In the wall Furnace Repair

[oneplace2u]

I am having problems with the burner not coming on.
The pilot light stays on and is a nice blue color.
I have tested the mv on the line to the thermostat, the mv should be 250 mv when the thermostat is off and 140 mv when it is on. My readings are 223 mv when it is off and 53 mv when it is on.
I have disconnect the thermostat completely and tested and it is 223 mv.
I have taken a paper clip across the connectoin and the burner still does not come on. To me that would tell me the gas valve is bad.
My question is by the manual it should test 250 mv when it is off,
would 223 mv and not the 250 mv make that much of a difference. If that would be the case then my thermocouple is not giving out the right mv and needs to be replaced.

[paul52446m]

I am having problems with the burner not coming on.
The pilot light stays on and is a nice blue color.
I have tested the mv on the line to the thermostat, the mv should be 250 mv when the thermostat is off and 140 mv when it is on. My readings are 223 mv when it is off and 53 mv when it is on.
I have disconnect the thermostat completely and tested and it is 223 mv.
I have taken a paper clip across the connectoin and the burner still does not come on. To me that would tell me the gas valve is bad.
My question is by the manual it should test 250 mv when it is off,
would 223 mv and not the 250 mv make that much of a difference. If that would be the case then my thermocouple is not giving out the right mv and needs to be replaced.

Ok test it this way. disconnect the two th wires from the gas valve, now test from PP to PP, what do you have? Now put the th wire that go to the pp post back on, leave the other th wire off. Now with the stat made calling for heat,
test from the pp post to the the th wire that is still not connected, what did you get? when trying to jump across with th and th wires off , did you jump from thpp to th post.? Does your instruction say you only use a 250 MV power pile? Make sure all connection and wires are clean and tight. You do have MV
thermostat? Then make sure you test it the way i said.
The main thing you have to have is if your gas valve need 140 MV to open then thats what you need after it goes through the stat. This is why it is important to test the right way. How many feet of wire between the gas valve and stat?. Test this and get back with me Paul

[oneplace2u]

I am sorry, what does th and pp stand for?

[paul52446m]

I am sorry, what does th and pp stand for?

are the wire post on you gas valve marked Usually there are 3 post
one is pp, one th, and one ppth. PP is power pile so the two wires from the power pile go to the two pp post. Th is thermostat So the two wires from the stat go to th and th post. You also have to check you wiring diagram The wires that go through the stat also might go through the roll out and limit switch,
you could be losing power through one of these switch.. Paul

[oneplace2u]

Ok, have thtp th tp post.

I will get back to you tomorrow, because the unit is at our church.

I will make the test.

[paul52446m]

Ok, have thtp th tp post.

I will get back to you tomorrow, because the unit is at our church.

I will make the test.

Ok they are calling it a thermopile which is tp or you call it a power pile
which is pp paul

[oneplace2u]

tp to tp 202 mv
tpth to th 202 mv off
tpth to th 46 mv on

It calls for a thermocouple 250 mv

I have about 10 feet ow 16 gage wire connected to the thermostat

[paul52446m]

tp to tp 202 mv
tpth to th 202 mv off
tpth to th 46 mv on

It calls for a thermocouple 250 mv

I have about 10 feet ow 16 gage wire connected to the thermostat

When you checked tpth to th 46 mv on. DID YOU HAVE THE TH WIRE DISCONNECTED FROM THE VALVE??.. Paul

[oneplace2u]

No all the wires were connected

[paul52446m]

No all the wires were connected

Ok testing that way, tells me that you might have a bad gas valve,bad stat,lose or dirty wires, bad limit, bad roll out switch.
You have to test the way i tell you to test or we will not get any where.
I asked you to check wire diagram to see what all was in the th and th circuit.
You did not answer this question. If you take off the th wire, leave the thtp wire connected and leave both tp wires connected. Now with the thermostat
turned all the way up, test from the pp post to the th wire you have off. and tell me what you have.

The next test is, take off both th wires and leave the two tp wires on. With pilot lite use a jumper wire from thpp post to the th post and see if the valve opens, make sure valve is turned on. Paul

[oneplace2u]

I believe I have followed all your instruction
If you take off the th wire, leave the thtp wire connected and leave both tp wires connected. Now with the thermostat.
If I do that the thermostat is only connected on side connected, because it connect to the th and thtp connections. And I gave you that reading. 202 mv
I don't have a real diagram. The user manual does not have one in it. There is any other items in line that I can see. The thermostat is new.
And it is a mv stat.

I want to thank you for your help.
I will turn it over to and expert no. I have failed so it is better to let them do it.