliance.
We have created some videos, that might help you resolve this issue. Please see one of the links below:

https://www.youtube.com/watch?v=bM3t46afGcc
https://www.kaparts.co.uk/Help/KitchenAidHelp/KitchenAidMixerHelp/KitchenAidSpeedSettings/tabid/615/Default.aspx