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Mascot ST Tankless Water Heater
Section 7 – Troubleshooting
Diagnostics and suggested corrective actions
This controller is able to record information about the water heater's condition for the ten previous faults or errors. Refer to the 'Error
Code' section of this Manual, (Section 6).
Display
Nothing shown on
display control panel
and blower running at
full speed.
Nothing
is shown in display
control panel and no
other Water Heater
components are
operating.
Nothing is
shown on
control panel,
but water heater is oper-
ating.
TEMPERATURE
RISE TOO
QUICKLY
TEMPERATURE
SENSOR
Condition
Check wiring for short
Panel is not
circuit or incorrect wiring.
receiving power.
Check for 14V output of
panel wire.
Is there 120 Volts at the
Control is not
receiving 120V
manual switch?
power.
Check the water heater
inside power manual switch.
Check for 120 volts at the
line voltage terminal inside
the water heater case.
Check for loose connec-
Occurs when the
tions and proper pin
communication is
alignment/ engagement on
lost from the control
the Control's plug.
to the display.
Cycle power off and on
using water heater power
switch and check for
operation.
Occurs when supply
water temperature
in heat exchanger
Automatically resets after a
rises faster than 2°F
few minutes delay or use
per second during
manual reset.
the
first two minutes the
burner is on.
Occurs when a
Reset using manual.
temperature sensor
Reset screen on control
has electrically
panel. (Power button)
shorted(SHORT) or
has become
disconnected
(OPEN).
Diagnostic
Correct wiring per wiring diagram including con-
nection of transformer to the control.
Push the 'A' button of control panel.
Correct the power supply from the manual
switch.
Turn on the manual power switch inside the
water heater case.
Correct wiring inside the water heater case
using the wiring diagram in this manual.
Check for continuity on the wire harness from
the display to the control panel. See repair parts
section for proper replacement part.
Replace with new display module. See repair
parts section for proper replacement part.
See the message displayed TEMPERATURE
SENSOR and follow procedures for loose
connections.
Check all the temperature readings of the water
heater on the DIAGNOSTICS - TEMPERA-
TURES menu to determine if any sensors are
currently displayed as SHORT or OPEN.
Check wire harness for loose connections and
pin engagement at sensor Connection and
Control module.
If problem persists after checking items above,
replace Control. Refer to the installation manual
32~36page.
7.1 Diagnostics
Corrective Action(s)
Page 53
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