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Valve Problem

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BuzzLOL

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I'm having a problem with the gas valve a generation earlier than the smart valve with no circuit board on top, but maybe a smaller one inside... works for 10 minutes or so then seems to need an hour to 'cool down' before working another 10 minutes... I'm thinking there is a bad connection in that one somewhere's also... there's still 24V at the main valve terminals, but main valve closes after 10 minutes, and get an open circuit inside the gas valve assembly...
 

BuzzLOL

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Thanks, but there's no thermocouple, just a wire to open the pilot valve and a wire to open the main valve... and both have power to them... but the circuit opens up inside the main valve...
 

nealtw

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Thanks, but there's no thermocouple, just a wire to open the pilot valve and a wire to open the main valve... and both have power to them... but the circuit opens up inside the main valve...
Is the polit light not on all the time?
 

BuzzLOL

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Pilot lights about two seconds before the main valve opens and main burners come on...
 

nealtw

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If you canpost a photo of it, one of the tech here can have a look. I think there should be a thermicouple somewhere. If it dosn't register heat it shuts down the gas.
 

frodo

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make and model number would be of great help, picture also
 

BuzzLOL

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2 stage gas valve Honeywell VR8440P... Power from the control board stays on to both the pilot solenoid and the main burner solenoid, but after about 15 minutes the main burner solenoid seems to 'over heat' and goes open circuit... resistance goes to infinity across the main burner terminals... I'm wondering if there is some electronics under the blue terminal block inside the valve body... removing that block of aluminum and looking inside reveals a cavity poured full of hardened fiberglas resin or something around the connections and solenoid... can't tell if the open circuit is a corroded/loose/weak mechanical connection, a circuit breaker, failing full wave bridge rectifier, sensor, or what? After a while with 120V power to the furnace turned off, it works perfectly again for about another 15 minutes, when power restored to the furnace... it's a 24 volt unit, but adding resistors to the wiring shows it works fine down as low as 13-14 volts... and the lower voltage shortens the recovery time till when it will work again after it goes open circuit... the control board doesn't seem to know if the main valve is working, open circuited, or even has the wires connected... of course, once the heat exchanger cools down enough, the furnace turns everything off... but, until then, it's supplying power to the main valve trying to re-open it... anybody know what's inside that resin? ... Almost seems to have similar problems to the newer 'smart' gas valves with failing circuit boards on top of them... which require re-melting the cracked solder connections...

 
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BuzzLOL

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Solved the furnace gas valve problem by replacing the main valve solenoid assembly with one from another identical used gas valve found on eBay for $36... saving the $300 of a new valve and the hours of work to replace it...
 

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