924 & 944 Series
- Disconnect harness plugs at control unit. Control unit is located in driver's footwell, behind center console. Following tests should be made at harness plugs. Plug No. 1 is from switch control. Plug No. 2 goes to servo unit. Plug No. 2 is identified by lack of No. 3 terminal pin. See Figure .
- Check plug No. 1 with voltmeter. Turn ignition on. Terminal No. 4 should have battery voltage. Terminal No. 8 is a permanent ground. Use it to test plug terminals.
- Battery voltage should be present at terminal No. 2 when brake pedal is depressed. If not, check brake switch. Check terminal No. 3 for battery voltage. When control switch is slid inward to off, zero voltage should be present.
- Check terminal No. 5 for battery voltage when push button switch is pushed. Check terminal no. 6 for voltage when sliding switch is moved outward to "ON/SET" position.
- Connect tester between terminals No. 4 and 7. Battery voltage should be present until clutch is depressed and circuit is opened. If above circuits do not meet testing specifications, repair or replace switches and wiring as necessary. If defective control unit is suspected, test by substitution.
- Connect tester between battery positive and terminal No. 1. With ignition off, voltage should be one volt or less than battery voltage. With ignition on, zero voltage should be present. Operate vehicle at 30 MPH. Voltage should be approximately 4 volts. Ensure voltage increases with vehicle speed.
- Using an ohmmeter, check the following circuits of plug No. 2. Resistance between terminals No. 1 and 2 should be 30-40 ohms.
- Resistance between terminals No. 4 and 7 should be 2-4 ohms. Resistance between terminals No. 4 and 8 should be 2-4 ohms.
- Resistance between terminals No. 5 and 6 should be 20-40 ohms. If servo unit resistance in not within specifications and unit is suspect, test by substitution.