Carrier Weathermaster 48P030-100 Controls, Start-Up, Operation, Service, And Troubleshooting page 109

PROBLEM
Low Sensible Capacity in Normal
Cooling Mode
Modulating Valves Not Functioning
Properly
PROBLEM
Burners Will Not Ignite
Inadequate Heating
Poor Flame Characteristics
Burners Will Not Turn Off
PROBLEM
No Heat
Table 87 — Humidi-MiZer Service Analysis (cont)
CAUSE
Valve controlling gas bypass around the
condenser is stuck in an open position or leaking
Valve controlling refrigerant flow to the
condenser is stuck in a position less than 100%
open
General cooling mode problem
Faulty wire connections
EXV board malfunction
Valve is stuck open/closed
Valve is not calibrated properly
Table 88 — Gas Heating Service Analysis
CAUSE
Active alarm.
No power to unit.
No power to IGC (Integrated Gas Control).
Heaters off due to time guard to prevent short
cycling.
Thermostat or occupancy schedule set point
not calling for Cooling.
No gas at main burners.
Water in gas line.
Dirty air filters.
Gas input too low.
Thermostat or occupancy schedule set point
only calling for W1.
Unit undersized for load.
Restricted airflow.
Too much outdoor air.
Limit switch cycles main burners.
Incomplete combustion (lack of combustion
air) results in: Aldehyde odors, CO, sooting
flame, or floating flame.
Unit is in Minimum on-time.
Unit running in Service Test Mode.
Table 89 — Electric Heat Service Analysis
CAUSE
Power failure.
Fuse blown or circuit breaker tripped. Check
CB1, CB2, and CB3.
Thermostat occupancy schedule set point not
calling for Heating.
No 24 vac at primary contactor.
No power (high voltage) to L2 of primary 
contactor.
Bad electrical elements.
See "Modulating Valves Not Functioning Properly."
See "Modulating Valves Not Functioning Properly."
See Table 86.
Check that the valve wiring is properly connected from the valve, entering the
control box and at the EXV board.
Check alarm history for A169 (Expansion Valve Control Board Comm Failure).
Use Service Test to manually manipulate the valve position and confirm supply air
temperature changes during operation.
Run valve calibration through Service Test.
Check valve motor for open or short circuited windings. Shut down power to the
unit and connect ohmmeter probes across the black and white terminals.
Resistance should measure 75 Ohms ±10%. Next, connect ohmmeter probes
across the red and green terminals. Resistance should measure 75 Ohms ±10%.
The meter should not show an "open" or a "short" when a winding leg is measured.
If either occurs, replace the valve.
Run valve calibration through Service Test.
Check active alarms using ComfortLink scrolling
marquee.
Check power supply, fuses, wiring, and circuit breakers.
Check fuses and plugs.
Check using ComfortLink scrolling marquee.
Check using ComfortLink scrolling marquee.
Check gas line for air and purge as necessary. After purging gas line of air, allow
gas to dissipate for at least 5 minutes before attempting to re-light unit.
Drain water and install drip.
Replace air filters.
Check gas pressure at manifold. Refer to gas system adjustment in this manual.
Allow time for W2 to energize.
Decrease load or increase of size of unit.
Remove restriction.
Check economizer position and configuration. Adjust minimum position using
ComfortLink scrolling marquee.
Check rotation of blower, thermostat heat anticipator settings, and temperature
rise of unit. Adjust as needed.
Check all screws around flue outlets and burner compartment. Tighten as necessary.
Cracked heat exchanger, replace.
Unit is over-fired, reduce input. Adjust gas line or manifold pressure.
Check vent for restriction. Clean as necessary.
Check orifice to burner alignment.
Check using ComfortLink scrolling marquee.
Check using ComfortLink scrolling marquee.
Call power company.
Replace fuse or reset circuit breaker.
Check using ComfortLink scrolling marquee.
Check transformer and circuit breaker.
Check safety switches "one-shot" backup and auto limit.
Power off unit and remove high voltage wires. Check resistance of heater,
replace if open.
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REMEDY
REMEDY
REMEDY