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58SU0A (Series 2 & 3): Troubleshooting Guide
Status Code 13 - Limit Circuit Lockout
Lockout occurs if a limit, draft safeguard, burner thermal switch or blocked vent switch (if used) or blower auxiliary limit switch is open.
Control will auto-reset after three hours. Blower will run for 4 minutes or until limit switch closes, whichever is longer.
STEP
Turn power off, remove the blower access panel, and disconnect the R thermostat lead from the
1.
furnace control board.
2.
Depress the blower door switch. Use a piece of tape to hold it closed. Turn power on
3.
Does status code 13 flash?
4.
Does a different status code flash?
5.
Go to page number indicated in the Index for the section covering the status code.
6.
Jumper R and W thermostat terminals.
7.
Observe the furnace operation for at least 20 minutes or until status code starts flashing.
8.
Does status code 13 flash?
9.
Does a different status code flash?
10.
Fix Problem
11.
Go to page number indicated in Index for CLEANUP AND START- UP INSTRUCTIONS.
12.
Did blower motor start?
Hook an AC voltmeter across PL15 L1 Black (+) and PL15 L2 White (-). Is 115-VAC across PL15 L1
13.
Black (+) and PL15 L2 White (-)?
14.
Is the Black L1 blower lead connected to the BL motor output on the furnace control?
15.
Is the White L2 blower lead connected to one of the Neutral-L2 output taps on the furnace control?
You have an open wire or bad terminal on either the BLACK L1 or WHITE L2 wire between the furnace
16.
control and the blower motor. Repair or replace blower motor harness.
Hook an AC voltmeter across the Blower Heat speed output tap (+) and the blower COM connection (-)
17.
at the 24V MTR tap connections on the furnace control. Is 24-VAC across Blower Heat speed output tap
(+) and the blower COM connection (-)?
Hook an AC voltmeter across the PL16 blower lead attached to heat speed (+) and PL15 Com GREEN
18.
(-) at blower motor. Is 24-VAC across the PL16 blower lead attached to heat speed (+) and PL15 Com
GREEN (-)?
19.
Replace blower motor
You have an open wire on either the heat speed tap or the blower speed COM of the 24V signal wires to
20.
the blower motor.
Remove jumper from the R and W terminals and allow blower motor to run for 10 minutes or until blower
21.
shuts off
22.
Did blower shut off before 10 minutes?
23.
Turn power OFF
24.
Is 24vac across connector terminal PL1-6 and COM-24V on the furnace control?
25.
Turn power off
26.
Disconnect PL1 from furnace control.
Turn power off at main disconnect, remove tape from door switch, and remove jumper across
27.
R and W/W1.
28.
Is blower wheel firmly mounted on motor shaft?
Does the model plug PL4 match the part number specified on the Model Plug Chart in upper left-hand
29.
corner of wiring schematic?
30.
Replace model plug.
Does furnace have the proper limit switch, limit shield, blower baffle (if used), and rear air baffle (if
31.
used)? If so, are the limit switch, limit shield, and heat exchangers properly aligned?
32.
Is blower wheel firmly mounted on the blower shaft?
33.
Do you have continuity across limit switch (LS)?
34.
Allow limit switch (LS) to cool for 10 minutes. Do you have continuity across the limit switch (LS)?
35.
Replace limit switch (LS).
Turn power on and jumper the R and W thermostat terminals. Allow furnace to operate for 20 minutes or
36.
until status code starts flashing
37.
Does status code 13 flash?
38.
Does a different status code flash?
Is the furnace considerably over-fired? (10% or more?) Clock input rate. Do not use manifold pressure
39.
method.
Ensure that gas inlet pressure and orifice is correct. Adjust gas valve pressure to achieve proper input
40.
rate per the Installation, Start Up, and Operating Instructions.
41.
Is temperature rise within range?
42.
Turn power off and install a temperature probe in front of limit switch button.
Turn power on and cycle unit. Does the limit switch open at a temperature at least 15 deg. F. below the
43.
temperature setpoint of the switch? (Example - setpoint of switch is 175 deg. F. but switch opens at a
temperature below 160 deg. F.)
Problem may be related to poor air distribution or excessive pressure drop across the filter. Check filter
44.
and return air grills for blockage. Add turning vanes, more supply openings, or more return air openings.
45.
Does the installation have a bypass humidifier or zoning system bypass?
46.
Is temperature rise of return air from bypass greater than 15 deg. F?
47.
Bypass is oversized. Adjust damper or replace with properly sized bypass.
48.
Can blower speed be adjusted to raise airflow delivered?
Manufacturer reserves the right to change, at any time, specifications and designs without notice and without obligations.
ACTION
11
YES
NO
GO TO
2
3
24
4
5
6
INDEX
7
8
12
9
5
11
11
INDEX
21
13
17
14
15
10
16
10
10
18
29
19
20
10
10
22
24
23
71
30
25
26
27
28
29
24
31
30
10
27
24
33
10
50
34
36
35
37
39
38
5
11
40
41
10
42
45
43
35
44
10
46
48
47
48
10
49
44
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