Ignition Switch and Wiring Test
Ohmmeter-based procedure for testing the cranking contacts of the 944 ignition switch and the wiring from the switch to the starter solenoid, used to isolate no-crank conditions.
Introduction
Cracked ignition switches are a known cause of starting problems on 944s. Visually inspect the ignition switch; a cracked housing is a strong indicator that the switch is the source of the problem. This procedure tests the cranking contacts of the ignition switch and the wiring from the switch to the starter solenoid.
Tools
- Wire jumpers
- Multimeter (ohmmeter function)
Testing Procedure
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Disconnect the battery positive lead.
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Disconnect the electrical plug from the ignition switch.
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Test the cranking contacts on the ignition switch:
a. Connect an ohmmeter between Terminals 30 and 50 on the ignition switch. Terminal 30 corresponds to the large-diameter red wire, and Terminal 50 corresponds to the large-diameter red wire with a black stripe, as they appear on the electrical connector. b. Turn the ignition switch to the Start position as if cranking the engine. c. Resistance should drop from infinite (open) to approximately 0 Ω when the switch is turned. If the correct resistance is not obtained, the ignition switch is bad and must be replaced.
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If the ignition switch tests good, check the ignition wiring:
a. Disconnect the wire from the switch terminal on the starter solenoid. b. Make up a jumper long enough to reach from the starter to the ignition switch connector. c. Attach the jumper from the switch lead at the starter solenoid (red wire with black stripe) to the corresponding terminal on the ignition switch electrical connector (also red wire with black stripe). d. Measure wire resistance with the ohmmeter. It should read approximately 0 Ω (less than 5 Ω). A higher reading indicates a broken wire that must be replaced.