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8N - 2
REAR WINDOW DEFOGGER
•
t h a t there is power available a t the o u t p u t o f t h e r e -
lay only, a n d does n o t necessarily verify system op-
e r a t i o n .
I f the rear window defogger does not operate, t h e
p r o b l e m should be isolated i n t h e following manner:
(1) C o n f i r m t h a t i g n i t i o n switch is O N .
(2) Ensure t h a t t h e heated rear window feed w i r e
is connected to t h e t e r m i n a l or p i g t a i l a n d t h a t t h e
g r o u n d w i r e is i n fact grounded.
(3) Ensure t h a t the fuse is operational a n d a l l elec-
t r i c a l connections are secure.
W h e n the above steps have been completed and t h e
system is s t i l l inoperative, one or more of the follow-
i n g is defective:
(a) Control switch/timer relay module.
(b) Rear window g r i d lines (all g r i d lines w o u l d
have to be broken) or one of the feed wires are n o t
connected for the system to be inoperative.
The following paragraphs outline component
check-out procedures.
I f t u r n i n g t h e switch O N produces severe volt-
meter
deflection,
t h e circuit
should be closely
checked for a s h o r t i n g condition.
I f system operation has been verified b u t i n d i -
cator b u l b does n o t l i g h t , check and replace bulb.
For detailed w i r i n g information, refer t o Group
8 W - W i r i n g Diagrams.
REAR WINDOW GRID LINES TEST
The horizontal g r i d lines and vertical bus b a r lines
p r i n t e d a n d baked on inside surface of rear w i n d o w
glass (Fig. 1) comprise an electrical p a r a l l e l circuit.
The electrically conductive lines are composed o f a
silver-ceramic m a t e r i a l w h i c h when baked o n glass
becomes bonded to t h e glass and is h i g h l y resistant
to abrasion. I t is possible, however, t h a t a break may
exist or occur i n a n i n d i v i d u a l g r i d line r e s u l t i n g i n
no current flow t h r o u g h the line. To detect breaks i n
g r i d lines, t h e following procedure is required:
(1) T u r n i g n i t i o n on and push control switch to O N .
T h e indicator l i g h t should come on.
(2) U s i n g a DC voltmeter w i t h 0-15 volt range, con-
t a c t vertical bus b a r connecting g r i d lines o n passen-
ger side of vehicle (point A of Fig. 1) w i t h
negative
lead of voltmeter. W i t h positive lead of voltmeter,
contact vertical bus bar on driver side o f vehicle
(point B of Fig. 1). The voltmeter should read 10-14
volts.
(3) W i t h negative lead of voltmeter, contact a good
body ground point. The voltage reading should n o t
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 g r i d line a t
M i d - P o i n t w i t h positive lead. A reading o f approxi-
m a t e l y 6 volts indicates a line is good. A r e a d i n g of 0
volts indicates a break i n line between M i d - P o i n t C
and Point B . A reading o f 10-14 volts indicates a
break between Mid-Point C a n d g r o u n d Point A .
Move t o w a r d break and voltage w i l l change as soon
as break is crossed.
CONTROL SWITCH/TIMER MODULE TEST
Control switch/timer relay module m a y be tested
in-vehicle or bench tested. I n vehicle t e s t i n g i s ac-
complished i n t h e following m a n n e r :
(1) Remove t h e switch from t h e i n s t r u m e n t panel
(refer to Control Switch Replacement) a n d leave t h e
switch connector, plugged i n .
(2) T u r n i g n i t i o n O N .
(3) U s i n g a D C voltmeter w i t h 0-15 range, check
voltage a t t e r m i n a l s B , I and L (Figs. 2 and 3). Ter-
minals B and I should confirm a voltage o f 10 t o 14
volts to ground. T e r m i n a l L should c o n f i r m 0 volts to
ground. W h e n t e r m i n a l s B a n d I show n o voltage,
trace circuit upstream o f switch/relay module for
problem ( w i r i n g cut, fusible l i n k o r c i r c u i t breaker
inoperative, b u l k h e a d connector n o t operative, etc.).
I f t e r m i n a l L indicates voltage, place s w i t c h i n O F F
position. I f voltage a t L is s t i l l i n d i c a t e d or indicator
lamp remains on, t h e switch/relay module should be
replaced.
P - T - I F U S E
# 1 4
r - T - i
4
3 A M P
* )
F U S E # 1 3
2 0 A M P
BATTERY
HEATED REAR
WINDOW DEFOGGER
SWITCH
(INSTRUMENT PANEL)
18 GAUGE
FUSIBLE
LINK
ON/OFF
REAR WINDOW GRID LINE STRUCTURE
Fig. 2 Systems Electrical Circuit
1
J908N-9
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