American Standard 50A65-475 Manual page 38

Diagnosing the V/S Vent Motor with the V/S Troubleshooter
R
B
Check diagnostic RED LED on the Integrated Furnace
Control (IFC) for a fault before removing the furnace
blower door on downflow models. With no Variable
Speed Vent Motor operation, the IFC diagnostic RED
LED will be flashing three times.
1. Turn power off to furnace.
2. Unplug the Variable Speed Vent Motor harness
plug # E10 from the IFC and plug the harness into
the Variable Speed Troubleshooter.
3. Remove the field wiring from the "R" terminal on
the furnace Low Voltage Terminal Board (LVTB).
Connect a wire from the "R" terminal of the furnace
LVTB to the "R" terminal of the Variable Speed
Troubleshooter. Connect another wire from the
"B" terminal of the furnace LVTB to the "B" termi-
nal of the Variable Speed Troubleshooter.
Caution
Do not reverse these wires; the Variable Speed Motor
may start but will not test out correctly. Repower the
furnace. 24 VAC must be present at the furnace LVTB
terminals "R" and "B" for this test procedure.
4. With the Variable Speed Troubleshooter switch in
the "OFF" position, does the GREEN LED on the
Variable Speed Troubleshooter blink on and off
brightly?
YES: Go to Step #5.
NO: Go to Step #8A.
Variable Speed Draft Inducer Troubleshooter
R1
D1
C1
R2
R3
LO
S1 OFF
HI
36
GREEN LED
D3
RPM/STATUS
12 VDC
D2
Common
R4
Lo Enable
Hi Enable
R5
AMERICAN STANDARD, INC.
PUB NO. 34-3404-01
5. Turn the Variable Speed Troubleshooter switch to
the LOW position. Does the Variable Speed Vent
Motor start?
YES: Go to Step #6.
NO: Go to Step #9.
6. Does the Variable Speed Troubleshooter GREEN
RPM/Status LED come on dimly?
YES: Go to Step #7.
NO: Place a jumper across the low pressure
switch; the troubleshooter GREEN LED
should come on. If the GREEN LED does
not come on, check for 24 VAC to the low
pressure switch, out of the low pressure
switch and on to the Variable Speed Motor
Plug pin #9. If 24 VAC is not present at
the Variable Speed Vent Motor Plug pin
#9, repair as needed. If voltage is present
at pin #9 and the GREEN LED does not
come on, replace the Variable Speed
Vent Motor.
P1
PIN 1