R - B 8
Solving Err 91 Comm Errors
Figure 14
This DC voltage should be going up and down
between 0.50 volts DC and 1.07 volts DC. The
voltmeter will stop reading at times and then start
reading again.
Yes: Go to Step 5.
No: Go to Step 4.
Step 4
Set the Comfort Control thermostat to call for blower
operation.
Is there DC voltage between the gas furnace IFC
plug E8 terminal TX and GND? (See Figures 15a
& 15b.) This DC voltage should be going up and
down between 0.5 volts DC and 1.07 volts DC. This
voltage reading will stop reading at times and start
again.
Figure 15a
Figure 15b
Yes: Repair or replace the low voltage harness going
from the gas furnace IFC plug E8 or the air handler
plug to VS COMM going to the indoor blower low
voltage plug.
No: Replace the gas furnace IFC or the air handler
control board.
Step 5
De-power the gas furnace or the air handler. At the
gas furnace IFC or the air handler control board,
remove the wire from the terminal RX in the low
voltage plug going to the indoor blower low voltage
plug. When the RX wire is removed from the low
voltage plug, put the low voltage plug back into the
gas furnace IFC or the air handler control board.
Detail 1: Push down on the wire connector latch clip
on the side of the plug and pull the RX wire from the
low voltage plug. Plug the low voltage plug back
into the IFC (See Figure 16.)
To Next Page
Loading...
