MAINTENANCE OF THE M88A1 - OD1672 - LESSON 3/TASK 2
Step 2. To fault isolate the ventilator blower system for a defective VENT
BLOWER switch (figure 40, view B, on page 89) requires the use of the
ventilator blower electrical diagram and test equipment. This procedure is
provided in the following substeps and is based on the use of the ventilator
blower electrical diagram (figure 43 on the following page) and a
(a) Disconnect the accessories panel plug and, with the voltmeter,
measure the voltage from the panel plug pin A to a suitable vehicle ground.
The voltmeter should read 24 vdc.
(b) Since the voltmeter reads 24 vdc, close the VENT BLOWER switch and
receptacle pins A and B. The ohmmeter should read zero.
(c) The ohmmeter does not read zero, but instead reads infinity. This
is an indication that there is an open circuit somewhere between pin A and
pin B in the accessories panel circuit of the ventilator blower. Disconnect
the plugs from the VENT BLOWER switch and measure the resistance across the
VENT BLOWER switch receptacles. The ohmmeter should read zero Ohms.
(d) Since the ohmmeter does not read zero Ohms, but reads infinity, this
reveals that the VENT BLOWER switch is defective and needs to be replaced.
In the process of checking the VENT BLOWER switch on the accessories panel,
it is noticed that the insulation on one of the female wire connectors is
damaged and must be repaired, and that the connection itself is damaged and
must be replaced.
The following paragraph provides the procedure for the
replacement of the VENT BLOWER switch and the repair of the damaged female
Maintenance and Repair of the Ventilator Blower System. The following
subparagraphs provide the procedures for the removal of the defective VENT
BLOWER switch and installation of a new switch, and the repair of damage on
a female connector.
(1) Removal of the VENT BLOWER Switch.
Step 1. Turn the vehicle MASTER switch (refer back to figure 28, view C, on
page 67) to the OFF