Service Home Analog Sensors - Troubleshooting Guide - CHC - TG0026
Last updated: 01/27/2026

Analog Sensors - Troubleshooting Guide - CHC

TG0026

Analog Input Troubleshooting

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/Mocon 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 / Mocon PCB.

CHC - Analog Sensor Information

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.

 Maincon / Mocon P15

Mills: Alarm 151 LOW THRU-SPINDLE COOLANT

Lathe: Alarm 151 HPC LOW PRESSURE.
AC Voltage
 Inside the vector drive (the sensor is not serviceable).
 Maincon / Mocon P17 Alarm 160 LOW INCOMING LINE VOLTAGE
HPU Low Hydraulic Pressure
 On the hydraulic power unit.
 Maincon / Mocon P19
 Alarm 134 LOW HYDRAULIC PRESSURE
Lathe: X-axis temperature sensor.
 On the X-axis ballscrew ballnut.
 Maincon / Mocon P21 N/A
Coolant Level
 On the coolant level float.
 Maincon / Mocon P22
 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.
AC Line Voltage
 On the power-fail-detect-module (the sensor is not serviceable).
 Maincon / Mocon P26
 Alarm 937 INPUT LINE POWER FAULT

Horizontal: Y-axis temperature sensor.

Lathe: HPU Pressure

Horizontal: On the Y-axis column.

Lathe: On the hydraulic power unit.

 Maincon / Mocon P27

Horizontal: N/A

Lathe: Alarm 2091 HPU OIL TEMPERATURE TOO HIGH
Spindle Motor Temperature
 On the spindle motor .
 Maincon / Mocon P28
 Alarm 254 SPINDLE MOTOR OVERHEAT
Air Pressure
 On the air-lube cabinet
 Maincon / Mocon P37
 Alarm 120 LOW AIR PRESSURE
Electronics Temperature

 On the Maincon / Mocon (the sensor is not serviceable).
 -
 Alarm 253 ELECTRONICS OVERHEAT