Gas furnance won't turn on

[ZYouL8R]

So we're in the process of selling our house. It's vacant and we live hours away from it, so we're not able to check on it very often. We have a contract on it so the buyer sent an inspector out to do a normal pre-buy inspection. One of the inspector's writeups was that she couldn't get the water heater to relight once she cut the gas to it. So we called someone out, and the tech put "relit pilot" on the comments on the invoice. So I literally have zero faith that this home inspector has a clue what's going on because: 1. She's a woman, and 2. She didn't know how to light a pilot.

So now that the stage is set, we have a new issue. We came up to check out the house one more time before we close and I realize the heater won't turn on. I can turn the fan on from the thermostat, but if I leave it in "auto", nothing happens, even though I have it set for 75* and it is 66* in here. With the fan on, there is no heat coming from the vents. I go up in the attic to see if there are any glaring issues. There is a fault code, blinking #13 (pic below). So for any of you experts, could this have been something screwed up by the inspector fucking with it, or is it unrelated? The unit is only 8 years old so it doesn't have the old style pilot light that you can just relight.

#13


#33


With the panel off.

[2165 Turbo Rail]

i found this on another forum

To determine if it is code 13 or 31. The first digit is the number of short flashes, the second digit is the number of long flashes.

13 is limit circuit lockout, in which case your furnace would try and restart after 3 hours. The limit circuit is there to protect the furnace from overheating if there is insufficient airflow through the heat exchanger taking the heat away from the furnace and pushing it into your ductwork. If this is the code then look for plugged air filters, blocked discharge vents, etc.

31 is the pressure switch didn't close or reopened. This pressure switch is in your furnace to monitor the combustion fan motor to prove you have positive exhaust gas pressure out your exhaust vent and through your combustion chamber. This could be triggered due to plugged intake and/or exhaust piping, defective exhaust blower fan, excessive wind, plugged tubing on the pressure switch, etc. These pressure switches are very sensitive, do not take the hoses off and blow into the switch or you will damage it. I have also seen where an improper grade on the furnace will cause this fault. It should have a slope of about an 1/8 th of an inch from the back to the front of the unit, if not you may build up condensate in the secondary heat exchanger and not get enough flow through the ventor motor.

both of these conditions can be reset by turning off the power to your furnace and then turning it back on. The furnace will then go through its normal start up procedure.

Have a look at your vents outside and make sure that there haven't been any birds taking up residence in your vent pipes, also check your condensate drain ine to make sure it isn't plugged.

[2165 Turbo Rail]

I had this happen to me this year and there is a small brown "box" (1/2 x 1/2 at most) has 2 wires going to it.. there is a push button right between the two wires... I think I found 2 or them in different locations so I pushed that button on both and it worked

[2165 Turbo Rail]

PM sent

if you can't figure it out give me a call and I'll go look at mine and send you pics or something if needed

[2165 Turbo Rail]

The other

[ZYouL8R]

Thanks for the help. I didn't have any tools on me so I went up to Home Depot and bought about $50 worth of shit to try to fix this thing and when I got home, the heater was on. Who knows what the deal was.

[2165 Turbo Rail]

FYI no tools are needed to do what I was suggesting.

Was it about 3 hrs from when you turned it on to when it finally came on? It says that it resets itself after 3 hours

[ZYouL8R]

FYI no tools are needed to do what I was suggesting.

Was it about 3 hrs from when you turned it on to when it finally came on? It says that it resets itself after 3 hours

Yeah, I just bought some test leads to bypass a few of the sensors in question, a voltage tester, and a few other odds and ends. I tried to push in those little buttons or whatever they are on the sensors, but they don't pop in, not the right type.

And yes on the 3 hours, it was probably the reset that did it.

[AdRock]

You could always just replace the limit switches to be safe. I just replaced the circuit board and decided to do the limit switch also. The switch was only $7 at an AC supply place.