Case IH 1074 – CCM (Cab Control Module) or APH: Left external fender switch open circuit/short to GND

The controller is detecting an abnormal voltage from the left rear fender switch. The output signal does not fall within the expected range and is registering at less than 5% of the 8.5V reference voltage. This points to either a broken wire (open circuit), a wire rubbing against the chassis (short to ground), or an internal failure of the switch itself.

• MAXXUM T4E
• Case IH Farmall Series (40, 45, 50, 85C, 95C, 105C, 115U, 120A)
• Case IH Maxxum Series (Tier 3)
• Case IH Puma Series (130, 140, 145, 160)

1. 1

   Inspect the left external fender switch and its wiring pigtail for physical damage, moisture ingress, or heavy dirt accumulation.

2. 2

   Disconnect the switch and turn the key ON. Measure the reference voltage at the harness connector (should read approximately 8.5V).

3. 3

   Use a multimeter to check the signal wire between the switch connector and the CCM for continuity (to rule out an open circuit) and check for continuity to the tractor chassis (to rule out a short to ground).

4. 4

   Test the switch itself for proper resistance when actuated. If the switch reads open regardless of its position, it has failed internally.

1. 1

   Prepare tractor for service

   Turn off the tractor, lower all implements to the ground, and remove the key.

2. 2

   Locate switch

   Locate the left external fender switch on the rear left fender.

3. 3

   Disconnect harness

   Disconnect the wiring harness connector from the back of the switch.

4. 4

   Clean and inspect connector

   Clean the connector pins with electrical contact cleaner and inspect for bent pins or corrosion.

5. 5

   Repair wiring

   If the diagnostic checks revealed a wiring issue (short to ground or open circuit), trace the harness back to the cab and repair the damaged section of the wire.

6. 6

   Remove faulty switch

   If the wiring is intact and the 8.5V reference is present, the switch is faulty. Remove the retaining nut/clips holding the switch to the fender housing and pull the switch out.

7. 7

   Install replacement switch

   Install the replacement left external fender switch and secure it to the fender panel.

8. 8

   Reconnect harness

   Reconnect the wiring harness, ensuring the weather-tight seal clicks into place.

9. 9

   Test operation

   Turn the tractor on, clear the stored fault codes using the diagnostic display or electronic service tool, and test the remote fender switch to verify the PTO/hitch operates correctly.