Neutral Safety Switch: Testing and Inspection

DIAGNOSIS AND TESTING - CLUTCH INTERLOCK/UPSTOP SWITCH





The LHD clutch interlock/upstop switch is an assembly consisting of two switches: an engine starter inhibit switch (interlock) and a clutch pedal upstop switch (Fig. 9).





The RHD clutch interlock/upstop switch (Fig. 10) consists of a single, multi-function switch that is activated by the hydraulic clutch master cylinder push rod.

CLUTCH INTERLOCK SWITCH

Mechanical Test
1. With the park brake set and the transaxle IN NEUTRAL, turn the ignition key to the start position. The engine starter should not crank with the clutch pedal at rest (not depressed). If the starter cranks, proceed to the electrical test to determine whether the switch is defective or the circuit is shorted. If the vehicle does not crank, proceed to the next step.
2. With the park brake set and the transaxle IN NEUTRAL, fully depress the clutch pedal and turn the ignition key to the start position. The engine starter should crank. If the starter does not crank, visually inspect the clutch pedal for obstructions (floor mat, etc.). Make sure the clutch pedal lever contacts and fully closes the switch on LHD applications, and for proper installation of the master cylinder push rod/bushing on the pedal pin on RHD applications.

Electrical Test
1. Move ignition key to the "OFF/LOCK" position and remove key
2. Set park brake.
3. Disconnect the clutch interlock/upstop switch connector.





4. Using an ohmmeter, check for continuity between terminals 2 & 3 (Fig. 11) with the interlock switch not depressed (clutch pedal at rest). There should be no continuity between the terminals (open circuit).
5. LHD Models: Fully depress the clutch pedal to close the switch. The switch button should compress at least 1.25 mm (0.050 inch) on LHD applications. The ohmmeter should show continuity (0 ohms resistance). RHD Models: Disconnect the push rod from the pedal pin and actuate the push rod by hand to close the switch. The ohmmeter should show continuity (0 ohms). Inspect the plastic push rod retainer for damage. If it is damaged (broken/cracked) it MUST be replaced before reinstalling the push rod to the pedal.
6. If ohmmeter readings do not fall within these ranges, the switch assembly, or the pedal bracket assembly, is defective and should be replaced. If the switch tests ok, wiring is defective.

UPSTOP SWITCH

Mechanical Test
1. Raise vehicle on hoist.
2. Start engine and operate speed control to maintain speed.
3. Depress clutch pedal at least 33 mm (1.30 inch). Speed control operation should terminate. If speed control does not terminate, the upstop switch is defective or the related wiring is shorted. Proceed to the upstop switch electrical test.

Electrical Test
1. Move ignition key to the "OFF/LOCK" position and remove key
2. Set park brake.
3. Disconnect the clutch interlock/upstop switch connector.
4. Using an ohmmeter, check for continuity between terminals 1 & 2 (Fig. 11) with the upstop switch depressed (clutch pedal at rest). The ohmmeter should show continuity (0 ohms).
5. Depress the clutch pedal at least 33 mm (1.30 inch) check for continuity between terminals 1 & 2. There should be no continuity between the terminals (open circuit).
6. If ohmmeter readings do not fall within these ranges, the switch assembly is defective and should be replaced. If the switch tests ok, wiring is defective.





SERVICE DIAGNOSIS - CLUTCH INTERLOCK/UPSTOP SWITCH