PM Sensor value is always -1

[Will]

Hi!

I just purchased a kit and set it up with the default instructions for 4.2. Once it started up, I noticed that the PM value is always -1.

I’ve tried to do some debugging by testing the cable wiring voltage against the ground which seems to give the correct voltage of 5v,0v,0v,3.3v,3.3v starting from the red wire on the cable. Attached photos to show this.

The rest of the sensors seem to be fine with co2 and temperature. Would folks be able to help debug? I’ll also continue investigating.

[Will]

I can only attach one image per post.

[Will]

Showing the orientation of the female connector.

[Achim_AirGradient]

@Will i cannot see an obvious error but please try the following.

1. reflow the solder points on the PM connector and the D1 mini (on the D1 itself and on the pin headers on the PCB)

2. please check if you can hear/see the fan in the PM module spinning

3. did you try and debug and see if you see an error

[Will]

@Achim_AirGradient thanks for the reply! I found the issue - the red cable pin seems to be having some issues. I’ve flipped it and I’m starting to get some values which is a great sign!