Honeywell PDX140S*F(BN,SX,CX) service manual Gas Control Testing, Thermal Well Testing, PDX Series

PDX Series

PDX SERVICE PROCEDURE VI

Gas Control/Thermal Well Testing and

Replacement

Gas Control Testing

See pages 27 & 28 for gas control input & output testing.

Thermal Well Testing

If Control has gone into TCO lockout due to excessive tank temperature (four flash, 3 second pause) reset control by rotating knob of temperature control to the minimum setting for at least 6 seconds before returning to desired temperature setting.

Disconnect thermal

well wire harness

Observe heater operation. If control continues to lockout due to excessive tank temperature, proceed to thermal well testing to determine cause.

Thermal well testing

Position gas control power switch to the “OFF” position and disconnect thermal well harness from gas control.

Using a multi-meter set to the Ohms setting, determine the resistance of thermal well sensor (see caution photos 20 & 21)

20 21

CAUTION

DO NOT use standard multimeter probes for this test. Doing so will damage connector. Use special pin type electronic probes or small diameter wire pins inserted into connector.

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 (see photo 20).

Alternate the probe on the outside position to the opposite outside wire position (see photo 21).

Once the thermal well resistance values are known, the water
temperature must also be known to determine if the resistance	N	Replace thermal well
values are correct. See page 25 to obtain water temperature.
		(see page 27)

Are thermal well resistance values correct?

Y

Replace gas control

(see page 27)

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