Hi Alain, Today I have been the same problem than you, Alarm 4 & Error 9 with the Probe. After 2 hours of trouble, I solved the problem by reversing the 2 wires on the probe. Black instead of red and red instead of black. And now no alarm et no error, and the probe process is OK. Hope this helps A+ Robert
That masks the problem rather than solving it. If you have a connection between mains EARTH and DC GROUND you have a potentially dangerous fault. Please read the whole thread, especially the posts from @Peter Van Der Walt. Alex.
Hello Alex, My language is French, I hope my English is clear enough. I investigated with my multimeter. I don't have any electrical shorts between GND (DC) and EARTH (AC). But by mistake I had connected GND (DC) to the chassis of my DYI CNC. And as I hadn't connected EARTH (AC) to the chassis, I didn't have an electrical short. I removed this electrical connection (GND (DC) <--> CNC chassis). But I have to make the EARTH (AC) connection to the CNC chassis to be safe. My CNC controller is Arduino UNO + CNC Shield 3.0, in this configuration the probe works only if the plate is connected to the signal and the magnet/clamp to the ground. If I reverse these connections, the probe doesn't work. I have found on several forums that the probe works only in this connection configuration with Arduino UNO + CNC Shield 3.0. Please note that this isn't the OpenBuilds probe, but a probe without the LEDs. If you have any comments, please don't hesitate. Here's where I am for the moment. A+ Robert
If the probe does not work in the proper configuration {magnet to signal and plate to ground}, then the shield circuitry is maybe where the problem lies. I assume the shield you have is a 4988 driver board {3D printer}? I don't know what the your shield circuitry is like but the probe base wire must go to Arduino ground pin, and the magnet/clip wire to Arduino pin A5. You should also fit a 10k resistor between the probe clip connection {A5} and the 5v pin on the Arduino..
Also, the grbl 3.0 boards have been obsolete for a long time and the z probe pinout is different than what grbl 1.1 uses. I really wish certain companies would quit selling that board and claiming it is grbl compatible. They should at least point out that you have to use a really old version, or that you need to swap a couple pins. Connecting Grbl
