AO Smith Power Vent Failure - Post Mortum and Cause Found

Old 02-09-17, 08:20 PM
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AO Smith Power Vent Failure - Post Mortum and Cause Found

The unit was a 75 gallon tall AO Smith PowerVent Unit.

Symptom: System would start on demand, ignite gas and then promptly go out.
If I rapped on the gas line with a wrench during the startup sequence, the unit would usually start and stay running.
Pressure switch checked - working properly.
Flame Sensor burnished - Same issue.

Had a home warranty, contacted and engaged, they replaced the unit (thank god - less than 2 weeks in home).

Requested plumber to leave gas valve behind for inspection.

Removed unit cover. Condition of circuit board found to be good - no signs of heat distress or damage.
Examined dual solenoids and their connections to the printed circuit board. Noted cold solder joints. Applied light pressure, and both solenoids pulled through the circuit board without damaging the pads.

Diagnosis: Long term heat degradation of the solenoid solder connections, leading to cold solder joints and intermittent operation.

Recommendation on similar symptoms:
Remove power.
Carefully pry cover off gas valve thermostat control.
Inspect solder joints on solenoid, and touch up (remove old solder, use new solder and proper iron, re-make connections)
Reinstall cover (clip on, no screws)
Reconnect power.

Restart unit, check to see if condition has been corrected.
Old 02-10-17, 11:27 AM
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Welcome to the forums.

Thanks for the heads up with your repair.

There are those of us that will do our own "in depth" repair work but as far as a homeowner recommendation...... replaced the gas valve assembly. A gas valve is a very serious and complicated item that only the manufacturer should open.

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