Diagnostic Rf Sniffer - GMC G Service Manual

9-28 ACCESSORIES
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30. Low Vacuum Switch
31. To a Test Terminal
32. To The Brake Switch and Fuse Block
33. Filter Package. 1224205
34. 4-3 Shift (Momentary Open)
35. TCC Solenoid
36. 4th Gear Switch (Closed When Engaged)
37. Filter Ground Wire
38. 0.5 MFD Capacitor
39. 220 MFD Capacitor
Figure 35 — Torque Converter Lock Up Noise
ELECTRIC MOTOR NOISES (POWER WINDOWS,
BLOWER MOTORS)
Install a 0.5 MFD capacitor rated at 50 VDC across each
motor.
OTHER SWITCH POPS (BLOWER SWITCHES,
POWER LOCKS, POWER MIRRORS, PARK-NEUTRAL
SWITCH, POWER WINDOWS, WIPERS, REAR WIN­
DOW DEFOGGER)
Install a 0.5 MFD capacitor rated at 50 VDC across the
contacts of the switch, from the hot side of the switch to
ground or both.
31
!
grn
32
D
L01070

DIAGNOSTIC RF SNIFFER

The antenna sniffer can be used along with the vehicle's
radio to locate "Hot Spots" which are generating radio noise
interference. These "Hot Spots" will be found in the
harnesses, in the upper part of the dash or even between
the hood and windshield.
The sniffer is made from an old piece of antenna lead-in
from a mast or power antenna. The longer the lead-in the
better, since it will make the sniffer more flexible as a diag­
nostic tool.
Make the sniffer as shown in figure 36. The 50 mm (2
inch) section with the black coating and braided shield
stripped back becomes the antenna when the sniffer is
plugged into the radio's antenna socket. It can then be used
to probe and search out "Hot Spots."
Procedure:
1. While listening to the complaint noise, disconnect the
antenna and plug the sniffer into the antenna socket.
2. Turn the radio volume up.
3. When searching for the noise source, keep fingers off
of the probe, otherwise erroneous results will be
received.
When checking for noise on a wire, the best results will
be achieved when the sniffer is placed parallel to the wire.
It must be noted that the sniffer will also locate "normal"
hot spots. However, the technician who becomes familiar
with the sniffer's capabilities will find it the most useful diag­
nostic tool in noise suppression work.
40
c
\
40. Antenna Lead In
41. Center Wire
42. White Plastic Insulator
43. 50 mm (2 in.) of Coax Shield Removed
Figure 36 — RF Sniffer
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