# Probe stays active even with cable disconnected

**URL:** <https://forum.avidcnc.com/t/probe-stays-active-even-with-cable-disconnected/5602>\
**Category:** General Chat\
**Tags:** touch-probe\
**Created:** [December 28, 2025, 10:47pm UTC](https://forum.avidcnc.com/t/probe-stays-active-even-with-cable-disconnected/5602 "2025-12-28T22:47:43Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Doug\_Crow](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/doug_crow/32/6108_2.png) [@Doug\_Crow](https://forum.avidcnc.com/u/Doug_Crow)\
**Post date:** [December 28, 2025, 10:47pm UTC](https://forum.avidcnc.com/t/probe-stays-active-even-with-cable-disconnected/5602/1 "2025-12-28T22:47:43Z")

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PRO4896 4’ x 8’ CNC (December 2018)

NEMA 34 CNC Control System

2.2 kW Spindle / VFD System

· Touch plate sensor would not activate.

o Disassembled plate to rewire. (As I have done several times before)

o Noticed MACH4 probe signal was “ACTIVE” without the connection being made.

o Noticed machine would not jog.

o Restarted computer and machine, same problem, machine will not jog.

o Disconnected the probe cable from control box, MACH4 still shows probe active.

· History reads:

o _Limit switch Y – tripped!_

o _ESS: Limit Switch triggered on Motor Limit 3_

§ Tested all limit switches, all switches lit with metal contact.

§ Disconnected and reconnected all sensors one at a time to make sure it was not a connection issue.

o _Can’t jog toward Y – limit!_

· Machine will not HOME.

· When “AXIS LIMIT OVERRIDE” is on machine will jog in all directions.

· Noticed the belt was worn on the left y axis motor. Replaced belt. (Do not think this has anything to do with the issue but needed to be replaced.)

· Released the y-axis motor springs to make sure I did not have them too tight to move, same issue.

· Swapped y-axis sensors with x-axis, same issue. (_Limit switch Y – tripped!)_

· Swapped y-axis sensor cables at control box with x-axis, same issue.

· Under the MACH4 diagnostics tab, Homing Sensor Y2 and Limit Switches Y2— are blue. All other switches turn blue when testing. Input Signals Probe is blue.

· Ran machine all day yesterday without any issues.

 ![IMG_3814](https://canada1.discourse-cdn.com/flex027/uploads/avidcnc/original/2X/8/8877b688ea7fe90e8c0183f9d62a631d061f2c47.jpeg)

 ![IMG_3812](https://canada1.discourse-cdn.com/flex027/uploads/avidcnc/original/2X/9/9a2b2d3dce43e2731f001a4d4fc8eda2303d3355.jpeg)

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<div class="post-metadata">

**Author:** ![Doug\_Crow](https://yyz1.discourse-cdn.com/flex027/user_avatar/forum.avidcnc.com/doug_crow/32/6108_2.png) [@Doug\_Crow](https://forum.avidcnc.com/u/Doug_Crow)\
**Post date:** [December 31, 2025, 7:08pm UTC](https://forum.avidcnc.com/t/probe-stays-active-even-with-cable-disconnected/5602/2 "2025-12-31T19:08:55Z")

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![IMG_E3826](https://canada1.discourse-cdn.com/flex027/uploads/avidcnc/original/2X/4/4e83ed0272b7cfd35aea215e2e9435857b10b9dd.jpeg)

If anybody else has this issue, look on your CRP860 board for burn marks.

Ordered a refurbed board for $70ish +shipping, got it next day, back up and running!!