So once the furnace shuts off...it will not restart on its own?
It will if I turn it off at the unit and at the thermostat, which I assume resets it, wait about ten minutes and turn them both back on. Otherwise, the thermstat will read "Heat on" but nothing will be happening.
I am at work and can't look, but if you can provide a link to a diagram or picture, I might be able to tell. Sorry, I meant to take a picture with phone for referance. The only boxes I can recall are made of sheet metal: a small one about 2x3 to the right of the inducer motor that has the pressure switch attached to it and says it has hot wires and to not service without turning power off and the other is behind the lower panel and is about 3x5 and has the control panel and some relays or something in it. I haven't investigated into the inside of either box yet. I was hoping the lower box would have a troubleshooting mechanism in it. My old york Diamond 90 (in another house) furnace had a blinking red light for such purposes. BTW, I dont know what a spark cable looks like either.
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the cable runs from the pilot and is orange.
I will leave this open for you for when you are at the unit
I should be on then...talk to you later.
do you mind a hands on test?
Remove thermostat..take wire from R and wire from W (usually red and white....and twist together...time how long furnace runs before shutting down.
Tell me when it has run longer than normal...or if it doesnt turn off. I am looking to see if it runs without shutting down as it did before.
Once it either stops..OR..you know it has already ran longer than before let me know.
Thank you...and the wires are still twisted together?
And it ran longer than before?
Ok...we are getting there..
When flame shuts off...does the exhaust fan shut off just before, same time or after?
And finally.....the main blower that sends air through the ducts.....it shuts off when?
sorry...but it is important.
format as such:
burners fire up
flames turn off 10 minutes later
exhaust turns off 2 minutes later
main blower turns off 1 minute later
This is sounding like the 3 wire pilot is going bad. The pilot has a warp switch in the side of it. It lights, then it heats up the side warp switch...after a while it warps and connects and sends power to the gas valve for main gas.
I am also suspecting a "domino" theory that the small circuit board behind the pressure switch is affected.
From your last response...you said flame goes out...but what about pilot?
The pilot will need to be replaced first.
This is what is holding the unit pilot mode. Change pilot and let me know.
Keep me posted as you progress.
I have not attached it yet.
I want to make sure what I tell you is worth paying for.
Once we get to a point that I feel I have helped, then I will send link.
Thank you for asking.
Did you say the inducer motor runs after the flame and pilot go out...or at the same time
Now that I am confident the pilot warp switch is sending power, I now need to acess the inducer relay board (behind the pressure switch). The key now is if the pilot and flame go with the draft motor or if the draft motor continues to run after the pilot/flame goes out. Sorry but to find out means babysitting the unit and seeing what happens at shut down.
Small circuit board behind pressure switch controls the inducer motor....is there a chance the motor faults and in a split second the flame goes with it?
Any faulting of the inducer will be because of that small board. Look at the back of board for hot spot.
Ok, thanks. I might not be able to check until tomorrow.
I looked at it last night, but of course I only looked at the front. If I don't see anything on the back, is there a next step?
Not sure about faulting, but motor seems to work ok while running (it puts out a strong exhaust) and I felt it after it shut off and it wasn't overly warm or anything.
This was one of the designs that were tried and stopped real soon after. The small circuit board had a very high failure rate. It can cut the inducer at will...and also not start up unit.
Quite often there is a brown spot on the back of the board. I want you to check first instead of building a new furnace part by part....
At this point we need to see if the main board is dropping signal to the inducer board or if inducer board is dropping signal back to main. Do you have a volt meter?
To save time I am going to format a troubleshoot...terminal to terminal and send. Will pull the schematic and give you a course of action with what to do depending on results.
Coming from the pressure switch are 3 wires...yellow, orange and brown.
Orange is our 24V to the pressure switch from the board. (small one behind pressure switch) We want to put one meter lead to orange and one to ground. We need 24v on the orange all the time after start up. To start 24v connects to yellow....once the pressure switch closes it connects orange to brown.
Once brown gets 24v from the orange at pressure switch it enables pilot.
It does this by connecting through the edge connectors. Pull edge connectors and use a flat piece of sand paper and clean contacts.
If you can clip meter lead to any ground on cabinet and then to the orange wire on pressure switch.
If it faults and there is no 24 v on orange = replace circuit board in blower section or check edge connector.
If 24 v remains on orange replace small circuit board behind pressure switch.
I will continue to leave open for you.
I am very glad it came to an end for you!
Bet you know more about your furnace than you ever thought you would...
Thanks for all your patience with me. I do this between my regular job and home and realize I am not always quick with replies...you showed great character....thank you!