Guardian PowerVent Training Manual SVC900; Rev 1
Page 23
Verify temperature calibration: Measure the resistance value of the thermistor by measuring
between the two white wires of the red Molex connect. Make sure the connector is not attached
to the control module or you will get a false reading.
Verify thermistor is good with an Ohms resistance test. At room temperature, resistance is
approximately 10.4 k Ohms (10,400 Ohms S).
1. Remove the red Molex plug. Measure the Ohms resistance value between the two white wires
on the plug.
2. If there is no resistance at all, then replace the gas control valve.
3. If there is any resistance, then the thermistor is probably OK. The actual resistance during this
Ohms check will be determined by the temperature of the water. If you introduce cold water into
the tank, you will see a change in the resistance.
Figure 7 – Thermistor and ECO Check
HOW TO CHECK THE ECO (ENERGY CUT-OFF)
The ECO is a one time use safety device that trips at 200°F. Verify ECO is good by doing a
continuity check between the two red wires at the red Molex connector. Continuity means the
one time use ECO is not tripped. Lack of continuity means the one time use ECO is tripped.
Replace the control valve. Remove the red Molex connector before conducting the continuity
test.
1. Remove the red Molex plug. Measure the continuity between the two red wires on the plug.
2. If there is no continuity at all, then replace the gas control valve.
3. If there is continuity, then the ECO is OK.
HOW TO CHECK THE GAS CONTROL VALVE
Pilot Side of Gas Valve - Ignition attempt by the control board means you should be hearing the
spark ignitor along the orange wire. Check to make sure the valve is
turned ON. At the same time, 120V opens pilot vein of gas valve.
You will have 120V at the yellow #7 pilot valve wire. If you have
120V and there is gas vacuum, then you must have a pilot flame. If
not replace the control valve. The "trial for ignition" will last for 75
seconds. The unit will try 3 times total for ignition, it will initiate a
post-purge (30 seconds) to clear the combustion chamber, and then
go into lockout. LED indicator will flash 1/1 times.
Figure 8 – FV Wiper Gas Control
Main Valve Side of Gas Valve - After pilot flame has been recognized (rectified), the spark will
stop and main valve is energized. Check to make sure the valve is turned ON and you have a
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