A.O. Smith BTH 120 Service Handbook - Troubleshooting
A. O. Smith Water Products Company
Service Handbook
Irving, Texas 2000
©
Training Department
27
STEP 10. CONTINUITY CHECK OF EACH PRESSURE SWITCH - TERMINAL TO TERMINAL.
(Meter buzz indicates continuity)
IF…
THEN
Block inlet switch does not show continuity
replace
Block inlet switch does show continuity
continue
Blower proving switch does not show continuity
continue
Blower proving switch does show continuity
replace
Low gas pressure switch does show continuity
continue
Blocked outlet pressure switch does not show continuity replace
Blocked outlet pressure switch does show continuity
continue
Low gas pressure switch (BTH 120 and 250 only) does
not show continuity
check
replac
24 VAC check through pressure switches – blower off.
• Power on
• Tank not calling for heat
• Multimeter set to check for 24 VAC
Note: Power flows from bottom terminal to top terminal of each switch – check wiring
STEP 10 - CONTINUITY PRESSURE SWITCH TEST - ALL MODELS
TROUBLESHOOTING
Power Off