![background image](http://html1.mh-extra.com/html/carrier/mci-j4500-coach/mci-j4500-coach_operation-and-service-manual_2561383015.webp)
1-7
T-312
1.2.4 Main Control Box
The main control box (See Figure 1-7) includes a main
controller (microprocessor module), expansion output
board, receptacle, quick connectors, connectors and
fuses (F2 and F3). The main controller (microprocessor
module) contains the electronic hardware to measure
inputs and process the outputs to automatically control
the air conditioning and heating system to maintain
temperatures inside the coach. The microprocessor
section has a built in memory facility for checking proper
operation; this includes checks of the program memory,
data memory and analog. It has a self test feature which
is executed when the system is first powered up. The
expansion board drives six discrete outputs in addition
to the standard outputs from the controller.
1. Connector (MA)
2. Connector (MB)
3. (Not Used)
4. Fuse (F2)
5. (Not Used)
6. Fuse (F3)
7. (Not Used)
8. Quick Connector (QC1)
9. Connector (KA)
10. Connector (KB)
11. Connector (MA)
12. Quick Connector (QC2)
13. Connector (MB)
14. Relay
15. Expansion Board
16. Main Controller
17. Packard Connector Pins L thru Y
18. Packard Connector Pins A thru K
19. Coach Interface Connector
20. Model/Serial Number Plate (Box)
21. Model/Serial Number Tag (Controller)
11
10
9
8
7
6
5
4
3
2
1
21
20
18
17
16
15
19
13
12
20
14
Figure 1-7. Main Control Box