49
Control Module Communication
RED LED
Proper operation of the MBB and ECB control boards can be
visually checked by looking at the red status LEDs. When op-
erating correctly, the red status LEDs should blink in unison at
a rate of once every 2 seconds. If the red LED on the ECB is
not blinking, check the DIP switch positions on the board. If
the red LEDs are not blinking in unison, verify that correct
power is being supplied to all modules. A blinking red LED at
the rate of once per second means that software is not loaded
on the board. Also, be sure that the board is supplied with the
current software. If necessary, reload current software. A board
LED that is lit continuously should be replaced.
GREEN LED
The MBB and ECB each have one green LED. The Local
Equipment Network (LEN) LED should always be blinking
whenever power is on. If LEN LED is not blinking, check LEN
connections for potential communication errors (MBB J3, J4,
and J5). Communication between modules is accomplished by
a 3-wire sensor bus. These 3 wires run in parallel from module
to module. The J4 connector on the MBB also provides both
power and communication directly to the scrolling marquee
display. The J5 connector on the MBB provides a LEN inter-
face at the field connection terminal (TB).
YELLOW LED
The MBB has one yellow LED which is used to indicate CCN
communication activity. The Carrier Comfort Network
®
(CCN)
LED will blink during times of network communication.
Communication Failures
If the scrolling marquee or Navigator display Communication
Failure or the green or yellow LEDs do not flash on the boards
then the problem could be the communication chip on one of
the control boards (MBB or ECB). Disconnect all the LEN and
CCN plugs from the board and use an ohm meter to measure
the resistance on the communication pins of the boards to de-
termine if the board is bad. If the reading is less than half the
value indicated in Table 15, then the board needs to be re-
placed.
NOTE: The resistive values should be read when the board is
powered off and the unit is locked out.
Table 15 — LEN and CCN Communication Resistances
Device
Board Serial
Number
(LEN) Resistance between Pins/Connector (CCN) Resistance between Pins/Connector
Pins 1 to 3 Pins 1 to 2 Pins 2 to 3 Pins 5 to 7 Pins 5 to 6 Pins 6 to 7
MBB
Prior to 4702N
15K
J3, J4, & J5
7.5K
J3, J4, & J5
7.5K
J3, J4, & J5
15K
J5
7.5K
J5
7.5K
J5
Starting 4702N
18.9K
J3, J4, & J5
9.9K
J3, J4, & J5
9.9K
J3, J4, & J5
18.9K
J5
9.9K
J5
9.9K
J5
ECB
Prior to 0803N
5.9K
J2
5.2K
J2
5K
J2
———
Starting 0803N
18.9K
J2
9.9K
J2
9.9K
J2
———
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