Mini Auto Level False Touches

My mini is exhibiting the same behavior as in that video. Im trying to do some troubleshooting to see if my rambo board is toast or not.

Im concerned because if i do a continuity check between the nozzle and any of the leveling pads my meter is always showing that there is indeed continuity at all times. Is this correct or is this indicative of a blown board?

Can’t answer whether that continuity is “normal” – because you’re measuring through the board’s sensor circuit, not looking at what the board sees. But what matters is whether the board sees continuity between the inputs wired to the nozzle and bed. You can check that using the M119 command to see what endstops are “triggered”.

If only Z-min is triggered when it shouldn’t be, then you may have a wiring short (but more likely it’s the board). If you have multiple endstops triggered when they shouldn’t be, it usually points to the board because it’s unlikely for multiple wires/switches to go bad simultaneously. Any history of using a wire brush near the nozzle also increases the chance that it’s a blown board.

See these threads:


It should be open to the nozzle/washer otherwise it thinks it is hitting the washer already.

No endstops triggered but I did some prodding with my DMM and theres no voltage on the negative pin of the Z- min endstop socket on the rambo, where theres 5v on all the other endstop socket negative pins in refrence to S. Im taking that to mean its toasted unfortunately. Pretty sure I managed to wire something wrong when i was installing my new e3d tool head.

Thanks for the help

It is odd to have that behavior (probe not reaching washers) if no endstops show triggered… If M119 says Z_min is “open”, then that’s what the firmware sees… And I would expect the nozzle to continue downward to the washer (or past it, if Z_Min never triggers).

But yes, there should be +5v between nozzle and washer. If there is not +5v between the pins going to nozzle and washer (with wires disconnected, to eliminate any possible short dragging down the voltage), then there is something wrong with the board. In absence of the endstop showing “triggered”, I would still expect that missing voltage to cause the opposite problem (i.e., pushing down too far, rather than not reaching the washer).