New Holland 16121 – Air Conditioning Controller: Temperature Select Potentiometer Open or Shorted to Power

The fault code 16121 indicates an electrical issue with the temperature select potentiometer in the cab's climate control system. This component translates the temperature control knob's position into a voltage signal. An open circuit means the electrical connection is broken, while a short to power means the signal wire is incorrectly contacting a power source, causing an abnormally high voltage reading. When this occurs, the system may default to a preset temperature or disable the A/C compressor clutch, affecting air conditioning performance.

• T7.170
• T7.185
• T7.200
• T7.210
• T7.220
• T7.235
• T7.250
• T7.260
• T7.270
• T6.120
• T6.140
• T6.150
• T6.155
• T6.160
• T6.165
• T6.175
• T6.180
• T6010
• T6020
• T6030
• T6050
• T6070
• T6080
• T6090
• TSA Series
• T5040
• T5050
• T5060
• T5070
• TL70
• TL80
• TL90
• TL100
• TL80A
• TL90A
• TL100A

1. 1

   Visually inspect the temperature control knob for physical damage, cracks, or stripping that prevents it from turning the potentiometer shaft

2. 2

   Inspect the wiring harness and connectors leading to the HVAC control panel for damage, corrosion, or loose connections

3. 3

   Use the On-Board Diagnostics (H9 Menu) to monitor the temperature select potentiometer value while rotating the knob; the value should change smoothly without erratic jumps

4. 4

   Perform a multimeter resistance test on the potentiometer: check total resistance across the outer terminals, and perform a wiper test from the center to an outer terminal to ensure a smooth resistance sweep without dead spots

1. 1

   Confirm fault source

   Use the diagnostic H-menu or a multimeter to confirm whether the fault lies in the potentiometer circuit or just a physically broken knob.

2. 2

   Gain access to HVAC unit

   Carefully remove the necessary cab trim or dash panels to access the rear of the HVAC control unit.

3. 3

   Replace faulty component

   If the knob is stripped, pull the old knob off and replace it. If the potentiometer itself is faulty, replace the entire HVAC Control Unit, as the potentiometer is typically integral and not sold separately.

4. 4

   Install new components

   Connect the wiring harness to the new HVAC control unit and secure it in the dash, or press the new replacement knob firmly onto the aligned shaft.

5. 5

   Clear codes and verify

   Turn the ignition on, clear stored fault codes using the instrument cluster's diagnostic menu (HC menu) or Electronic Service Tool (EST), and operate the temperature control to verify the A/C system responds correctly.