ELECT-17, Ignition Switch and Wiring Test


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Introduction

Bad ignition switches are becoming a more common cause of starting problems on 944s. So, take a look at your ignition switch and if it's cracked, it's likely the source of your problem This procedure is used for testing purposes to determine the condition of the cranking portion of the ignition switch and the wiring from the ignition switch to the starter.

Tools

Testing Procedure

  1. Disconnect the battery positive lead.
  2. Disconnect the electrical plug from the ignition switch.
  3. Check the operation of the cranking contacts on the ignition switch as follows:
    1. Connect an ohmmeter between Terminals 30 and 50 on the ignition switch. If you are unsure which terminals those are, look at the electrical connector for the wires that attach to the ignition switch. If the wires were still connected to the ignition switch, Terminal 30 would be connected to the large diameter Red Wire and Terminal 50 would be connected to the large diameter Red Wire with Black Stripe.
    2. Turn the ignition switch to the start position as if cranking the engine and read the resistance.
    3. The resistance should go from and infinite resistance to approximately 0 ohms when the switch is turned.
    4. If the correct resistance is not obtained the ignition switch is bad and should be replaced.
  4. If the ignition switch checks okay, check the ignition wiring as follows:
    1. Disconnect the wire from the switch terminal on the starter solenoid (bendix).
    2. Make up a jumper to reach from the starter to the ignition switch.
    3. Attach the jumper from the switch lead at the starter solenoid (Red Wire/Black Stripe) to the Terminal on the ignition switch electrical connector with the Red Wire/Black Stripe.
    4. Check the wire resistance with and ohmmeter. It should be approximately 0 ohms (less than 5 ohms). If not, the wire is broken and should be replaced.

    Clark's Garage 1998