How to test if Z probe is making a connection

I have a feeling there’s a problem somewhere in the wiring of my Taz 6, but I’m not sure what the best way to test this would be. Any advice?

You’ll need a multi-meter to check continuity in a few places.

Put a probe on the extruder nozzle and another on the “zero sense” wire. This wire is located on the heat-block (hot-end) of the extruder. The wires attached to this block include the heater-cartridge (two wires connected to the brass lug and these are the thickest wires on the block), the thermistor (another probe connected to the block … also two wires but they are thinner), and lastly the “zero sense” wire. This is a single wire (not a pair like the other wires).

Make sure that when you put a probe on that wire connector and another on the extruder nozzle that it reads less than 1Ω.

Do the same for the bed washers. There’s a wire on the under-side of the bed plate (the metal plate). It’s difficult to reach that wire without flipping the whole printer on its side – but since all four bed washers are electrically connected to that metal plate via the screws that hold them on, make sure that if you probe any two washers, nothing reads higher than 1Ω. If a bed washer wasn’t snugged down… that would cause the trouble.

If all of that is good… then it’s possible you have a damaged wire. Remember… the bed probing is a very simple continuity test where the nozzle touching the washer closes the circuit.

This is an open-source hardware printer and that means LulzBot publishes everything you would need to know.

For example, here is the wiring instructions for the board:

And here is the schematic:

It looks like the Zero-sense wire is “patched” to work.


I’m not certain of this so you might want to call LulzBot Support to confirm it… but it looks like it’s tied to the board at EXT1-MX1 (see that diagram on page 1 or 2 of the control box wiring diagrams.) But once you identify the correct wires, you can test continuity to make sure they aren’t damaged.

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