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At any time do you get 24v on the wire to gas valve from roll out switch?
sorry had to clean sat dish off (snow)
You will put one meter lead to blue wire on valve and other to ground.
See if valve gets 3 seconds of 24v after ignitor glows aprox 20 seconds
power on, gas valve on
leave wires attached
thank you....this means you have a bad circuit board. It sends al signals except the final 24v to the valve. This is a circuit board defect.
No fix except to replace the circuit board
that is what we were checking at the valve after the ignitor glow.
You have 2 choices:
24v goes to valve for 3 seconds during ignitor glow but no gas = bad gas valve.
NO 24v to gas valve during ignitor glow = bad board.
It is either board or valve.
The 24v test tells us which.
you should be testing the wire that goes to valve from roll out...not the wire that goes back to board
gas valve has 2 wires..one comes from roll out....the other wire runs back to circuit board...the wire back to board is common and will not read voltage
I know....that is why I said test the wire from roll out to gas valve....the other wire (thats 2 all together) goes back to board. The GMPN is a basic single stage gas valve.
You should be able to tell if valve gets 24v no different that how a light bulb gets 120v
my schematic shows blue as the 24 in from rollout.
But that is also why I say wire from roll out.
You can also remove both wires and hook one wire to one meter lead and the other wire to remaining meter lead.
but they have to be off the valve this way
this will boil down to the 24v present or not...24v present = bad valve
no 24v = bad board
what setting is on your meter or can you post pic?
set for 200 and test a working outlet. verify 120v....then leave set for 200 and test valve
yes...I was testing meter...if it reads 120v for a supply voltage...then it should read a full 24-28v for gas valve.
if you are testing while ignitor glows...then r to w is not needed. R to W is is the furnace doesnt start at all...you have exhaust fan, glow etc...so thermostat works.
If you test the gas valve the entire time the ignitor glows until it goes out...And...
no 24v reading happens = board
24v happens is bad valve
you are getting a flame fail code..not a roll out or limit code.
BUT....all you would do is work backward following that wire....looking for 24v.
No different than looking for power to an outlet. If not at one point back track to next...or start where you know you have 24v...like the first roll out or limit. The schematic on the blower door shows the path
we care about voltage more than ohming coils at this point. find yur 24v...and go from there...
Ready to try some more?
Looks like Billy has opened question up for other experts.First of all take a look at this diagram and tell me if wires and colors match what you have .
Good evening Steve. If you are getting 27v at gas valve, either the gas valve is defective or you have a gas pressure issue.To determine which, attach a manometer or gas pressure gauge that reads inches of water column to inlet and out sides of valve.
If you had an open limit the led would blink 4 times pause , 4 times pause until limit is closed.
If limit was open we would not get igniter.If rollout switches were open we would not get the 27v to valve.
OK with ignitor glowing do we get the 24 to 28 v to gas valve?
OK if all other gas appliances are working, most likely a bad gas valve.If we are getting 27v to valve there are no limits,pressure switch or rollouts that are not doing what they should.If any of these were an issue, the board would not send 27v to valve. The solenoid sounds like it is clicking but gas valve not opening.Replace valve and this should solve your problem
At this point of furnace sequence valve should be open.To question any other component such as a limit or a pressure switch would be like a car engine not starting and wondering if low tire could be the issue.
Absolutely.You can wait until we are finished to rate answer.
forward to hearing back.You have a great evening too.