Modular Brush Assembly Replacement For Brush Block Assembly; Timer Test - Piper Navajo Chieftain PA-31-350 Service Manual

NAVAJO CHIEFTAIN SERVICE MANUAL
14-57. MODULAR
BRUSH
ASSEMBLY
REPLACEMENT
FOR BRUSH
BLOCK
ASSEMBLY. Modular brush assembly part number 3E2046-1 is a direct replacement for brush block
assembly 4E1350-5. Instructions concerning replacement of brush block assemblies with modular brush
assemblies are given in B. F. Goodrich Service Bulletin E-77-54.
14-58. MODULAR
BRUSH ASSEMBLY MAINTENANCE.
Brushes are not offered individually
as
replacements. When a brush wears out, the module containing it should be replaced as follows:
a. Remove the modular brush assembly from the aircraft by removing the attachment hardware.
and disconnect the wire harness.
b. Remove assembly screws and separate modules and spacers.
NOTE
The part number of each module is etched into the surface of the
plastic housing; replace with the same part number module.
c. Restack modules and spacers as shown in Figure 14-24. If there is interference between adjacent ring
terminals. reorient center module as shown in Figure 14-14.
NOTE
Ascertain
flat washer is positioned between star washer and
housing.
d.
Reconnect aircraft wire harness and insure adjacent ring terminals are not touchling.
e.
Install assembly on aircraft and check alignment.
14-59. TIMER TEST. Field experience indicates that too often the timer is considered at fault when the
true trouble lies elsewhere. Before removing a timer as defective, perform this test:
a. Disconnect wire harness at timer and with deicer switch ON, check voltage from Pin B of harness
plug to ground. If system voltage is not present, the fault is not in the timer. If system voltage is present at
Pin B, check ground circuit using ohmmeter from Pin G to ground. If no circuit is shown, the fault is in
ground lead, not in timer. If ground connection is open, the timer step switch will not change position.
b. When power and ground circuits have been checked, connect a jumper wire from Pin B of harness
to B contact of timer socket to power timer. Connect a jumper wire from Pin G of harness to G contact of
timer socket to complete the power circuit. Now use voltmeter from ground to the timer socket and check
that timer is cycling to deliver system voltage to C, D, E, and F contacts in that order. (The starting point is
not important but sequence must be as given.) Each of these four contacts must deliver voltage for
approximately 30 seconds, in turn, and there must be zero voltage on the three contacts not energized.
c. If the timer meets these requirements, it is not the cause of the trouble. If it fails to perform as
indicated, the trouble does lie in the timer and it should be replaced.
Reissued: 9/23/80
ACCESSORIES AND UTILITIES
4F10