TESTING THE THERMOCOUPLE AND GAS CONTROL VALVE/THERMOSTAT
IMPORTANT: Before performing any test, check the area around the water heater for any source of a Flammable Vapor (i.e gasoline, paint thinners, etc.) If any sources are found do not proceed until they are removed.
Thermocouple Output Test
The following test will check the DC voltage generated by the thermocouple when the pilot light is lit.
1.Disconnect the thermocouple from the gas control valve/thermostat as shown in the adjacent figure.
2.Using a multimeter with alligator clips leads, attach the red lead to the body (copper part) of the thermocouple. Attach the black lead to the end (silver part) of the thermocouple. Reference the adjacent image for placement of the leads.
3.Follow the lighting instructions on the front of the water heater to light the pilot and watch the voltage readings on the multimeter. NOTE: You will have to hold the button down to keep the pilot lit for the duration of the test. After 45 seconds the meter
should read | Figure 20 |
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IF . . . |
| . . . THEN |
the multimeter voltage reads | • | check the positioning of the thermocouple tip to the pilot flame. If |
at least |
| necessary position the thermocouple to ensure the flame contacts the |
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| thermocouple’s tip. |
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| thermocouple. (See p. 22) |
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the multimeter voltage reads | • | the thermocouple is working properly. Proceed to the gas control valve/ |
more than |
| thermostat test. |
Gas Control Valve/Thermostat Test
(Thermal Switch Models)
The following test will check the gas control valve/ thermostat’s ECO & TCO (Energy Cut Off & Thermal Cut Off). NOTE: This test applies to gas valves with wire leads that attach to the thermal switch on the manifold door.
1.Remove both wire leads from the TCO (thermal cut off switch) and jumper the two leads to complete the circuit. Once the test is complete, remove the jumper and reconnect the wire leads.
2.Follow the lighting instructions on the front of the water heater to light the pilot.
3.Release the knob and check to see if the pilot remains lit.
GAS CONTROL |
|
KNOB |
|
TCO | TCO |
WIRE LEADS | WIRE LEADS |
| (JUMPERED) |
| TCO |
| SWITCH |
Figure 21
IF . . . |
| . . . THEN |
the pilot lights and remains lit | • | the TCO (thermal switch sensor) has tripped OR the TCO is not |
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| working (OPEN). Reattach the wire leads and press the TCO reset |
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| button. Relight the water heater. If the pilot will not remain lit, replace |
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| the TCO. If the pilot does remain lit, the TCO was |
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| due to a lack of combustion air (see pp |
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| of a Flammable Vapor event. Check around the water heater for any |
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| source of flammable vapors (i.e. gasoline, paint thinner, etc.). |
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the pilot will not light or remain | • | replace the gas control valve/thermostat. |
lit with the wire leads jumpered |
| (See p. 24) |
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20