SERVICE PROCEDURE D24-IThermostat CircuitTesting
CAUTION
Be Careful When Making Voltage
Measurements or Jumping Terminals
Not to Damage or Deform Connectors or
Connector Pins.
DANGER
120 volt exposure. To avoid personal injury,
use caution while performing this procedure.
THERMOSTAT CIRCUIT BY-PASS
Turn power “OFF” to water heater and
locate thermostatboard inside control box
of water heater. Disconnect YELL OW wires
from thethermostat board atlocation
“N.O.” & “COM”. Use a jumper to connec t
these two wires together
(see photos 4 &5).
Does pilot and main burner operate?
3
5
With power on to water heater,
Verify Primary and secondary volt age at
the transformer
(see photo 3)
Turn power on to water heater.
Does LED on ignition module illumin ate?
(see photo 6)
This procedure assumes the flue damper is in working order. Be sure damper opens under its ownpower when the
thermostat circuit is by-passed. Damper must be open or removed during this test. Do not force damper open using your
hands or tools.
Y
N
Y
N
Verify transformer voltage
(see photo 3)
See pilot operation testing
(page 8)
Disconnect ORANGE potentiometer (temp
adjustment dial) wires from therm ostat
board (seephoto 7)
DANGER
Do not leave thermostat jumper in
place for normal operation.
Turn power “OFF”.
Removejumper and re-connect wiresto
thermostat board. Wires are iden tified for
proper connection to board.
Check potentiometer for proper res istance values of:
Greatert hen 4800 Ohms with dial at minim um setting.
Less than 50 Ohms with dial at maximum setti ng.
(see photo 8).
Are readings correct?
Replace potentiometer
Check Thermisters
(see page7)
Y
N
7
8
4
Rear terminals
primary
(120 VAC)
Forward terminals
secondary
(24 VAC)
6
LED Location
Page 6
6