Mini 1 Leveling Failure

I have tried a few seperate tricks to try and fix this issue but I am truly unshure of where to begin…

It wil contact the first corner, retract about 1cm and then repeat for the fine touch. Moves to the second corner and contacts the washer, and continues to press almost tweakign the bed, then retracts like it has not made contact and repeats the nozzle clean step.

Here is a video of what it is doing

I have tried to clean the extruder nozzle, replaced the extruder nozzle, tried changing the washer, measured the resistance between the head and the washer (all were the same), uninstalled CuraLE and reinstalled, and even the basic of unplug and plug it back in…

Any help would be greatly appreciated. I am new to 3D printing and new to Lulzbot…

Be sure you are measuring the resistance with where the plate would be during normal operation. It could be you have an internal break in your bed wire, where it is connected when probing the rear left washer, but when it moves to the front right washer this wire no longer has continuity. This would be my first suggestion for you to check and replace if needed.

Take a volt meter between the nozzle and a selected washer. That is with the machine turned on. You should see about 5V. The washer is connected to ground and the nozzle is connected through a long wire directly to a pin of the microcontroller on the Rambo. Bad design.

There are no safety resistors, diodes on the board. Just the tiny diodes in the microcontroller. The firmware enables weak pull-ups which is a tiny transistor that acts like a 40K Ohm resistor to the 5V supply.

You can wiggle the bed around (forward and back) and see if the voltage goes away. If it does, you have a flakey wire.

I forget the g-code command but if you search for it you can read the state of the limit switches. The bed leveling logic acts like the Z limit switch. You can take a wire and short the nozzle to each washer and see if the input pin to the microcontroller is toast. In your case it seems that the controller is fine as it works for one corner.

I changed to a stainless steel nozzle and used brasso on the washers to polish. Also, you can rotate the washers 20 degrees to present a new surface. I also changed my end G-code to retract at the end of a print and my machine works way better. I had leveling fail every time before digging in. It is ugly when it stops working so I feel for you.

I found the command which is M119