Phillips sonicare toothbrush keeps turning on by itself and function lights stopped working

My flexcare began randomly turning itself on about a week ago. When charging it would vibrate a pattern of one short, then 2 short bursts. After talking with tech support and finding my flexcare was out of warranty, fixed it myself.

I opened the the base with a flat head, disconnected the battery (my model did not have a soldered in one) and wiped out the condensation in the housing and on the brush. I put it back together and it works as before. YMMV

Here is how I fixed the problem: I removed the bottom cap of the toothbrush by inserting a large flathead screwdriver in the slot/hole in the bottom and twisted to left until the cap popped out. Make sure your screwdriver is wide enough to fit in the slotted groves or you will strip it. I then slid out the brush assembly and did notice there was moisture and even some corrosion on the board under the ON button. I dried the assembly off the best I could then I used a can of electronics cleaner from RadioShack. This will displace any moisture and clean any corrosion buildup. I sprayed it liberally one component at a time. The buttons, all the chips on the board, the charging coil at the bottom and even the battery contact. It dries very fast. I repeated this a few times. When I sprayed the on button, I repeatedly pressed it on and off to work the cleaner in. I dried out the inside of the plastic case before I slid the assembly back in place. Then then pushed the bottom cap back in until it snapped into place. This was easy and does not require a tool. It is now fixed and no longer starts on its own or pulse while on the charger.

Update to my original solution. Six months after my original fix my brush started to become very difficult to turn on. The main problem with theses brushes is moisture getting inside the brush handle and damaging the electronics. My original solution fixed the issue but did not address the moisture. I took my brush apart once again and cleaned it with electronics cleaner from Radio Shack. I then applied clear dielectric grease (Get at any auto parts store ) to both buttons on the main board that control the settings and on/off function. I pushed the buttons repeatedly and kept reapplying the grease to work it in.This will displace any water and protect the buttons from moisture moving forward and prevent any future corrosion. I then lubed the O-Ring at the bottom. And before I re-assembled the toothbrush I applied a ring of clear silicon over top of the rubber boot at the top of the brush. I then snapped the brush back together and let the silicon dry completely before using. The silicon should help make a better seal keep out the moisture and if any gets in the dielectric grease should protect the buttons. The brush is back to 100% operational and hopefully will not have any more issues for a while.

The average lifespan of a Sonicare toothbrush, according to consumers, is anywhere from two to five years

I cured my sonic toothbrush from turning itself on by removing the soft plastic cover of the on/off button . I then aimed my hairdryer down the hole from about 4 inches for 2 to 3 mins. I then left this cover off for a few hours before replacing it. It's working fine now and not turning itself on.
I will, from now on lay the brush down after drying the handle well after use. That way water is less likely to ingress via the on/off switch.

I own an HX8910. It recently began turning off while brushing and on when standing on counter. I attempted to remove the insides as many have suggested but It won't budge. I don't want to risk breaking it and having to buy a new one - Cha Ching! But if I have to I will but probably not a Sonicare. I should get way more use than a year and a half. Any suggestions or tell me how much pressure I need to exert to get the inside out would be appreciated.

The switch is worn out and there's no fixing it. Sorry, but you'll have to get a new one (although I think Phillips is counting on that).

Over the last few weeks, my Sonicare Diamond Clean began to turn itself on and off, as described in other posts, like Morse code. Then a couple of weeks later, it would turn itself on and run for many minutes at a time.
I managed to slide the internals of the unit out from the bottom (no tools required), just placing the unit upside down, and firmly pushing down on the housing until the internals pushed out from the bottom of the unit.
Once the internals were separated from the housing, it was clear Sonicare has a design flaw with this brush system, as water must seep down the top seal and into the internals while it sits in the charging base.
My unit was very wet on the inside, with lots of corrosion on the circuit board. I left the unit apart overnight to let all the moisture dry.
Next day, Using about ½ can of CRC QD Electronic Cleaner on all the electronics and battery connections of the unit made a visible improvement to the corrosion problems.
Put the unit back together again, and it appears to be charging and working as normal.
Lesson learned to extend the life of my Sonicare Brush is after each use, remove the brush head, and dry the top post with a towel, to reduce the opportunity for water to seep down into the unit while it in the charging base.
Thanks to all who have previously posted, because without the knowledge, I would have otherwise just gone to Costco and purchased a new one.

This is happening to mine, as well. I had to put it in the garage to get some silence. I called Phillips Customer Care and was told it is out of warranty. No help and no suggestions. I bought it from my dentist's office about 3 years ago.
Thanks for the fix suggestions...will try that.
I am very dissatisfied and disappointed with Phillips Customer service and support. Those toothbrush es are very expensive.