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Old 12-15-2009, 10:10 AM   #1
12 year IBEW member
Join Date: Jan 2008
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Gas valve on a bryant

Back round info, Tried to start the furnace with no luck at all, opened up the unit and found the control board and the wiring harness on the unit were burned up( harness where it plugged into the control board). Thinking that one caused the other, but not sure which one was first. I replaced both board and wiring harness with new units and tried to turn on the furnace, with this progression, Call for heat,induction fan kicks in, ignition module fires,piliot light ignites but the main burner never kicks in.I have done some trouble shooting on the unit it has a three wire switch attached to the piliot lite asssembly that has a normally open and a normally closed metalic switch on it.The feed for the switch comes from term 4 on the gas valve which is piggy backed to to wire coming from secondary control board located with the presure switch and induction motor relay. the normally closed side of the three wire switch goes to term 5 on the gas valve and on to the ignition module, the normally open side of the switch goes to term 1 on the gas valve and also back down to the main control board.I have a wire from the main control board that goes from term 3 then term 5 on the valve then onto the other side of the ignition module.I've been told that the switch is to heat with the ignition and change positions opening power to the term 5 on the valve and the ignition module, at the same time closing switch to term 1 on the valve and back to control board. not sure if this was working so I put in jumper between the term 4 and term 1 to mimic the closing of the switch and still nothing.Wondering what voltage should be at terms on valve before and after ignition. thinking I have a bad valve????Sorry this was so long but wanted to get as much info out there right away to save time on followup questions.

Furnace specs:
Furnace bryant model #398aawo481ood
gas valve 646ax-1

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Old 12-16-2009, 08:42 AM   #2
12 year IBEW member
Join Date: Jan 2008
Posts: 29

Gas valve on a bryant


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