PDX SERVICE PROCEDURE VI
Gas Control/Thermal Well Testing and
Replacement
PDX Series
Thermal Well Testing
Thermal welltesting
Position gas cont rol power switch to
the “OFF” position a nd disconnect
thermal well harne ss from gas
control.
N
Y
Using a multi-meter set to the ohms setting, insert one meter probe (see caution)
into center wire position of thermal well connector, insert the second probe (see
caution) into either of the outside wire positions (s ee photo 23).
Alternate the prob e on the outside positio n to the opposite outside wire position
(see photo 24).
Replace thermal well
(see page27)
Using a multi-meter se t to the
Ohmssetting, determine the
resistance of thermal well sensor
(see caution photos 23 & 24)
Disconnect thermal
well wire harness
19 20
Replace gas control
(see page 27)
Page 25
Gas Control Testing
See pages 27 & 28 for gas control
input & output testing.
Once the thermal w ell resistance value s are known, the wat er
temperature must also be known to determine if the resistance
values are correct . See page 25 to obta in water temperatu re.
Are thermal well resistance valuescorrect?
CAUTION
DO NOT use standard multimeter probes for this test.
Doing so will damage connector. Use special pin type
electronic probes or small diamet er wire pins inserted
into connector.
IfControl has gone into TCO lockout due to
excessive tank temperature (four flash, 3second
pause) resetcontrol by rotatingknob of temperature
control tothe minimum setting for at least 6seconds
before returning to desired temperature setting.
Observe heater oper ation. If control
continues to lockou t due to
excessive tank temperature,
proceed to thermal well testing to
determine cause.
25