clayton3854

few questions as im new to the zj scene, typically an xj guy. for the overdrive switch, what mph should i engage at? i figure highway speeds but i know small suv's engage the overdrive switch as low as 45. also on my overhead console when it shows the direction im going (n/s/w/e) it says OC next to the direction? what does OC stand for and isnt it supposed to show the temp there? for now that is it, as i drive the zj more and get more used to it im sure ill have more questions. thanks everyone

-Ethan

timberwolf

it should be the outside temp next to the compass
was the console set to celsius instead of fahrenheit?

the overdrive is normally engaged unless you turn it off, usually for towing or climbing

clayton3854

i have no idea, when i first got the jeep the outside temp gauge worked then after working on it for a few months n it sitting in my yard now that its on the road it just says OC

so your saying i should just leave the overdrive on? that i dont needa turn it off.

Willys55

OC out of calibration.

Bustedback

Leave the overdrive on unless you're towing.

ol"blue

Leave overdrive engaged unless towing or in hilly terrain, as stated above. It kicks in around 46 MPH.
As for the thermometer/compass, this info comes from the ZJ FSM:

THERMOMETER
The thermometer function is supported by a ambient
temperature sensor, a wiring circuit, the Body
Control Module (BCM), the CCD data bus, and a portion
of the overhead console trip computer, compass,
and thermometer display module display. The sensor
is mounted outside the passenger compartment near
the front and center of the vehicle.
If any portion of the ambient temperature sensor
circuit fails, the thermometer display will self-diagnose
the circuit. An “SC” (short circuit) will appear in
the display in place of the temperature, when the
sensor is exposed to temperatures above 55° C (131°
F), or if the sensor circuit is shorted. An “OC” (open
circuit) will appear in the display in place of the temperature,
when the sensor is exposed to temperatures
below -40° C (-40° F), or if the sensor circuit is open.
The ambient temperature sensor circuit can also be
diagnosed using the following Sensor Test, and Sensor
Circuit Test. If the temperature sensor and circuit
are confirmed to be OK, but the temperature
display is inoperative or incorrect, see the Trip Computer,
Compass, and Thermometer Display Module
diagnosis in this group. For circuit descriptions and
diagrams, refer to 8W-45 - Body Control Module and
8W-49 - Overhead Console in Group 8W - Wiring
Diagrams.

SENSOR TEST
(1) Turn the ignition switch to the Off position.
Unplug the temperature sensor wire harness connector.
(2) Measure the resistance of the temperature sensor.
At -40° C (-40° F), the sensor resistance is 336
kilohms. At 55° C (140° F), the sensor resistance is
2.488 kilohms. The sensor resistance should read
between these two values. If OK, go to the Sensor
Circuit Test. If not OK, replace the faulty sensor.

SENSOR CIRCUIT TEST
(1) Turn the ignition switch to the Off position.
Disconnect and isolate the battery negative cable.
Unplug the ambient temperature sensor wire harness
connector and the black 24-way Body Control
Module (BCM) wire harness connector.
(2) Connect a jumper wire between the two terminals
in the body half of the sensor wire harness connector.
(3) Check for continuity between the sensor return
circuit and the ambient temperature sensor signal
circuit cavities of the black 24-way BCM wire harness
connector. There should be continuity. If OK, go
to Step 4. If not OK, repair the open circuit as
required.
(4) Remove the jumper wire from the ambient temperature
sensor wire harness connector. Check for
continuity between the sensor return circuit cavity of
the black 24-way BCM wire harness connector and a
good ground. There should be no continuity. If OK, go
to Step 5. If not OK, repair the short circuit as
required.
(5) Check for continuity between the ambient temperature
sensor signal circuit cavity of the black
24-way BCM wire harness connector and a good
ground. There should be no continuity. If OK, see the
Trip Computer, Compass, and Thermometer Display
Module diagnosis in this group. If not OK, repair the
short circuit as required.

SERVICE PROCEDURES
COMPASS VARIATION ADJUSTMENT
Variance is the difference between magnetic north
and geographic north. In some geographic locations,
the difference between magnetic and geographic
north is great enough to cause the compass to give
false readings. If this problem occurs, the compass
variance must be set.
To set the compass variance:
(1) Using the Variance Settings map, find your
geographic location and note the zone number (Fig.
1).
(2) Turn the ignition switch to the On position. If
the compass/temperature data is not currently being
displayed, momentarily depress and release the Step
button to step through the display options until you
have reached the compass/temperature display.
(3) Depress both the U.S./Metric, and the Step buttons.
Hold the buttons down until “VAR” appears in
the display. This takes about five seconds.
(4) Release both of the buttons. The current variance
zone number setting will appear in the display.
(5) Press and release the U.S./Metric button to
step through the zone numbers, until the zone number
for your geographic location appears in the display.
(6) Press the Step button to enter this zone number
into the compass unit memory.
(7) Confirm that the correct directions are now
indicated by the compass.


COMPASS CALIBRATION
CAUTION: Do not place any external magnets, such
as magnetic roof mount antennas, in the vicinity of
the compass. Do not use magnetic tools when servicing
the overhead console.
The electronic compass unit features a self-calibrating
design, which simplifies the calibration procedure.
This feature automatically updates the
compass calibration while the vehicle is being driven.
This allows the compass unit to compensate for small
changes in the residual magnetism that the vehicle
may acquire during normal use. Do not attempt to
calibrate the compass near large metal objects such
as other vehicles, large buildings, or bridges.

dnuccio

Overdrive is always engaged unless you press the button. That button is used for when towing or climbing steep hills at speed. With OD off, the trans wont hunt between 3rd and OD the whole time, it will stay in 3rd.
No need to press the button unless doing one of the activities I mentioned.