mxu 400 Manuel atelier : Page 93

                                                                      4. When the brake pedal is depressed, the meter must
                                                               show less than 1 ohm.
       Brakelight Switch
                  (Pressure)                                 NOTE: If the meter shows more than 1 ohm of
                                                           resistance, replace the switch.


The brakelight switch is located on the top of the aux-
iliary brake master cylinder and is pressure activated       Oil Temperature and
by the hand brake or the auxiliary brake pedal. This
switch also activates the start-in-gear (SIG) relay in       Cooling Fan Switches
the power distribution module (PDM).
 NOTE: The ignition switch must be in the ON
                                                            1. Connect the meter leads (selector in the OHMS
position.                                                      position) to the switch contacts.
VOLTAGE                                                     2. Suspend the switch and a thermometer in a con-
(Wiring Harness Side)                                          tainer of cooking oil; then heat the oil.

 1. Set the meter selector to the DC Voltage position.       NOTE: Neither the switch nor the thermometer
                                                           should be allowed to touch the bottom of the con-
 2. Connect the red tester to the brown/black wire;        tainer or inaccurate readings will occur. Use wire
    then connect the black tester lead to ground.          holders to suspend switch and thermometer.
 3. The meter must show battery voltage.
                                                                           ! WARNING
  NOTE: If the meter shows no battery voltage,             Wear insulated gloves and safety glasses. Heated oil
troubleshoot the battery, fuse, switch, or the main        can cause severe burns.
wiring harness.

 NOTE: If the meter shows battery voltage, the

                                                                                                                     5
main wiring harness is good; proceed to test the
switch/component or connector.

RESISTANCE (Switch)

                 ! CAUTION
Always disconnect the battery when performing
resistance tests to avoid damaging the multimeter.

 1. Remove the spade connectors from the brake
    switch.                                                                                               733-554C

 2. Set the meter selector to the OHMS position.            3. On the oil temperature switch when the oil temper-
                                                               ature reaches 160° C (320° F), the meter should
 3. Connect the red tester lead to one switch terminal;        read a closed circuit.
    then connect the black tester lead to the other
    switch terminal.                                        4. On the oil temperature switch, allow the oil to
                                                               cool, and when the temperature is at (or just
                                                               before) a temperature of 140° C (284° F), the
                                                               meter should read an open circuit.
                                                            5. On the cooling fan switch when the temperature
                                                               reaches 120° C (248° F), the meter should read a
                                                               closed circuit.
                                                            6. On the cooling fan switch, allow the oil to cool,
                                                               and when the temperature is at (or just before) a
                                                               temperature of 110° C (230° F), the meter should
                                                               read an open circuit.
                                                            7. If the readings are not as indicated, the switch
                                                               must be replaced.
                                                   KC274




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