Router revving up and down - what could be causing this?

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Forum topic by EWJSMITH posted 03-10-2013 01:14 AM 1882 views 0 times favorited 12 replies Add to Favorites Watch
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156 posts in 3794 days

03-10-2013 01:14 AM

My King 3hp router doesn’t hold constant speed any more. Fired it up today in the router table and it was revving high, then low, then high again. I changed out the motor brushes with new ones but that didn’t change anything. Any suggestions as to what might be causing this? I’ve had this router for about 4-5 years now and never had a problem until today.

Any suggestions would be greatly appreciated.


12 replies so far

View Grandpa's profile


3259 posts in 2643 days

#1 posted 03-10-2013 03:26 AM

fluctuating power? Bearing that are trying to lock up? A bad connection. I assume the brushes are free to travel in and out. Armature that has a commutator that us badly out of round. Needs a good tossing? LOL

View MonteCristo's profile


2099 posts in 2156 days

#2 posted 03-10-2013 04:06 AM

My guess is it’s no longer serviceable. King isn’t a brand that I associate with quality/longevity.

-- Dwight - "Free legal advice available - contact Dewey, Cheetam & Howe""

View runswithscissors's profile


2725 posts in 1993 days

#3 posted 03-10-2013 05:16 AM

You can sell it on CL as a “variable speed router.” Should get a higher price for it that way.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View RussellAP's profile


3103 posts in 2254 days

#4 posted 03-10-2013 05:53 AM

Have you checked the switch to see if its dusty, it could be a bad connection there.

-- A positive attitude will take you much further than positive thinking ever will.

View jm540's profile


150 posts in 3387 days

#5 posted 03-10-2013 05:58 AM

buy my festual 2 1/4hp plunge on the cheap till figure it out 423 333 9766

-- jay Rambling on and on again

View jm540's profile


150 posts in 3387 days

#6 posted 03-10-2013 05:59 AM

or my frued 3 1/4

-- jay Rambling on and on again

View MrUnix's profile


6598 posts in 2167 days

#7 posted 03-10-2013 06:01 AM

Sounds like an electronic speed control board that has gone south..


-- Brad in FL - In Dog I trust... everything else is questionable

View Shawn Masterson's profile

Shawn Masterson

1325 posts in 1916 days

#8 posted 03-10-2013 02:02 PM

I had a variable speed Dewalt I got at an auction for 2$. when I turned it on it was stuck on speed 3 witch was to slow. when I was playing with it I found the speed controller was bad. there was a magnet that the speed sensor read, so I broke the magnet off the shaft and it was good to go. I hind sight I should have gotten a sensor, but I have never needed to change the speed of my routers. you my want to do some investigating.

this is just the path I chose it my not be the one for you

View knotscott's profile


7980 posts in 3343 days

#9 posted 03-10-2013 02:26 PM

As others have mentioned, it sounds like the speed controller is shot (or dirty), assuming it has variable speed. As a first fix, I’d try blowing the dust out of it and see if it helps. If not, if it does have variable speed, you may be able to bypass the speed controller and run it as a fixed router if parts aren’t available to you. If that’s successful, you could always add an HF outboard speed controller for ~ $15.

-- Happiness is like wetting your pants...everyone can see it, but only you can feel the warmth....

View EWJSMITH's profile


156 posts in 3794 days

#10 posted 03-10-2013 02:58 PM

Thx guys. It is variable speed and the fluctuating revving happens at all speed settings. I’ll take a look at the speed controller dial and see if that needs a cleaning. I’m not overly concerned if I have to toss it as it only cost me $99 when I bought it and it has indeed served me well – I’ve never had an issue with this and I’ve used it a lot. I have another Makita fixed base router that could mount in the table and just invest in a new good quality plunge router for freehand use.

jay – i’d definitely take you up on your offer and purchase one of your routers (or maybe both) but the cost to get it shipped to me way out on the most Eastern point of North America would negate any savings over purchasing a brand new one locally :-)

View DS's profile


2894 posts in 2388 days

#11 posted 03-11-2013 05:07 PM

If the speed control is done with a potentiometer, they are notorious for getting dirty on the contacts and behaving just as you described. Blowing it out with air is good, but working the dial back and forth across its range will clean the contact areas some too.

If that doesn’t work, then a new part might be required.

-- "Hard work is not defined by the difficulty of the task as much as a person's desire to perform it.", DS251

View oldnovice's profile


6773 posts in 3335 days

#12 posted 03-11-2013 06:12 PM

DS251 is correct, it could be a dirty pot causing speed fluctuations! You can also buy some pot cleaner from StewMac which should also help alleviate the problem.

-- "I never met a board I didn't like!"

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