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Flame sensor will not come into play until after burners light.If it is dirty burners will light and go back out. Look on control board and tell me if you get an error code Maybe 2 blinks then pause.
Flame sensor not the issue then
Mounted on blower housing.You will have 2 green lights and an amber. Probably a pressure switch problem
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Give me a minute, THis is one of those furnaces they only built for about two year.Lots of issues with the board
Yes I am seeing that. Troubleshooting guide says check for 24v at valve (Between terminals) Do you have a volt meter to do so?
No problem. There should be 2 wires at gas valve.When igniter lights after about 5 seconds check between those terminals.
If no 24v at valve check for 24v across the terminals on the HS780 marked VALV and GND.
If we have 24v at valve (Valve is bad)
If no 24 v at valve check board
If not 24v between VALVE and GN replace board
HERE IS A DIAGRAM SOULD MAKE IT EASIER>
Yes gas supply connects to valve and it is mounted on burner manifold.If you have a pic I can show you where to check
WE should get 24v between yellow and blue wires.
Are you sure you have gas to furnace?
OK you have a bad gas valve. Look on valve and tell me if it is the Honeywell VR8204 or the Robertsahw 7200
OK wait a minute, I did not think any burners were lighting.If one lights you may sill have a bad valve (low pressure coming out) or burners and orifices may just be stopped up.
This is pilot tube. Main burners are fed through 1/2" steel manifold tube.
Does the one burner appear to a be strong flame?
I would start by removing burners and cleaning them.This furnace is about 27 years old. Personally I would recommend having and inspection of heat exchanger done before investing in a gas valve.Life expectancy of these were about 15 years
Gas valve is almost 200 bucks
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