Canon 600EX-RT won't turn on at all

[jimlopes]

I own two 600EX-RT speedlite's.  One of them hasn't been used much and is totally dead.  I tried half a dozen different batteries and won't turn on.  

My 2nd speedlite turns on, but sometimes it doesn't.  The led screen sometimes is looks like it half on.  So this flash is proving to be unreliable on a shoot.

Canon has stopped supporting this version so I can't even get these repaired.  Is there a reset button on the device or anything else I can try to revive them?  Thanks

[jimlopes]

So I was about to put this flash to bed after trying everthing suggested here and not being able to send in for repair.  I decided to just hit the flash a couple of times of the side of my hand.  Figuring the old school way of trying to getting something to work.  Well, it actually worked and the flash fired right back up!  I couldn't believe it... could there been a connection inside that was loose?  What could explain just hitting it a couple of times for it to work again?

[normadel]

Sure, could be a connection somewhere. Battery terminal connections that you can't see, for example. Don't know how you can tell without opening up the flash, though, which I'd be very cautious about doing.

[rlhdpcetc]

Jim, you saved the day. I have two of Speedlite 600 EX-RT flash units and both were malfunctioning. A quick whack on the left side (if your looking at the screen) brought both back to life. I had already tried a whack on the right and it didn't work. A day later and they are functioning as expected. My battery terminals were clean, there was no corrosion in the housing, and I had fresh batteries. The ole whack technique worked like a charm. Thanks!

[dpastern]

Having this issue myself.  Purchased a used unit from keh.com in the first half of 2023.  Tested it when I received it and it was working OK.  Tested it again around a year ago and same.  Haven't used it properly, just 2 tests.  Went to use it today properly and it's as dead as a door nail.  Contacts look clean, but I'll try the WD-40 option tomorrow.  Was not stored with batteries.  I tried the whack option just now, no go.  Still dead as a door nail. 

My utterly horrible 2025 continues to just get worse day by day (I've had a true annus horibilis).  

I have emailed my contact at Canon, but reading in this thread that it's no longer serviced by Canon will mean it's probably dead for good and just rubbish now.  

Dave