Control Unit Harness Connector Checks

CAUTION: When removing or installing wiring harness connector to control unit, ignition switch must be in "OFF" position to prevent damage or injury.

Attach positive lead of voltmeter to battery positive post and negative voltmeter lead to battery negative terminal. Battery voltage should be at least 12 volts. Turn ignition switch "OFF" and disconnect harness connector from control unit. Connect voltmeter negative lead to a good ground and turn ignition switch back "ON".

Fig 1: Checking Voltage at Cavity No. 1
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Connect voltmeter positive lead to harness connector cavity No. 1. Reading should be within 1 volt of battery voltage. See Fig 1. If not, check and repair wiring and components illustrated by dark lines in Fig 2.
Now, connect positive voltmeter lead to harness connector cavity No. 2. Voltmeter reading should be within 1 volt of battery voltage. See Fig 3. If reading is not to specifications, check and repair wiring harness and components illustrated by dark lines in Fig 4.

Fig 2: Circuitry Checked if Cavity 1 Reading Is Not to Specifications
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Fig 3: Checking Voltage at Cavity No. 2
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Fig 4: Circuitry Checked if Cavity 2 Reading Is Not to Specifications
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If when checking wiring in previous step (dark lines in Fig 4), battery voltage exists at positive terminal of ignition coil, make primary and secondary coil resistance checks and check resistance of ballast resistor. See Fig 5. Remove wires from resistor and attach leads of an ohmmeter to each resistor terminal. Resistance should be 1.1-1.3 ohms. If reading is not to specifications, replace resistor.

Fig 5: Checking Ballast Resistor Resistance
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