Ignition Switch and Wiring Test

Overview

This guide helps you test the ignition switch and its wiring on your Porsche 944 S / S2 with the 16v engine. A faulty ignition switch is a common reason for starting issues. By checking the switch and the wiring to the starter, you can pinpoint if the switch is cracked or if there’s a wiring problem, ensuring your car starts reliably.

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Tools Required

• Wire jumpers
• Multimeter
• 10mm (3/8 inch) wrench (for battery terminal)

Step-by-Step Procedure

Step 1: Disconnect the Battery

1. Use a 10mm (3/8 inch) wrench to loosen and disconnect the positive battery lead from the battery terminal. This keeps you safe while working with electrical components.

Step 2: Access the Ignition Switch

2. Locate the ignition switch behind the steering wheel and disconnect its electrical plug. This plug connects the switch to the car’s wiring.

Step 3: Test the Ignition Switch

3. Take your multimeter and set it to measure resistance (ohms).
4. Connect the multimeter probes to Terminals 30 and 50 on the ignition switch plug. Terminal 30 is where the large red wire connects, and Terminal 50 is where the large red wire with a black stripe connects.
5. Turn the ignition key to the “start” position, as if you’re cranking the engine.
6. Check the multimeter reading. The resistance should drop from infinite (no connection) to about 0 ohms (full connection) when the key is turned.
7. If the resistance doesn’t drop to near 0 ohms, the ignition switch is faulty and needs replacing. For the Porsche 944 S / S2, use ignition switch 944 610 911 00.

Step 4: Test the Wiring to the Starter

8. If the ignition switch tests okay, move to the starter. Find the starter solenoid under the car, near the engine and transmission.
9. Disconnect the wire from the switch terminal on the starter solenoid (this is the red wire with a black stripe).
10. Make a jumper wire long enough to reach from the starter to the ignition switch location.
11. Attach one end of the jumper to the red wire with a black stripe at the starter solenoid.
12. Attach the other end to Terminal 50 on the ignition switch plug (the spot for the red wire with a black stripe).
13. Use the multimeter to measure resistance between the two ends of the wire. It should be about 0 ohms (less than 5 ohms is acceptable).
14. If the resistance is higher than 5 ohms, the wire is damaged and should be replaced with a new red/black stripe wire, 944 607 015 00.

Post Procedure Checklist

• Reconnect the battery positive lead and tighten it to 10 Nm (7 ft-lbs) using a 10mm (3/8 inch) wrench.
• Turn the key to the “start” position and listen for the starter to engage smoothly.
• Ensure the car starts without hesitation.
• Check all connections for security and no exposed wires.

Sources

• Clark’s Garage
• Pelican Parts
• Porsche 944 Workshop Manual, Volume 1
• Youtube