Case IH 132 – ATC (Automatic Temperature Control) module: Low pressure switch (-) input shorted to power

This code indicates an electrical fault in the Air Conditioning (A/C) system. The Automatic Temperature Control (ATC) system monitors the A/C low-pressure switch, which protects the A/C compressor from running without adequate refrigerant. Code 132 is triggered when the controller detects that the negative (-) return circuit/input from the low-pressure switch is shorted to a 12V power source.

• STX Steiger
• Magnum MX215
• Magnum MX245
• Magnum MX275
• Magnum MX305
• Magnum 235-340 (Series 4)
• Steiger / STX Series (350-600 hp)

1. 1

   Inspect the wiring harness leading to the A/C low-pressure switch for rubbed, melted, or pinched wires causing a short to 12V.

2. 2

   Disconnect the harness from the switch and check for 12V on the negative (-) pin with the key ON to verify a harness short.

3. 3

   Test the low-pressure switch for internal shorts (should show continuity when system pressure is above 15-18 psi).

4. 4

   Hook up A/C manifold gauges to verify the system has the correct static refrigerant pressure.

1. 1

   Disconnect Power

   Turn off the tractor and disconnect the negative battery cable to prevent electrical spikes.

2. 2

   Repair Wiring

   If a short is found in the harness, trace the negative wire from the switch connector back to the ATC module. Locate the chafed or melted section where it is contacting a power source. Splice and solder the damaged wire, and protect it with heat-shrink tubing and wire loom.

3. 3

   Replace the Switch

   If internally shorted, locate the low-pressure switch threaded into the A/C suction line or receiver drier. Disconnect the electrical connector and unscrew the faulty switch (Note: Most modern Case IH low-pressure switches thread onto a Schrader valve fitting, meaning the switch can be unscrewed without discharging the A/C system. Verify this on your specific model before removing). Thread the new OEM switch onto the fitting and tighten to specification.

4. 4

   Reassemble and Clear Codes

   Reconnect the electrical harness and the battery. Start the tractor, turn on the A/C, and use the tractor's diagnostic display to clear the ATC 132 fault code. Verify that the A/C compressor clutch engages properly.