Carrier 58MTB - Manual (Page 15)

15
SERVICE
To initiate the component test sequence, shut OFF the room thermostat or
disconnect the "R" thermostat lead. Briefly short the TEST/TWIN terminal to the
"Com 24V" terminal. Status LED will flash last status code and then turn ON the
inducer motor. The inducer motor will start in HIGH speed and remain on HIGH
speed until the end of the test then shift to LOW speed for 7 to 15 seconds. The hot
surface ignitor, blower motor LO HEAT speed, blower motor HI 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. When the blower is turned OFF the inducer will
be switched to low-speed for 10 seconds.
CONTINUOUS OFF - Check for 115VAC at L1 & L2, & 24VAC at SEC-1 & SEC-2.
CONTINUOUS ON - Control has 24VAC power.
RAPID FLASHING - Line voltage (115VAC) polarity reversed. If twinned,
refer to twinning kit instructions.
LED CODE
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.
STATUS
11 NO PREVIOUS CODE - Stored status codes are erased automatically after 72
hours. On RED LED boards stored status codes can also be erased when
power (115 VAC or 24 VAC) to control is interrupted.
12 BLOWER ON AFTER POWER UP (115 VAC or 24 VAC) -Blower runs for the
selected blower off-delay time, if unit is powered up during a call for heat
(R-W/W1 closed) or (R-W/W1) opens during blower on-delay.
13 LIMIT CIRCUIT LOCKOUT - Lockout occurs if a limit or flame rollout switch is
open longer than 3 minutes. - Control will auto reset after three hours.
- Refer to #33.
14 IGNITION LOCKOUT - Control will auto-reset after three hours. Refer to #34.
21 GAS HEATING LOCKOUT - Control will NOT auto reset.
Check for: - Mis-wired gas valve - Defective control (valve relay)
22 ABNO RMAL 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 HIGH-HEAT PRESSURE SWITCH OR RELAY DID NOT CLOSE OR
REOPENED
Control relay may be defective, refer to status code #32
32 LOW-HEAT PRESSURE SWITCH DID NOT CLOSE OR REOPENED - If
open longer than five minutes, inducer shuts off for 15 minutes before retry. If
opens during blower on-delay period, blower will come on for the selected
blower off-delay. Check for: - Excessive wind - Restricted vent
- Defective inducer motor - Low inlet gas pressure (if LGPS used)
- Defective pressure switch - Low inducer voltage (115 VAC)
- Inadequate combustion air supply - Proper vent sizing
- Disconnected or obstructed pressure tubing
33 LIMIT CIRCUIT FAULT - Indicates a limit or flame rollout, switch is open.
Blower will run for 4 minutes or until open switch remakes whichever is longer.
If open longer than 3 minutes, code changes to lockout #13. If open less than
3 minutes status code #33 continues to flash until blower shuts off. Flame rollout
switch requires manual reset. Check for: - Dirty filter or restricted duct system
- Proper vent sizing - Restricted vent - Loose blower wheel - Excessive wind
- Defective blower motor or capacitor - Defective switch or connections
- Inadequate combustion air supply (Flame Roll-out Switch open).
34 IGNITION PROVING FAILURE - Control will try three more times before lock
out #14 occurs. If flame signal lost during blower on-delay period, blower will
come on for the selected blower off-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)
- Manual valve shut-off - Control ground continuity
- Gas valve defective or gas valve turned off - Low inlet gas pressure
- Inadequate flame carryover or rough ignition - Defective Hot Surface Ignitor
- Flame sensor must not be grounded
- Green/Yellow wire MUST be connected to furnace sheet metal
43 LOW-HEAT PRESSURE SWITCH OPEN WHILE HIGH-HEAT PRESSURE
SWITCH IS CLOSED - Check for: - Disconnected or obstructed pressure tubing
- Mis-wired pressure switches - Low-heat pressure switch stuck open
- Low inlet gas pressure (if LGPS used)
45 CONTROL CIRCUITRY LOCKOUT Auto-reset after one hour lockout due to;
- Gas valve relay stuck open - Flame sense circuit failure
- Software check error
Reset power to clear lockout. Replace control if status code repeats.
If status code recall is needed, briefly remove then reconnect one main limit wire
to display last stored status code. Repeat remove-and-reconnect four more times
for previous four status codes, after which the five codes repeat. Status code 11
will display when less than four previous status codes exist. On RED LED controls
do not remove power or blower door before initiating status code recall.
COMPONENT TEST
327885-101 REV. B
A02258
Fig. 21 -- Service Label
58MTB