Ryobi 40V Mower Cutout Fix

I’ve had my battery-powered 40V Ryobi mower (model #40108) for a year now and have been pretty happy with it.  However the last time I used it the damn thing would randomly shut off while mowing.  At the time there didn’t seem to be any rhyme or reason to the problem such as heavy grass or a weak battery which was reading 2/4 bars.  I threw the battery into the string trimmer and it worked great.

So I took the lovely slime-green plastic cover off to see if there was anything obviously wrong.  My hopes were low because I figured the mower would consist of a motor and control board.

Simple mower internals

Sure enough nothing looked wrong such as a leaking capacitor on the control board.  But while putting it back together I noticed a kill switch I had never noticed before!  It’s located by the handle hinge, ensuring that the mower will only run while the handle is in the folded-out position.

This little switch was flopping around in its hole because one of the spring clips on the backside was broken probably while I was removing that slime-green plastic cover.  When the handle is folded out the switch is depressed, closing the circuit allowing the mower to run.

If you take a close look at the interaction between the switch and handle, it is  not a precision operation.  Due to the position of where the switch happens to be, the handle bumps into it, hopefully depressing it.  Here’s the root cause of my problem: The mower’s frame had loosened up over time, allowing the frame to rack from side-to-side during turns.  This racking let that little switch spring back up, opening the circuit and stopping the mower.

And thankfully the solution was to tighten these two T25 frame bolts, located right above the rear wheels.

Keep these bolts tight

And as a footnote, I bypassed that dumb switch just to avoid this kind of nonsense in the future.  The connection was wrapped up with electrical tape after these photos were taken.

I hope this short article helps someone out!

47 thoughts on “Ryobi 40V Mower Cutout Fix

  1. This information helped me. The plastic handle clamps need to be securely fastened. I hope these plastic clips hold up over time

  2. Thanks for taking the time to write this! My mower was having the same intermittent issue. Yanked that switch out and hardwired it as well.

  3. After a few uses, my mower did the same thing. My Google searches all provided the same resolution you provided. I removed the cover of my mower and bypassed the switch. I went back to mowing and after a few minutes, the mower would cut off again so obviously the problem wasn’t the side handle switch. I opened the handle assembly where the bale and start lock switch are. I found that there is a small lever on the bale that engages the main power switch. The bale had enough play from side to side that the lever would not always press hard enough against the switch and the motor would shut off. With a lot of movement of the mower this would happen repeatedly. I tied a narrow cable tie around the end of the bale before it exits the handle casing and widens where the switch lever is to keep it from moving side to side. After reassembling the handle case it tested fine. No more spontaneous shut offs.

    1. do you happen to have a picture of where that lock switch and the zip tie location is? im having similar issue , i actually did the bypass at the bottom(per the thread) and also a fix on the upper handle (by pass gray handle and gray button) but i suspect my issue is in the middle part where it locks. i was actually able to get 1 full session in without it cutting out but to my surrpise when i try to turn it on today it shut off after turning on in 3 seconds lol…..

  4. I’m having the same problem with my Ryobi. No matter how many shims I put between the handle and the red button, it still quits.
    Can you tell me how you disabled that shutoff switch?

      1. Thank you David the bolt tightening you explained in the original post solved an issue that I just experienced!

      2. I TRIED TO TIGHTEN the two bolts with an Allen wrench but only one could be tightened a little, There is jjjust the. Two on the left side of the mower( When You are standing behind the mower and hanging onto the handle I am referring to the left side of the mower. It worked good for 2 minutes and then shut off again

      3. Hi Dave
        My problem is the same only with the self propelled wheels. Mover moves forward then stops moving. Headlight also shuts off at the same time I replaced the micro switch any ideas?

  5. Great info. I put a piece of cardboard between the handle and the button and it worked just fine. Next project will be to splice the circuit closed, until cardboard!

    Thanks for the assistance.

  6. I am having the same issue, but I have the 20″ smart trek self propelled version. There is no red safety sensor along that bar. All other models seem to have it except mine. (I’m assuming it’s newer and they removed it after all these issues people are having). The manual only mentions a tilt sensor, but doesn’t say where and it only activates at a 45 degree angle. Please help! Model number is RY40LM03

    Thanks in Advance!

    1. If you figure out how to reliably reproduce the problem you should have an easier time of figuring out the problem. It is might be frame flex caused by loose fasteners

  7. My problem is with the propulsion system. While I can get power to the blade fine, when I pull the levers that are supposed to propel it, the lawnmower jerks forward then stops. The blade continues to get power. Any suggestions would be appreciated. Thanks.

      1. Nope, I’ve just been pushing it around like a pushmower. I may try to take it apart at the end of this season and test the circuitry, and if I do and find anything I’ll let you know through this website. Pushing it is not a big issue for me so I can wait till the last blade is cut.

        1. Ok Thank you for your response I will do likewise. So far I took the entire transmission apart everything looked ok I changed the micro switch in the upper handle. I’m going to look at the circuit board because my headlights cut out at the same time my mower moves slightly forward

  8. I have not used my new Ryobi lawnmower yet. The first time I used it the lawnmower starts and stops frequently. All the troubleshoot items were not the issue. I have the grass cut level on the highest level. The bolts on the side near the handles are tight. Any ideas?

  9. Help! I think I have a new model as well. 40v Brushless manually propelled. Bought in April from Home Depot. It cut off yesterday while mowing. The grass was a little wet as the sun had not hit that side of the house yet. Other than that I don’t know why it cut off. I don’t see the red button on the side and I’m not sure how to take the top off to investigate further. Any suggestions? Thanks.

    1. There are 12, I believe Torx #20 screws that hold the top cover and front bumper on. Removing them and then replacing the cover took more time than the fix. Also, the cutting height adjustment knob has 2 small Phillips head screws holding it on. Be careful – they are easy to drop and possibly lose.

  10. Had the same problem with my 1 year old Ryobi 40v push mower yesterday. A Google search brought me to Dave’s fix and…sure enough…it was the fabled red button switch. Jumpering the two wires together fired the mower right up, so I just spliced them together securely and went back to working and slaving over a hot lawn.

    Thanks, Dave!!!

  11. Thanks! That did the trick! Glad I started looking on line before I dove in with tools. It became a two minute fix.

  12. This worked. Because the spring bolts on the handle are difficult to pull out, I thought I’d leave them out since the handle seemed stable. After I turned spring bolts to secure handle, the mower worked. Thank you!

  13. Hi, it is very nice to find your post. I loved the way you described everything with neat and clean photos.

    I think I can do my own mower maintenance from now on. Thank you for sharing with us.

  14. Many thanks for the advice, my issue is a little different. My 5 amp battery runs everything else fine but the mower drops down to very’ rough’ low power running or cuts out? I am not sure if it is the battery or the mower.

  15. Great post. Does anyone have this problem. The grass catcher is lowered into two slots, one on each side of the mower. The slot on the right side forms a circuit when the catcher is in place. My problem is that the catcher won’t stay firmly in the slot thereby causing the mower to quit. Once you replace the catcher, the mower starts right up until you hit a bump and lose power again. Anybody have a fix?

  16. Thank you so much for this!!!! i just inherited a “Broken” mower and this fixed it right up. Thank you so much. Also, Have yall run across any mods to get a 6AH battery to fit in this bad boy? the battery is physically too big but the extra AH would be awesome. Also its the only size I have…..

  17. I have bypassed all 3 safety switches. Use the fuse key as the starter. Starts right up lights come on than in less than a minute comes to a sudden stop. 40 Volt cordless. Ready to trash

  18. I am not sure if this is the same problem I am having, when my Ryobi mower was new, it just did well with any height settings i use, I normally want to put it to the lowest so that I can maintain the grass low.

    However, after a year, I noticed that whenever I use the lower settings, it seems that the motor had a hard time cutting the grass now, and slowly stops. This doesn’t happen when I put the settings at third height level. I tried to change the blade thinking that it might be dull, but it did not solve the problem. Any suggestion that you may provide what I should be looking for here to fix the problem?

  19. Thanks for posting this, a bit of gorilla tape over the switch and I was back in business. Will do a more permanent fix when I get a chance.

  20. You are a genius! Saved me a ton of time, tightened those screw and I was back to mowing in 30 seconds.

  21. i have a Ryobi 40 v brushless mower and the self propelled function has been acting up.
    The wheels make a clicking noise and the wheels lock up. Do you have any fix for this ?

    1. I don’t have that model, still using the basic one in this post. Maybe someone else will chime in!

  22. Same issue on a mower that is only a few months old. Has Ryobi offered any input to what is obviously a design or manufacturing issue? Seems this could be a large warranty claim issue for them

  23. My Ryobi 40v mower would only start (maybe) 1 out of 10 times, and would randomly cut out while mowing. I replaced the red key with a bare wire, and that fixed it. The contacts get pushed into the lime green cavity, and don’t make contact with the key.

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