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ST-E3-RT / 430EXIII RTDropping link


Hi all,

My setup is x1 ST-E3-RT transmitter and x3 430EXII-RT speedlights.

For the last month or so, my ST-E3-RT (ver 1) transmitter keeps dropping links with all 3 of my 430EXIII RT speedlights after the 8-10 mins mark. 

I've tried scanning and assigning them the strongest channel every time I turn them on and the problem is still there. Even when I only turn on one of the 3 units at a time, the same problem persists.

On my tests, I have the units and the transmitter only 1-2 feet apart. But they're still dropping links even when I have purposely turned off the sleep mode.

It's pretty annoying to have to go reset the speedlights every other 10 mins or so.

I didn't have this issue when I first bought them.

Has anyone experienced similar problems? If so, how did you fix it?

Any suggestions or guidance to fix this annoying issue will be greatly appreciated.

Thank you!




Product Expert
Product Expert

Hi there,

What camera are you using these with, and if multiple cameras are being used do you notice a difference depending on which camera has the transmitter mounted?

I’m using the 90D. But the issue is still happening even when I do the testing with the ST-E3 not mounted in the camera.

I’ve even tried using one of the 430EX III RT as the master. Same issue. Link drops after a few minutes regardless.

By the way, it drops link no matter how many speed lights are linked.


Try posting this on DPReview and Fred Miranda forums as well. 

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic

Good idea!

Can I please  have the link for that forum?

Legend and 

There are various groups; you could see the best one(s) to post into.

John Hoffman
Conway, NH

1D X Mark III, Many lenses, Pixma PRO-100, Pixma TR8620a, LR Classic

Thank you! - I will check both of them out.


Following the 600EX-RT dropping link post elsewhere on the forum, can I ask if you have changed the ID of the ST-E3-RT and 430EX III-RT from the default 0000? Another poster found that when they changed the ID from 0000 for their ST-E3-RT and 600EX-RT / 430EX III-RT setup the dropped link problem stopped.

Brian - Canon specialist trainer, author and photographer

Yes. I’ve changed the IDs and problem still exist.

i’ve tried changing channels from auto to the strongest channel after scanning with no luck. 

is there any firmware update out there for these speedlights or transmitter?

Yes there was a firmware update for the St-E3-RT in 2015, but it had to be done by Canon.

Ultimately it depends on the serial number. 

If the serial number of your ST-E3-RT is [xx01xxxxxx] ~ [xx03xxxxxx] then you may need the update. If your ST-E3-RT is in that serial number range, open the battery door and see if there is a white painted dot above the batteries and towards the battery door hinge, if so then the unit has had the update done. 

ST-E3-RT doesn't have a USB connection so firmware has to be done in the Canon service centre. 

The Speedlite 430EX III-RT can be updated from a camera - much like a camera firmware update - but as far as I know there has not been any update released so far.

Brian - Canon specialist trainer, author and photographer