SYMPTOM RELATED DIAGNOSTICS

SWITCH CIRCUIT FAILURE (continued)

Test 4

Checking for stray voltage at the module

1.Turn the ignition key to the ON position.

2.With the switch OFF, measure the voltage from the pin at the V-MAC II module connector to a good ground.

If the voltage is greater than 0.5 volts, proceed to Test 9.

If the voltage is less than 0.5 volts, proceed to Test 8.

Test 8

Checking switch voltage at the module

1.With the switch ON, measure the voltage from the pin at the V-MAC II module connector to a good ground.

If the voltage is greater than 10 volts, replace the V-MAC II module. Retest to be sure the problem has been corrected.

If the voltage is less than 10 volts, proceed to Test 17.

Test 9

Checking for a short to voltage in the harness

1.Turn the ignition key to the OFF position.

2.Disconnect the wire supplying 12 volts to the switch at the switch terminal.

3.Turn the ignition key to the ON position.

4.Measure the voltage from the V-MAC II module connector pin to a good ground.

If 12 volts are present, proceed to Test 19.

If 12 volts are not present, examine the switch for bent or damaged pins that would cause a short to voltage. Repair the pins or replace the switch. Retest to be sure the problem has been corrected.

Test 17

Checking for voltage to the switch

1.Turn the ignition key to the OFF position.

2.Disconnect the wire leading from the switch terminal to the V-MAC II module at the switch terminal.

3.Turn the ignition key to the ON position.

4.Measure the voltage at the switch voltage supply terminal to a good ground.

If 12 volts are present, proceed to Test 34.

If 12 volts are not present, there is a loss of power to the switch. Locate and repair the problem. Retest to be sure the problem has been corrected.

Test 19

Checking for a short in the harness

1.Turn the ignition key to the OFF position.

2.Disconnect the remaining V-MAC II module connectors.

3.Check for continuity between the switch signal pin and each of the other pins (one at a time) on the J1A, J1B and J2 connectors.

If there is continuity with another pin, locate and repair the short in the harness. Retest to be sure the problem has been corrected.

If there is no continuity, there is a short to voltage somewhere else in the cab or dashboard, between the switch and the V-MAC II module. Locate and repair the short to voltage. Retest to be sure the problem has been corrected.