Carrier PC 111 Air Conditioner User Manual


 
51
RELAY BOARD TROUBLESHOOTING — The relay board
contains 13 electromechanical relays. The small relays are
24 vac, and the large relays are 115 vac. These relays are con-
trolled by the processor through the ribbon cable attached to
the relay board.
The following procedure can be used to check out the oper-
ation of the relays. To do this, turn the control ON/OFF switch
to the OFF position, and remove the wiring connectors con-
nected to pin terminal connectors J5 and J6. Set the meter for
resistance. If the contacts do not close at the required quick test
step, check the relay outputs from the processor board.
Relay Board Checkout (Fig. 5)
Step 1 — Low-voltage relay resistance check.
1. Turn switch to OFF position.
2. Remove plug connection from terminal strip J6.
3. Set meter to measure resistance. Connect negative test
lead to both terminals 11 and 12 of J6.
4. Turn switch to ON position and go into Quick Test mode.
5. Place other meter lead on terminals shown in Table 27
and check resistances at each quick test step.
6. If these resistances are not correct and relay board outputs
from processor board have been checked out, replace re-
lay board.
Step 2 — High-voltage relay resistance check.
1. Turn switch to OFF position.
2. Remove plug connection from terminal connector J5.
3. Connect negative test lead to terminal 8.
4. Check the resistance between terminals 8 and 5 before
entering Quick Test mode. The resistance should be
infinity.
5. Turn switch to ON position and go into Quick Test mode.
6. Place other meter lead on terminals shown in Table 28
and check resistance at each quick test step.
7. If these resistances are not correct and relay board outputs
from processor board have been checked per Processor
Board Checkout section on page 48, replace relay board.
DISPLAY BOARD CHECKOUT
Step 1 — Check the Output Voltage from Processor Board
to the Relay Board — Refer to Step 6 — Display Board Con-
nection Checkout section on page 49.
Table 27 Terminal Strip J6 Connection
Resistance Reading
LEGEND
NOTE: Pins shown in
boldface
type will be energized for only
10 seconds. All other pins will be energized continuously while at the
proper quick test step. The control will remain in the Quick Test
mode for only 10 minutes unless the display button is pressed.
Table 28 Terminal Strip J5 Connector
Resistance Reading
LEGEND
Step 2 — Check the Display LEDs
1. Enter Quick Test mode.
2. If 88 is not displayed, replace display board.
Step 3 — Check Set Point Potentiometer
— Advance the
display to quick test step 1.9. to determine if this potentiometer
is set and connected properly.
Step 4 — Check Display Switch
— Press switch. If switch
does not click, it is faulty and the display will be energized con-
tinuously. The switch is an integral part of display board and
cannot be replaced separately.
ACCESSORY BOARD CHECKOUT — The accessory board
can be completely checked using quick test steps 2.0., 2.2., and
2.3. It can also be checked out as follows:
1. Remove the accessory board connector from the proces-
sor board and connect an ohmmeter to terminals 3 and 4
on the connector. Numbers are marked on the connector.
See Fig. 15.
2. Set the meter to 10,000 ohms. The resistance value ob-
tained should be 3,333 ohms. Adjust the potentiometers
and the resistance value should not change.
3. Connect the ohmmeter to terminals 3 and 6. As the reset
limit potentiometer is turned clockwise, resistance should
increase from 0 to approximately 3,400 ohms.
4. Connect the ohmmeter to terminals 3 and 5. As the econ-
omizer minimum position potentiometer is turned clock-
wise, resistance should increase from 0 to approximately
3,400 ohms.
5. Connect the ohmmeter to terminals 3 and 2. As the
warm-up set point potentiometer is turned clockwise,
resistance should increase from 0 to approximately
3,400 ohms.
If any of the Steps 1 through 5 result in any other ohm read-
ing, replace the board; it cannot be serviced.
TWO-STEP DEMAND LIMIT CONTROL MODULE
(DLCM) TROUBLESHOOTING — If a problem is suspected
in the DLCM board, use the following test procedure:
The board can only be checked when it is connected to the
processor and the processor is energized so that the DLCM is
supplied with 5 vdc power. The terminals referenced are shown
in Fig. 16. Potentiometers P1 and P2 refer to the DLCM poten-
tiometers.
QUICK TEST
STEP NO.
J6 PIN NUMBERS
12345678
1. to 2.3.
∞∞∞∞∞∞∞∞
2.4.
∞∞∞∞∞∞
0
2.5.
∞∞∞∞∞∞
0
2.6.
∞∞∞∞∞∞∞∞
2.7.
∞∞∞∞∞∞∞∞
2.8.
∞∞∞∞∞∞∞∞
2.9.
0
∞∞∞∞∞∞∞
3.0.
0
∞∞∞∞∞∞
3.1.
∞∞
0
∞∞∞∞∞
3.2.
∞∞∞∞
0
∞∞∞
3.3.
∞∞∞∞∞
0
∞∞
Infinity
QUICK TEST
STEP NO.
J5 PIN NUMBERS
12345
1. to 2.5.
∞∞∞∞
0
2.6
00
∞∞
0
2.7.
0
0
0
2.8.
0
∞∞
00
2.9. to 3.3.
0
∞∞
0
Infinity
IMPORTANT: Be careful to avoid damaging the con-
nector or the processor board when taking the voltage
readings.