Timer Test; Other Components - Piper PA-31-350 Maintenance Manual

PIPER AIRCRAFT
T-1020
MAINTENANCE MANUAL
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:
1. 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.
2. 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.
3. If the timer meets these requirments, 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.
OTHER COMPONENTS.
Do not attempt internal repairs of the timer, ammeter, or switch. If inoperative, these components must
be replaced with one of the correct part numbers. For any other repair or maintenance problems not covered in
this manual, inquire at Aerospace and Defense Products Division of the B. F. Goodrich Company. Akron.
Ohio 44318.
402
GRAY PLASTIC BONDED TO
SHINY SIDE OF DEICER
STRAP IN THIS AREA
PROP DEICER
DEICER
LEAD STRAP
Figure 30-22. Propeller Blade Low Pitch Position
30-64-00
Page 30-47
Issued: September 2, 1981
3D3