bad valve?

[jmanwoodie]

I am checking into a furnace that is giving me some trouble. The furnace goes through its sequence, ignitor comes on...gas valve clicks and a fracction of a second later it clicks off as well as the ignitor. It trys 3 times and then goes on system lock out.

I pulled the two wires off from the gas valve and it does the same thing.

The ignition module is new.

What else should I check?

[Dad]

1.Ground
2.Flame Rectification
3.Proper AC polarity


http://www.heatincorporated.com/~tec...g/Flamerec.pdf

[blk]

More info needed, make and model, nat. gas or L.P. Is there gas to the unit?

[mike3]

Brand of furnace and age

[filterchanger]

Check the gas pressure

[jmanwoodie]

this furnace is a York...maybe 7 years old...i've checked polarity and ground...the time the valve is on is not long enough to get to flame rectification...

furnace is natural gas...gas pressure has not been checked...with the wires pulled from the gas valve would pressure still be a factor?

I ohmed the valve coil... .098 K ohms...

I checked voltage at the valve...the voltage starts out high, like a 100 or so, then drops right to 24 volts...

[blk]

Possible faulty ignitor , check cold resistance of ignitor and compare to unit specs.

[jmanwoodie]

i disconnect the ignitor and it still does it...

[mike3]

Do you trust your meter? 100 volts in 24 volt system ??
Heat anticipator if one present. Pressure switch/fittings clear?

[billva]

Wow

[indianroadmaster]

just a thought possibly a restriction in the gas valve. some junk on the screen/or on the orifice - is not letting gas through. 100 volts on the 24 volt side is not correct. your meter is not set right or is broken. the amount of time the valve is open and not get flame rectification might be the precise problem. the sense rod is dirty therefore no rectification. old wise man said , dirt is death. gotta be something simple.

[Toolpusher]

How can this be a flame rectification problem if theres no flame to detect ?

Atleast I didn't read that any flame was present. He said the valve clicks (has voltage) then clicks again (no voltage) Hence no flame.

The way I read this post is that the ignitor lights, valve energizes, then shuts down.

T-stat anticipator comes to mind.
I think Mike is on the right track,

It is possible that the coil in the valve is bad and won't stay energized.

[jmanwoodie]

yes..yes...I like the heat anticipator idea...thank you...I will check that out tomorrow.