My 2004 Dodge Ram 2500 SLT Diesel vent control
Hi!!
IT SEEMS LIKE YOU HAVE A SHORT IN THE HEATING GRID, EITHER THE MIRRORS OR THE BACK WINDOW.
READ THE FOLLOWING INFO. AND PERFORM THE TESTS TO PINPOINT THE FAULT.
OUTSIDE MIRROR HEATING GRID
Vehicles equipped with the optional heated mirror
system have an electric heating grid located behind
the mirror glass of each outside rear view mirror.
The heated mirrors are controlled by the rear window
defogger switch. Electrical current is directed to
the heating grid inside the mirror only when the rear
window defogger switch is in the On position.
The heating grid behind each outside mirror glass
cannot be repaired and, if faulty or damaged, the
entire power mirror unit must be replaced.
DEFOGGER SWITCH
The rear window defogger switch is integral to the
rear window switch pod, which includes the rear
wiper and washer switches. The rear window switch
pod is installed in the instrument panel lower bezel,
which is located near the center of the lower instrument
panel, below the heater and air conditioner controls.
The rear window switch pod also contains the rear
window defogger logic and timer circuitry, an amber
defogger indicator lamp, the rear window defogger
relay, and two switch illumination lamps. The indicator
and illumination lamps in the switch pod use
incandescent bulbs, which can be serviced.
The momentary-type rear window defogger switch
provides a hard wired ground signal to the rear window
defogger logic and timer circuitry, each time it is
depressed. The rear window defogger timer and logic
circuitry responds by energizing or de-energizing the
rear window defogger relay and the amber defogger
indicator lamp, which lights to indicate when the
defogger system is turned On. Energizing the rear
window defogger relay provides electrical current to
the rear window defogger grid.
The rear window switch pod cannot be repaired. If
any function of the switch pod except lighting is
faulty or damaged, the entire switch pod must be
replaced.
Turn the ignition switch to the On position. Set
the defogger switch in the On position. The rear window
defogger operation can be checked by feeling the
rear window or outside rear view mirror glass. A distinct
difference in temperature between the grid lines
and the adjacent clear glass or the mirror glass can
be detected within three to four minutes of operation.
Using a 12-volt DC voltmeter, contact the rear
glass heating grid terminal A (right side) with the
negative lead, and terminal B (left side) with the positive
lead (Fig. 1). The voltmeter should read battery
voltage.
The above checks will confirm system operation.
Illumination of the defogger switch indicator lamp
means that there is electrical current available at the
output of the rear window defogger logic and timer
circuitry, but does not confirm that the electrical current
is reaching the rear glass heating grid lines.
If the defogger system does not operate, the problem
should be isolated in the following manner:
(1) Confirm that the ignition switch is in the On
position.
(2) Ensure that the rear glass heating grid feed
and ground wires are connected to the glass. Confirm
that the ground wire has continuity to ground.
(3) Check the fuses in the Power Distribution Center
(PDC) and in the junction block. The fuses must
be tight in their receptacles and all electrical connections
must be secure.
When the above steps have been completed and the
rear glass heating grid is still inoperative, one or
more of the following is faulty:
Rear window switch pod
Rear window grid lines (all grid lines would
have to be broken or one of the feed wires disconnected
for the entire system to be inoperative).
If setting the defogger switch to the On position
produces a severe voltmeter deflection, check for a
short circuit between the rear window switch pod
defogger relay output and the rear glass heating grid.