fog light bulb DODGE TRUCK 1993 Service Repair Manual

8N
- 2
REAR WINDOW DEFOGGER

• (b) Rear window grid lines (all grid lines would
have to be broken) or one of the feed wires are not
connected for the system to be inoperative.
The following paragraphs outline component check­
out procedures.
If turning the switch ON produces severe voltmeter
deflection, the circuit should be closely checked for a shorting condition. If system operation has been verified but indicator
bulb does not light, check and replace bulb.
For detailed wiring information, refer to Group 8W
- Wiring Diagrams.

REAR
WINDOW GRID LINES TEST
Horizontal grid lines and vertical bus bar lines
printed and baked on inside surface of rear window glass (Fig. 1) comprise an electrical parallel circuit.
The electrically conductive lines are made of a silver- ceramic material. When baked onto glass they be­
come bonded to the glass and are highly resistant to abrasion. It is possible, however, that a break may
exist or occur in an individual grid line resulting in
no current flow through the line. To detect breaks in
grid lines, the following procedure is required: (1) Turn ignition on and push control switch to
ON. Indicator light should come on. (2) Contact negative lead of a DC voltmeter, to
vertical bus bar connecting grid lines on passenger side of vehicle (point A of Fig. 1). Contact positive
lead of voltmeter, to vertical bus bar on driver side of
vehicle (point B of Fig. 1). Voltmeter should read 10-14 volts. (3) With negative lead of voltmeter, contact a good
body ground point. Voltage reading should not change. A different reading indicates a poor ground connection. (4) Connect negative lead of voltmeter to Point A
on passenger side bus bar and touch each grid line at
Mid-Point with positive lead. A reading of approxi­ mately 6 volts indicates a line is good. A reading of 0
volts indicates a break in line between Mid-Point C and Point B. A reading of 10-14 volts indicates a
break between Mid-Point C and ground Point A. Move toward break and voltage will change as soon as break is crossed.

CONTROL SWITCH/TIMER MODULE TEST
Control switch/timer relay module may be tested
in-vehicle or bench tested. In vehicle testing is ac­
complished in the following manner: (1) Remove switch from instrument panel (refer to
Control Switch Replacement) and leave switch con­
nector plugged in. (2) Turn ignition ON.
(3) Using a DC voltmeter, check voltage at termi­ nals B, I and L (Figs. 2 and 3). Terminals B and I
should confirm a voltage of 10 to 14 volts to ground.
Terminal L should confirm 0 volts to ground. When terminals B and I show no voltage, trace circuit up­
stream of switch/relay module for cause:
• wiring cut
• fusible link faulty
• circuit breaker inoperative
• bulkhead connection bad, etc. If terminal L indicates voltage, place switch in
OFF position. If voltage at L is still indicated or in­
dicator lamp remains on, switch/relay module should
be replaced.
"XI
FUSE
#14
rr~
P 3
AAAP
P
FUSE
#3
20
AAAP
BATTERY

HEATED
REAR

WINDOW
DEFOGGER
SWITCH

(INSTRUMENT
PANEL)

ON/OFF
ILLUMINATION
LAMP

fez TIMER
L.E.I
INDICATOR
LIGHT
-©-
18
GAUGE

FUSIBLE
LINK

IGNITION POWER
MIDPOINT
"C"

CONNECTOR (TYPICAL)
POINT
"A"
POINT
"B"
GROUND
CONNECTOR

REAR
WINDOW
GRID
LINE
STRUCTURE
Fig.
2
Systems
Electrical Circuit
J928N-5

(4) If the relay checks out to this point, momen­
tarily operate switch to ON position. The indicator lamp should come on and remain on for approxi­
mately 10 minutes. Terminal L should confirm volt­
age.
If the indicator lamp fails to light or voltage at
terminal L is not confirmed the switch/relay module should be replaced.
Bench checking of the relay may be accomplished
in the following manner. By following the in-vehicle
procedure except Step 2: With a DC power supply, apply 12 volts to terminal B and I and ground termi­
nal G.