Anohter No voltage case on S21 header of FTX60GV1B about esp32-faikin

[Sonic-Amiga]

First of all, read this and triple-check.

Hmmm... I see "+12V" mark on the PCB nearby...

[sm-Fifteen]

It's possible you've just plugged it in reverse. I made that mistake when installing mine (there's really no good way to tell the correct orientation on that thing), and flipping it solved the issue with (luckily) no damage to any component that I could tell. I notice 2 capacitors right next to your S21 port, aligned with two of the pins, so my guess would be that these are the data pins.

But from your OP, I take it you've already tried both or tested the pins with a multimeter?

[yiannosi]

But from your OP, I take it you've already tried both or tested the pins with a multimeter?

I tested the pins with multimeter taking into account the possibility of different pinout. I just wish there was a known solid ground to use as a reference on the PCB. I had to partly dismantle the pcb from the rest of the AC unit while standing on a ladder and its not that easy to take measurements with the power switch on...

[Sonic-Amiga]

Oookay, let's assume that we've already checked against stupid things and here go smart ones... Unfortunately that would require more ladder-up-n-down

From markings on the board we can see that GND is JP36 and +12V is JP35. So, we can beep which pin on S21 is ground. Pins next to C65 and C66 indeed look like tx/rx. So, if we line this up with the pinout we know, we'll get:

It's now your turn to confirm a GND pin (or find a proper one) and check whether 12V is present on JP35. Further actions depend on whether 12V is present:

• If yes - you may just clip a tap wire to this jumper i think.
• If not - the hard part comes. We need the schematic. And in order to obtain one, you'll need to dismantle your board and take a good readable photos (or better flatbed scans) of both sides, so that we could correlate them and trace connections.

[revk]

The little triangle denotes pin 1, if that helps.