Carrier 58MCA Instruction Manual download pdf (Page 15)

11 NO PREVIOUS FAULT - Faults

are erased after 48 hrs or

whenever power (115v or 24v) is

interrupted. Run system through

a heating or cooling cycle to 

check system.

12 BLOWER ON AFTER POWER

UP (115V OR 24V) - Normal 

operation. Blower will run for 90

sec when furnace power is

interrupted during a call for heat,

R-W closed.

13 LIMIT OR FLAME ROLLOUT

SWITCH LOCKOUT -

Limit switch was open longer

than 3 minutes. Auto-reset will

occur after 3 hrs. Flame rollout

switch requires manual reset.

See No. 33

14 IGNITION LOCKOUT - System

failed to ignite gas and prove

flame in 4 attempts. Control will

auto-reset in 3 hrs.

See No. 34

21 GAS HEATING LOCKOUT - 

Turn off power and wait 5

minutes to retry.

Check for:

Unplug ignitor harness from control

center and inititate another 

component test sequence. Check

for 115v between pins 1 and 2 on

the control center. Was 115v present

for the 17-sec period?

Replace control center.

Check for continuity in the harness

and ignitor. Replace defective

component.

Reconnect the R thermostat lead

and set thermostat to call for heat.

Connect voltmeter across gas valve

connections. Does gas valve

receive 24v?

Check connections. If OK, replace

control center.

Does gas valve open and allow gas

to flow?

Check that all gas valves are turned

on. Replace valve.

Do main burners ignite?

Do main burners stay on?

Allow blower to come on and repeat

test to check for intermittent

operation.

Repeat call for heat and check flame

sensor current during trial for ignition

period. Is the DC microamps

below 0.5?

Check connections and retry. If 

current is near typical value and

control will not stay on, replace

control center.

Clean flame sensor with fine

sandpaper and recheck current. 

Current is nominally 4.0 to 6.0 microamps.

Is current near typical value?

Replace electrode.

Will main burner ignite and stay on?

Replace control center.

Fixed.

• Stuck closed gas valve relay

on control.

• Miswire or short to gas valve

wire.

22 ABNORMAL FLAME PROVING

SIGNAL - Flame was sensed

while gas valve was

de-energized. Inducer will run

until fault is cleared.

Check for:

• Stuck open gas valve solenoid

or leak.

• Defective control center.

23 PRESSURE SWITCH WILL

NOT OPEN - Check for:

• Disconnected or obstructed

pressure tubing.

• Defective pressure switch.

24 LOW-VOLTAGE FUSE IS

OPEN - Check for:

• Short in low-voltage wiring

including thermostat leads

shorting to ductwork or

furnace cabinet. Disconnect

thermostat leads to isolate

short circuit.

31 PRESSURE SWITCH WILL

NOT CLOSE OR REOPEN - If

open longer than 5 minutes,

inducer shuts off for 15 minutes

before retry. 

Check for:

• Proper vent sizing or pitch or

sag.

• Vent restrictions or high winds.

• Defective inducer motor.

• Low line voltage (115v).

• Motor start capacitor.

• Low inlet gas pressure.

• Defective pressure switch or

connections. If it opens after

trial for ignition period, blower

will come on for 90 sec

recycle delay.



• Inadequate combustion air.

33 LIMIT OR FLAME ROLLOUT 

SWITCH IS OPEN - If 

limit switch is open longer than 3

minutes, code changes to No. 13.

Check for:

• Blower motor failure.

• Motor start capacitor.

• Open flame rollout switch, 

manual reset.

• Dirty filter.

• Defective limit switch or 

connections.

• Loose blower wheel.

34 IGNITION PROVING FAILURE -

If flame is not sensed during the

trial for ignition period, the control

will repeat the ignition sequence

3 more times before going into

lockout, No. 14.

If flame signal is lost after trial for

ignition period, blower will come

on for 90-sec recycle delay.

Check for the following items first

before proceding to the next step.

• Gas valve turned off.

• Manual shut-off valve.

• Green wire must be connected

to furnace sheet metal.

To determine whether the

problem is in the gas valve,

ignitor, or flame sensor, the

system can be operated in the

component test mode to check

the ignitor. First, remove the

R thermostat connection from the

control center and initiate the

component test sequence. Does

the ignitor glow orange/white hot

by the end of the 17-sec warm-up

period?

Check for:

• Inadequate flame carryover on

rough ignition.

• Low inlet gas pressure.

YES

•

Inadequate combustion air 

supply (flame rollout switch

only).

A96219

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