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Analog Sensors - Troubleshooting Guide - NGC

Last updated: 06/13/2025

Analog Sensors - Troubleshooting Guide - NCG

Revision A - 06/2025

Analog Input Troubleshooting Video

The following service video provides information on troubleshooting analog inputs.

Note: This service video is for reference only and does not replace the written procedure. 

A Haas machine, depending on the vintage, has anywhere between one and eight analog sensors in various systems throughout the machine. All of these sensors share a common ground. A problem with one of these sensors could potentially affect the signal from all of them, making troubleshooting difficult. If you are troubleshooting a problem with any of these sensors, their cables or the Maincon/ I/O PCB follow these simple steps:

  1. Look at the gauge page and identify the readings that look unreasonable. For example, if the spindle motor temperature [1] reads 0-degrees Fahrenheit and the shop is at 77-degrees this is not reasonable.
  2. If one of these cables or sensors has a short-circuit. The gauge display will show several readings that are not reasonable.
  3. Unplug each analog sensor one at a time. Look for the other gauge readings to return to something reasonable.

     Note: Some signals may take up to 30 seconds to react.

  4. When you find the sensor that is causing the inaccurate readings you have most likely found the problem. Check the cable for damage. Check the sensor.

     Note: The cable or the sensor are more likely to be the cause of the problem than the Maincon / I/O PCB.

Symptom Table

Symptom Possible Cause Corrective Action
Alarm 120 Low Air Pressure Or Flow The compressed air supplied to the machine is below the minimum pressure or flow required. 

Check for contamination in air pressure sensor. If contamination is found, sensor must be replaced.

Important: Ensure that air supply to the machine is clean and dry to avoid repeat failures. 
Alarm 9916 EXCESSIVE THERMAL COMPENSATION DISTANCE There is electrical noise on the signal or the thermal sensor is faulty. Check the thermal sensor input in diagnostics and see if the signal is fluctuating.  If signal is fluctuating,  inspect the amplifiers and make sure there is a ferrite bead on ALL axis power cables. Check for loose connection or damage to the thermal sensor cable.  If all checks have been done the thermal sensor is faulty.
Alarm 9940 AXIS THERMAL SENSOR FAULT There is electrical noise on the signal or the thermal sensor is faulty. Check the thermal sensor input in diagnostics and see if the signal is fluctuating.  If signal is fluctuating,  inspect the amplifiers and make sure there is a ferrite bead on ALL axis power cables. Check for loose connection or damage to the thermal sensor cable.  If all checks have been done the thermal sensor is faulty.
The cable or sensor is disconnected. Check for loose connection or damage to the thermal sensor cable. 

At Power On:

Alarm 4.9940 AXIS THERMAL SENSOR FAULT

Is generated.

 The I/O Main Firmware is outdated. Make sure the I/O Main Firmware is version 4.09 or higher.  Refer to the I/O Firmware Upgrade procedure.

After software update machine generates 

Alarm 4.9916 / 9916 EXCESSIVE THERMAL COMPENSATION DISTANCE

OR

4.9940 / 9940 AXIS THERMAL SENSOR FAULT

 Invalid I/O configuration files. Make sure that the thermal sensor is mapped to the correct I/O analog input.
This applies to UMC machines:  Axis thermal sensor cable is plugged into the wrong analog input. Make sure the axis thermal sensor cable is plugged into P45 on the I/O PCB.
There is electrical noise on the signal or the thermal sensor is faulty. Check the thermal sensor input in diagnostics and see if the signal is fluctuating.  If signal is fluctuating,  inspect the amplifiers and make sure there is a ferrite bead on ALL axis power cables. Check for loose connection or damage to the thermal sensor cable.  If all checks have been done the thermal sensor is faulty.
ALARM 9941 CRASH DETECTED (spindle head accelerometer)  The machine detected a crash Verify the program machine movements to make sure the machine does not crash
The Accelerometer unit, cable or spindle head CAN board is damaged
  • Verify analog inputs are not 0 (cable unplugged)
  • I/O board minimum version 4.09 (update to latest if possible)
  • Spindle head CAN board minimum 1.10 (update to latest if possible
  • Make sure to take an error report (SHIFT+F3), error reports will have information about the crash direction and magnitude in the JavaConsoleLog.txt file (refer to Crash Detection Section in the Accelerometer Troubleshooting Guide for further information)
ALARM 966 EXCESSIVE TOOL IMBALANCE (board accelerometer) Excessive tool vibration is generated by on board accelerometer Verify that everything is properly balanced, such as tools and spindles

Reduce sensitivity using Setting 245

  • Setting 245 = Normal: Means that parameter 856 is directly used
  • Setting 245 = Low: Means that parameter 856 is multiplied by 1.5
  • Setting 245 = Off: Alarm 966 will not be thrown. 

NOTE: Setting 245 will not persist when the power is cycled

Please refer to the  Accelerometer Troubleshooting Guide for further information
Spindle motor temperature sensor fluctuating Electrical noise around that area. A ground wire should added from the motor lift bracket to the spindle heat shield. Refer to: HSG-N 08-23-2024.

NGC - Analog Sensor Information

Note: The connector location of these sensors can change,  please check the location on the screen.  Press [DIAGNOSTIC] and go to the I/O tab and search for keyword "ANALOG" and press [F1].

The raw data analog sensors that are connected to the Maincon PCB, can be view under the Mocon tab.

Gauge Name / Analog Sensor
 Analog Sensor Location
 Analog Sensor Connector Location*
 Alarm / Warning

Mills: TSC Pressure

Lathe: HPC Pressure

Mills: On the TSC pump.

Lathe: On the HPC pump.

 I/O PCB P39.21

Mills: Alarm 151 LOW THRU-SPINDLE COOLANT

Lathe: Alarm 8151 HPC LOW PRESSURE.
EC-1600: Y-axis temperature sensor. On the Y-axis column. I/O PCB P39.19 N/A
Lathe: X-axis temperature sensor.
 On the X-axis ballscrew ballnut.
 I/O PCB P2.14 N/A
Coolant Level
 On the coolant level float.
 I/O PCB P43.1 Low coolant Icon will apper when the coolant level is low.  The Low Coolant Concentrate icon will appear when machine is equipped with the Coolant Refill option.
Coolant Temperature On the coolant filter. I/O PCB P44.1 This temperature is for display purposes only and is shown on the gauge tab if the hardware is installed and enabled.
HPU Low Hydraulic Pressure On the hydraulic power unit. I/O PCB P48.7 Alarm 8134 LOW HYDRAULIC PRESSURE ON START
Note: UMC's that are equipped with Hydraulic Brakes for the B and C-axis can generate this alarm after a software upgrade if the hydraulic analog pressure sensor input is not mapped correctly.  Make sure the IO Configuration file has the correct mapping.
HPU Oil Temperature
 On the hydraulic power unit.
 I/O PCB P46.1

Alarm 2096 HPU OIL TEMPERATURE TOO HIGH
Spindle Temperature On the spindle head. I/O PCB P39.24 This temperature is for display purposes only and is shown on the gauge tab if the hardware is installed and enabled.
Spindle Motor Temperature
 On the spindle motor .
 I/O PCB P39.22 Alarm 254 SPINDLE MOTOR OVERHEAT
Analog Air Pressure
 On the air-lube cabinet.
 I/O PCB P34.5 Alarm 120 LOW AIR PRESSURE
Ambient Temperature On the base casting. I/O PCB P51.1 This temperature is for display purposes only and is shown on the gauge tab if the hardware is installed and enabled.
DC Voltage
 Inside the vector drive (the sensor is not serviceable).
 Maincon PCB J16 Alarm 160 LOW INCOMING LINE VOLTAGE
AC Line Voltage
 On the power-fail-detect-module (the sensor is not serviceable).
 Maincon PCB J3 Alarm 937 INPUT LINE POWER FAULT
Electronics Temperature

 On the Maincon PCB (the sensor is not serviceable).
 N/A Alarm 253 ELECTRONICS OVERHEAT