- 9 -
START HERE - If a problem exists, the service technician should always begin
troubleshooting here.
Special Note
: All voltmeters are not the same - your voltage readings will vary. This applies to the entire content of this troubleshooting manual.
They are not absolute values. Correct 115-VAC VOLTAGE, CURRENT, and power MEASUREMENTS CANNOT BE TAKEN ON
MODULATING FURNACES UNLESS USING A TRUE rms METER.
STEP
ACTION
YES
NO
GO TO
1.
DO NOT REMOVE THE BLOWER DOOR! Record status of AMBER LED. See
Service/Status Code Instructions.
Is AMBER LED status light ON SOLID, alternately flashing bright-dim-bright-dim like a
heartbeat, or flashing ON and OFF?
2
19
2.
Is AMBER LED status light ON SOLID?
3
4
3.
Go to page number indicated in the Index for the section covering AMBER LED ON SOLID.
INDEX
4.
Is the AMBER LED status light alternately flashing bright-dim-bright-dim like a heartbeat?
7
5
5.
Determine status code. The status code is a single or two digit number with the first number
determined by the number of short flashes and the second number after the (+) sign is the
number of long flashes.
6
6.
Go to page number indicated in the Index for the section covering the status code.
INDEX
7.
Remove blower door and depress door switch. Use a piece of tape to hold it closed. To
retrieve previous codes, disconnect the communication connector PL7 (if used) or the R
thermostat lead (if used) from the furnace control board and wait for the blower to turn off if
it is running. Put setup switch SW1-1 in the ON position and record the status codes listed in
the status code history. The status codes will flash in the order of occurrence. Read status
codes until the heartbeat flashes. After the heartbeat flashes several times the status codes
will repeat.
8
8.
Was there a previous status code other than the heartbeat?
Note:
Status codes are erased after 72 hours or can be manually erased by putting setup
switch SW1-1 in the ON position and jumpering R, W/W1, and Y/Y2 simultaneously until
the heartbeat flashes.
9
10
9.
Go to page number indicated in the Index for the section covering the first previous status
code.
INDEX
10.
Does the problem appear to be low cooling airflow?
11
12
11.
Go to page number indicated in Index for the section covering IMPROPER COOLING
AIRFLOW.
INDEX
12.
Set thermostat to call for heat and set the thermostat fan control to AUTO position if
equipped.
13
13.
Does the furnace respond to the call for heat?
14
28
14.
Observe operation of furnace for 20 minutes or until AMBER LED status light starts
blinking.
15
15.
Does the AMBER LED status light blink ON/OFF slowly with short flashes or a combination
of short and long flashes?
5
16
16.
Is the temperature rise below the range specified on the rating plate when the unit is operating
in minimum, and/or maximum heat?
Note:
If the temperature rise is above the range specified on the rating plate refer to the Start-
Up and Adjustment section in the Installation, Start-Up, and Operating Instructions.
17
18
17.
Go to page number indicated in Index for the section covering MINIMUM AND/OR
MAXIMUM HEAT TEMPERATURE RISE TOO LOW (COLD BLOW).
INDEX
18.
Go to page number indicated in Index for CLEANUP AND START-UP INSTRUCTIONS.
INDEX
19.
Make sure power is being supplied to the furnace.
20
20.
Check fuses, breakers, or manual disconnects to be sure they are correctly set. If not, reset
them and go back to step 1.
21
21.
Remove blower door and depress door switch. Use a piece of tape to hold switch closed.
22
22.
Is 115-vac across L1 and L2?
24
23
23.
Turn power off. Check continuity of power leads and door switch. If necessary repair power
leads and/or replace door switch.
18
24.
Is 24-vac across SEC-1 and SEC-2?
32
26
25.
Replace the modulating furnace control.
18
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