Microprocessor Replacement And Configuration Service Guidelines; Controller Sensor Checkout - Carrier Supra 950MT Operation & Service Manual

5.18.1

Microprocessor Replacement and Configuration Service Guidelines

a Removing and Replacing the Microprocessor Logic Board:
1. Before removing the microprocessor, disconnect the negative battery cable and attach a grounded wrist
strap (07-00304-00) to your wrist and ground it to a good unit frame ground.
2. Open the roadside side door of the unit and loosen the four bolts holding the cover/microprocessor onto the
front of the control box.
3. Unplug the ribbon cable from the logic board, but leave it connected to the cab command cable. For 950MT
units, unplug the power cable (it does not have a ribbon type cable).
4. Take the new microprocessor from the anti-static bag and install in the control box, following steps 2 through
4 in reverse order.
5. Place the removed microprocessor back into the anti-static bag and part box for return.
BEFORE STARTING THE UNIT: When replacing a microprocessor it is important to check that the
configurations are compatible with the unit into which the microprocessor will be installed.
b To Reach Configuration Fields from Keypad:
1. Place the unit RUN/STOP switch in the STOP position and the I/O switch in the OFF (O) position.
2. With the unit off, locate the serial port plug behind the control panel. Remove the protective cap to gain access
to the wire terminals. Place an insulated jumper wire between wires SPA and SPB at the serial port plug.
3. Place the unit RUN/STOP switch in the RUN position and the I/O switch in the RUN (I) position. The FAULT
light will come on, and the micro display will read CNF1 TV. Remove the jumper wire from the serial port and
reinstall the protective cap. The configuration screen will now remain available for five minutes. Scroll
through the configuration list using the Function key and compare the settings with those shown in the table
on the following page. If any of the configurations need to be changed, continue with step 4 below.
4. To change the configuration selection: (Refer to
a. Bring the configuration to be changed onto the display. Press the Enter key to allow change access to the
displayed configuration.
b. Press either the UP or DOWN keys to display available selections for that configuration. Leave the cor-
rect selection on the screen. The selection display will flash, warning the operator that the displayed
value has not been entered. Press the ENTER key to enter the new selection into memory. The display
will revert to the original selection if no further action is taken for the next five seconds.
c. Continue to scroll through the configuration list by pressing the FUNCTION key. Change any other con-
figurations as required.
5. When finished, turn the RUN/STOP switch to the STOP position, then back to the RUN position to start the unit.
5.18.2

Controller Sensor Checkout

An accurate ohmmeter must be used to check resistance values shown in
Due to variations and inaccuracies in ohmmeters, thermometers or other test equipment, a reading within 2% of
the chart value would indicate a good sensor. If a sensor is bad, the resistance reading will usually be much higher
or lower than the resistance values given in
At least one lead from the sensor (RAS, terminals D1 and E1 or SAS, terminals D2 and E2) must be disconnected
from the unit electrical system before any reading is taken. Not doing so will result in a false reading. Two preferred
methods of determining the actual test temperature at the sensor, is an ice bath at 32°F (0°C) or a calibrated tem-
perature tester.
62-11863
CAUTION
!
Do not allow insulated jumper wire to touch any ground.
Table 5–4.
NOTE
Table 5–7):
Table
5-24
5–4.