R - B 11
Solving Err 91 Comm Errors
Note: If there is no 24 volts AC power at some of the
communicating components, the BM LED may be
very dim or out, or may be flashing very fast. An
error code or ERR 89 may have been seen at the
comfort sensor.
Yes: Remove all wires from D terminal at the furnace
IFC or air handler terminal board. Does the BM LED
now come on? If the BM LED does not come on,
replace the furnace IFC or the air handler control
board. If the BM LED comes on, go to Step 11.
No: Restore 24 volts AC power and then test control
system for proper operation.
Step 3
The amber COM LED will normally flash rapidly for
a few seconds when the system is powered up and
then go to a slow flash rate of 1, 2, or 3 or more
flashes.
What is the amber COM LED doing?
Slowly flashing one flash and after three minutes
it then goes to a fast flash. This means the furnace
IFC or the air handler control board is not
communicating with anything. Go to Step 7.
Flashing in groups of 2, 3 or more flashes. This
means the furnace IFC or the air handler control board
is communicating with the Comfort Sensor and some
of the other components in the system. The number
of flashes in the group is the number of things that
are communicating with each other. Go to Step 4.
Flashing in groups of 2, 3 or more flashes for
three minutes and then goes to a fast flash rate.
This means that the Comfort Sensor and the furnace
IFC or air handler control board are not
communicating. Go to Step 6.
Step 4
How many communicating components are
connected in this system?
The furnace IFC or air handler count as one, the
thermostat counts as two, the outdoor unit counts as
three (if the outdoor unit is the communicating type)
and a telephone access module would count as four.
Does the number of communicating components
agree with the flash code count of the furnace
IFC or air handler COM LED?
Yes: Go to Step 5.
No: Go to Step 8.
Step 5
At the User Interface scroll to the INDOOR ALERT
screen. Press the ENTER button to see the alert
message (See Figure 20.)
What is now displayed?
Figure 20
? ? ?
If IND COMM ERR is displayed (Figure 21), go to the
Troubleshooting Chart IND COMM ERR secton (Page
4).
Figure 21
IND COMM ERR
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