Control System Unresponsive; Blank Display; Uim Inoperable - A.O. Smith BTX-100 Service Handbook

ULTRA HIGH EFFICIENCY POWER VENT/POWER DIRECT VENT - SERVICE MANUAL

CONTROL SYSTEM UNRESPONSIVE

DISPLAYED MESSAGE
CONDITION/INDICATES
UIM Display Is Blank
On/Off is turned off
Water heater is not plugged in
Tripped Breaker - Blown Fuses
120 VAC power supply problems
24 VAC power supply problems
Defective transformer
Wiring or plug/socket connection problems
UIM communication cable problems
Important Service Reminder:
When performing any troubleshooting steps outlined
in this service manual always consider the wiring
and connectors between components. Perform a
close visual inspection of all wiring and connectors
to a given component before replacement.
Ensure wires were stripped before being crimped in
a wire connector, ensure wires are crimped tightly in
their connectors, ensure connection pins in sockets
and plugs are not damaged or worn, ensure plugs
and sockets are mating properly and providing good
contact.
Failure to perform this critical step or failing to
perform this step thoroughly often results in
needless down time, unnecessary parts
replacement, and customer dissatisfaction.
UIM does not respond to any user input using the
operational and/or Up and Down buttons.
Water heater may be maintaining water temperature
at the last saved setting or may not be operating at
all.
Technical Literature Department
UIM is Inoperable
Servicing should only be performed by a Qualified Service Agent
• Ensure the on/off switch is on and working -
replace switch if defective.
• Check communication cable connections at
UIM's J2 Socket (page 27) and the CCB's J16
Socket (page 36). Secure power and install a
new comm cable. (standard Cat 5 network
cable).
• Closely inspect communication ports on CCB
and UIM for damage or wear.
• Ensure 120 VAC power is properly connected in
the junction box on the back of the water heater.
• Ensure 120 VAC is supplied to CCB's J3 Socket
pins 1 & 3. Hot wire to pin 1, neutral wire to pin 3
(page 36).
• Check 120 VAC to transformer primary winding
at CCB's J1 socket pins 1 & 3 (page 36) with J1
plug removed, power on.
• Check J1 plug and J1 socket on the CCB for
wear or damage. Ensure plugs and sockets are
mating properly and providing good contact.
• Check for 24 VAC from transformer secondary
winding at CCB's J1 socket pins 4 & 5 with J1
plug inserted, power on. If 24 VAC is not present
AND the two checks above were performed and
the results were successful - replace the trans-
former. Check all wiring for shorts before power-
ing up the new transformer.
• Call the technical support phone number shown
on the water heater labeling for further assis-
tance if the problem has not been corrected
after performing the procedures outlined here.
• Ensure Ribbon Cable from the Button overlay is
inserted correctly in UIM J3 Socket (page 27).
• Call the technical support phone number shown
on the water heater labeling for further assis-
tance if the problem has not been corrected
after performing the procedures outlined here.
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CHECK/REPAIR
Ashland City, TN © 2008