Figure 18-2. Radio Interference Suppression Filters and Cable Shielding
shielding boxes provided with a means of attachment to
between the filter and firewall is kept as short as
the conduit and shielding containing the connecting
possible. In later production vehicles, this filter is
replaced by a capacitor that usually is mounted on or
near the coil, with its lead connected to the switch side of
the ignition coil primary circuit.
18-6. Typical Applications of Suppression Systems
(4) Filters are used in regulator circuits. One
usually is connected between the battery terminal of the
Transport Vehicles - Ordinary Suppression
regulator and the ammeter, one is connected in the
System. The system found on most vehicles consists of
generator armature lead, and one sometimes is
the items described below.
connected in the field lead between the generator and
regulator. These filters are mounted on the firewall in
(1) Resistor-suppressors are used in each
such a position that the exposed leads leaving the filter
high-tension lead from distributor to spark plugs. The
are as short as possible. On certain vehicles, capacitors
suppressors are usually of a type that will slip over the
(usually 0.1-microfarad capacitance) may be found at
terminal of the plug. The lead is screwed directly into the
these points, mounted on the firewall, with the leads
suppressor, thus locating the suppressor as close as
connected to the battery and generator armature
possible to the spark gap in the plug.
terminals. A 0.01-microfarad capacitor sometimes is
applied with its lead connected to the field terminal of the
(2) A resistor-suppresssor is used in the high-
tension lead from distributor to coil. This suppressor is
placed in the lead as close as possible to the distributor.
(5) A capacitor is mounted on the generator
Usually, it will be found approximately 1 or 2 inches away
with its lead connected to the output terminal. Capacitors
from the distributor.
are used on certain lighting circuits, either mounted on
the firewall or close to any junction point. The lead is
(3) A filter is placed in the lead from the ignition
connected to the circuit that may be carrying radio
coil to the ignition switch. This filter is mounted on the
firewall, where the lead goes through to the switch.
Thus, the exposed lead