Carrier Understanding Furnace Status: Code 24 - Secondary Voltage Fuse is Open

SERVICE

If status code recall is needed, do not remove power or blower door. Briefly remove and then reconnect one main limit wire to display stored status code.

LED CODE STATUS

CONTINUOUS OFF - Check for 115VAC at L1 and L2, and 24VAC at SEC-1 and SEC-2.

CONTINUOUS ON - Control has 24VAC power.

RAPID FLASHING - Line voltage (115VAC) polarity reversed. If twinned, refer to twinning kit instructions.

EACH OF THE FOLLOWING STATUS CODES IS A TWO DIGIT NUMBER WITH THE FIRST DIGIT DETERMINED BY THE NUMBER OF SHORT FLASHES AND THE SECOND DIGIT BY THE NUMBER OF LONG FLASHES.

11NO PREVIOUS CODE - Stored status codes are erased when power

(115VAC or 24VAC) to control is interrupted or 48 hours after each fault is cleared.

12BLOWER ON AFTER POWER UP (115VAC or 24 VAC) - Blower runs for 90 seconds, if unit is powered up during a call for heat (R-W closed).

13LIMIT OR FLAME ROLL-OUT SWITCH LOCKOUT - Control will auto reset after three hours. Reset switch or replace fuse link. Refer to #33.

14IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to #34.

21GAS HEATING LOCKOUT - Control will NOT auto reset.

Check for: - Mis-wired gas valve -Defective control (Valve relay)

22ABNORMAL FLAME-PROVING SIGNAL - Flame is proved while gas valve is de-energized. Inducer will run until fault is cleared.

	Check for:	- Leaky gas valve		- Stuck-open gas valve
23	PRESSURE SWITCH DID NOT OPEN - Check for:
	- Obstructed pressure tubing.		- Pressure switch stuck closed.
24	SECONDARY VOLTAGE FUSE IS OPEN
	Check for:	- Short circuit in secondary voltage (24VAC) wiring.
31	PRESSURE, DRAFT SAFEGUARD, AUX-LIMIT SWITCH (when used*) OR BLOCKED
	VENT SWITCH (when used) DID NOT CLOSE OR REOPENED
	(DOWNFLOW ONLY*) If open longer than five minutes, inducer shuts off for 15
	minutes before retry. Check for:			- Proper vent sizing
	- Low inducer voltage (115VAC)			- Defective inducer motor
	*- Defective Blower motor or capacitor			- Restricted vent
	- Defective pressure switch			- Excessive wind

-Inadequate combustion air supply

-Disconnected or obstructed pressure tubing

If it opens after trial for ignition period, blower will come on for 90 second recycle delay.

33LIMIT OR FLAME ROLL-OUT SWITCH IS OPEN - If open longer than three minutes, code changes to #13. Flame roll-out switch requires manual reset.

Check for: - Defective blower motor or capacitor.

-Dirty filter or restricted duct system.

-Loose blower wheel.

-Defective switch or connections.

-Inadequate combustion air supply (Flame Roll-out Switch or fuse link open).

-Open Flame Roll-out Switch, or fuse link. Manual reset or replace.

34IGNITION PROVING FAILURE - Control will try three more times before lockout #14 occurs. If flame signal lost after trial for ignition period, blower will come on for 90 second recycle delay. Check for:

-Oxide buildup on flame sensor (clean with fine steel wool).

-Proper flame sense microamps (.5 microamps D.C. min., 4.0 - 6.0 nominal).

-Gas valve defective or gas valve turned off.

- Defective Hot Surface Ignitor	- Manual valve shut-off.
- Low inlet gas pressure.	- Control ground continuity

-Green wire MUST be connected to furnace sheet metal.

-Inadequate flame carryover or rough ignition.

-Flame sensor must be ungrounded.

COMPONENT TEST

To initiate the component test sequence, shut OFF the room thermostat or disconnect the "R" thermostat lead. Briefly short the TEST terminal to the "Com 24V" terminal. Status LED will flash code and then turn ON the inducer motor. The inducer motor will run for the entire component test. The hot surface ignitor, blower motor-heat speed, and blower motor-cool speed will be turned ON for 10-15 seconds each. Gas Valve and Humidifier will not be turned on.

9	6	3
8	5	2
7	4	1

LED TEST

HUM Com W Y R G

24V

320615-102 REV. K (LIT)

A99233

Fig. 8ÐService Label

8