Carrier 50LJ User Manual download pdf (Page 32)

Symptom: Evaporator Fan Will Not Operate.

1. Turn unit power off and disconnect plug PI from the

control board.

2. Install a jumper across Pin R and Pin G at plug PI on

the control board.

3. Turn unit power on and check if the evaporator-fan con

tactor (IFC) coil has been pulled in. If the contactor has

not been pulled in, check the voltage across the IFC coil.

If there is voltage at this point, the IFC contactor is de

fective. If there is no voltage, proceed to Step 4.

4. Turn unit power off and disconnect plug P4 from the

control board.

5. Turn unit power on and check for continuity across Pin

6 and Pin 3 at plug P4 on the control board. If there is

no continuity, the board is defective. Replace control

board. If there is continuity, then there is a bad con

nection between the board and plug P4. Correct the

connection.

6. Turn unit power off. Reconnect plug PI (if troubleshoot

ing is complete) and plug P4.

Symptom: Condenser Fan No. 1 Will Not Operate.

1. Turn unit power off. Disconnect plugs PI and P3 from

the control board.

2. Check for continuity between Pin 8 at plug P3 on the

control board and Pin Y1 on the control board. If there

is no continuity, the board is defective. If there is con

tinuity, either the connection is bad between plug P3

and the control board or the problem is external to the

board. Reconnect plug PI (if troubleshooting is com

plete) and plug P3 to the board.

Symptom: Condenser Fan No. 2 Will Not Operate.

Check operation of condenser fan no. 1. If fan no. 1 op

erates properly, the problem is external to the board.

Symptom: Compressor No. 1 Will Not Operate.

1. Turn unit power off. Disconnect the 2 wires attached to

the terminals marked SCI.

2. Check continuity between the 2 wires. If there is no con

tinuity, the problem is external to the control board

(possibly the pressure switches). If there is continuity,

proceed to Step 3.

3. Reconnect the wires removed in Step 1 above.

4. With the unit power still off, disconnect plug PI from

control board. Install a jumper wire across Pin R and

Pin Y1 at plug PI on the control board.

5. Connect a voltmeter across the coil for Compressor no.

1 contactor.

6. Energize unit and monitor the voltage for a few

seconds.

IMPORTANT: Do not run compressor too long.

7. a.

If proper voltage is indicated at the contactor, but

contactor fails to close, replace contactor.

If voltage is indicated for a few seconds (i.e., the

contactor momentarily pulls in and is then de

energized), the Compressor Lockout (CLO) logic has

shut down the unit. This is an indication that the board

is not sensing proper compressor current, or that one

of the safeties has tripped. Proceed to Step 8 to ver

ify compressor lockout logic operation.

If proper voltage is indicated at the contactor and con

tactor closes, the board is operating properly.

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Carrier 50LJ User Manual Page 32

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