Taz 3 to 5 - Stumped

I bought a Taz 3 and love it! If something happened I was going to upgrade it to the 5. No hurry to upgrade so I started collecting the parts. Early this summer I checked on a print in progress to find the dreaded lump of plastic around the extruder with a half printed piece… Time for upgrade! Yeah!

Power supply is 24 V.
New LulzBot TAZ Single Extruder Tool Head v2 (a work of art)
New bearings, linear and axial
Fabricated new harnesses (Only got 8 pins backwards!! :unamused: )
Note: My old NAPA NW 726603 crimpers worked much better than the ratcheting crimper I started with.

Loaded Firmware and the z would not move ether direction and the y would not move away from switch it also said the y switch was closed when it was not.

Assumed the board was fried so I ordered a new RAMBo 1.3…Flashed… Switch problem went away. I am ready to burn in the Z but I get no Z or Y movement.

Any suggestions?


You will want to check and verify the connections against the OHAI documentation and make sure you got everything in the correct location, and have the endstops rigged the correct way (normally open vs. normally closed, etc. ) You may have to hit the home all axis button on some control systems before you can move all axis, but usually you will be able to move Y from the start. You may want to do a continuity check on the endstop wire harness.

When you say “doesn’t move” do the motors make any noise or heat up or vibrate, or do they just do nothing at all for those axis? if they are making noise but not doing anything, it may be reversed pins setting the two magnetic coils in the motor in opposition to one another.

Thank you for your help!

I have switches all normally open. M119 verified all are opened after i flashed firmware. Will check build instructions again for proper pin assignments. I also checked for pins that may have shifted within the connectors. All was well. I have rung from board connector to components.

X, extruder, bed heat, and nozzle heat are working fine. SD card reader sees files.

Y growled when I moved it 1MM I have triple checked the board connection. Rang out internal cable, extension connector and that the servo wires matched at the extension. Also double checked internal and external chassis ground.

Z does nothing upon command and rambo flashes red instantly. I can turn Z with fingers with power off - not bound.
I operated temp and move axis from the panel menu, not Cura.

Switched power off when Z did nothing. Didn’t want to make things worse. I was scared to hit home all. :open_mouth: It’s got to be something simple that I’m overlooking.

Using the latest Cura on the latest Mac OS selecting taz5 with proper nozzle, then click install original firmware.


So the green white and red z motor cable (nearest to the enclosure) have conductivity between the pins on the extension. They were shorting out the signals. I made a temperary bypass cable and Z works fine. I guess it’s shorting in the plug with the male pins. Everything looks fine and nothing changes when I wiggle the wires around. Guess who gets to make a new harness! :angry:

I’ll troubleshoot the Y motor tomorrow. it growls and trembles when I try to move it.


Growling and trembling means you have two of your pins reversed in one end on your y axis somewhere along the harness.


I ordered new terminals and made new single run harnesses that travel from the steppers to the board uninterrupted. The shielding from each cable share a common stud for ground, inside the enclosure. Only the extruder harness, power supply in, and heated plate harnesses have quick disconnects.

A friend told me not to install the quick disconnect, because they would only be trouble, and was right; so he unlocked the “Told you so” achievement. :wink:

All axis moved. I select return to home x and z work correctly… it thinks the Y home in 20 mm from the back of the plate. It moves the correct direction, but stops at exactly the same place. Maybe the motor is not clocked in the right position and I should reset the belt position?

I go back to move the Y towards the limit switch 1mm steps and it sounds like it’s moving, but it’s not. I close the switch and it will not make a sound. So the switch is being interpreted correctly by the board, and the board is sending something to the stepper.

This evening I will plug in a spare stepper motor to see if the Y stepper is faulty.



I swapped the x and y leads on the board. The y stepper moved the bed back and forth no problem. X would only move the tool head in one direction. problem followed the port, not the cable.

New board is bad? :confused:

Any chance the belt is reversed and it was expecting to hit the X endstop but was actually going away from it? If the board will provide power to a motor in one direction, the motor controller is working. I’d check the limit switch wiring, maybe replace the limit swich and verify the cable path from the ohai kit pictures.

I unplugged all three switches from the board. Powered off board, restart, M119 reports:

< Reporting endstop status
< x_min: open
< y_min: TRIGGERED
< z_min: open

Remove board and wash with soap and water? :laughing:

The Y belt is routed exactly like step 7 Install Belt section of TAZ 5 Y Axis Assembly Workflow.

I completely removed the board and inspected it for foreign debris and bad solder. Everything looks good except y_min

< Reporting endstop status
< x_min: open
< y_min: TRIGGERED
< z_min: open

When I select autohome everything moves as it should except the Y. The board thinks it’s already closing the switch all the time, regardless of what is plugged into the y_min socket.

I’ve isolated it to the board. Guess I will contact UltiMachine for another one.


It is possible to reverse the endstop open / close trigger in firmware. If you put the switch back on in opposite pin plug for how it should be and attempt to trigger, does it register that way? If it doesn’t, then I would suspect a bad one, but that is nearly unheard of as a failure point so it would be very unusual.

Your help has been amazing, thank you!

Unfortunately I have officially run out of time on this project. I ordered another board from Ultimachine. They have been responsive, but it’s a Friday and no verdict. I ordered another board without their approval. It will all work out. Will update when running.


Threw the Taz 3 board, flashed, it works! Now where did I put the esteps, I thought I had them on my phone…