Blower - A.O. Smith BTH 120 Service And Parts Manual

Blower wires (CN 2), igniter wires (CN 5), gas valve pressure switches and flame sense (CN6) plug directly
into blower speed reduction board.
The cables from the blower speed reduction board plug into the control board recepticles CN 2, CN 5, and
CN 6.
• 120 VAC present at CN 2 term 1 to gnd.
• Blower not running
• Tank is calling for heat
STEP 9A. Check for 120 VAC from blower speed reduction board plug (CN 2) term 1 (black wire) to
ground.
IF...
120 VA C is not present
120 VA C is present
STEP 9B.
IF ...
blower runs but does not reduce
speed during igniter warm up or stops
during igniter warm up
blower operates OK
A. O. Smith Water Products Company
Irving, Texas 2000©
TROUBLESHOOTING
STEP 9A - BLOWER SPEED REDUCTION TEST
BTH 250 ONLY
HAS BLOWER SPEED REDUCTION BOARD
THE N
replace the blower s
replace the blower
STEP 9A
STEP 9B - BLOWER TEST
THEN
replace blower spee
go to Step 10.
*
Voltage from blower at low speed
will be approximately 80 VAC.
26
120 Volts on meter
*
STEP 9B
Service Handbook
Training Department