IKEA T1828 "Gunnar" not able to pair anymore. Works fine with many other IKEA devices.

[KaHeMu]

I have been using Z2M for almost five years and have around 90 Zigbee devices in my house. Cool project! Recently I wanted to re-pair a few devices because the coordinator check (https://www.zigbee2mqtt.io/guide/usage/mqtt_topics_and_messages.html#zigbee2mqtt-bridge-request-coordinator-check) indicated that they dropped from the coordinator memory. Re-pairing worked fine for most devices except for my Tradfri Gunnar (https://www.zigbee2mqtt.io/devices/T1828.html), i.e. after removing it from my network I cannot reset and re-pair it anymore regardless how hard I try. Still I can connect a Ikea remote control with the T1828 directly (by pressing the pairing button of the remote for >10s) so the T1828 hardware isn't broken but for some reason it does not connect allow to connect with the Z2M coordinator anymore. (After 6x on/off according to the instructions the T1828 doesn't reset or start the pairing process). Other IKEA bulbs I use still work fine and can be re-paired the same way without any problems.

I tried to pair it in vain with my Z2M v.1.36.2 installation as well as a brand new v.2.0.0. No difference.

Has anybody experienced the same with any IKEA LED device that it doesn't properly reset and re-pair anymore?
If the T1828 wasn't a ~90 EUR ceiling light I would simply throw it away.

[chris-1243]

I had an IKEA LED2107C4 which shares the same reset procedure. It was quite complicated to reset it in order to pair it again. It took multiple tries each time I wanted to pair it...

Your light should blink when it enters in pairing mode.

Strictly follow the procedure described in the link you provided

[KaHeMu]

Of course I tried the reset procedure multiple times without success while it works with other IKEA LEDs perfectly. There is simply no reaction, i.e. no blinking/breathing after the 6 OFFs and ONs.

[chris-1243]

Have you tried 7 ON/OFF ? As suggested in the pairing procedure ?

It looks like the same kind of nightmare I had while pairing the light I mentioned...

[KaHeMu]

Yes, of course I tried with 5x, 6x, 7x, with different adapter types and different Z2M versions (v1.36.2 and v2.0) on different days and different location. The T1828 ignored all of them but still reacts properly on a Tradfri remote control binding attempt. So it is not entirely dead.

[chris-1243]

What works is to use (very) short “on’s” and a little bit longer “off’s”, where you kill the light as soon as the bulb shows signs of turning on. Start with bulb on, then off, and then 6 “on’s”, wait in the 6th ON state. (If you try play safe and go for 7 "on's" the reset sometimes fails.)

I read too fast. 7 cycles on/off are not a good idea. Stick to what it is written in the pairing note.

Your light is able to pair. It seems not reset correctly. Stay calm and cool and try the reset procedure

[KaHeMu]

I tried for hours with anything you could think of within the limited degree you have with a simply on/off switch. Nothing worked. But here is the trick (caution: very invasive): I opened the T1828 entirely until I could access the tiny Zigbee module inside the LED controller. I connected the Vcc and GND solder joints of the Zigbee module with an external 3.3V lab power supply and then ran the 6x off/on cycles with the external power supply. Voila it worked at the first attempt. I guess the T1828 power supply has become a bit slow when turning off (due to large caps or so) and so its Zigbee controller doesn't properly identify it as reset. Issue resolved.

[chris-1243]

Quite invasive but glad it works for you.👍