HVAC guys, need help

[Beels]

Got a York Affinity 9.S high efficiency gas furnace. It's been giving me a bit of grief lately. It's trying to cycle on, the exhaust fan cuts in and runs for about 3 seconds and cuts out. The indicator light on it comes on green when it tries to cut in, then turns solid red for 3 seconds after the exhaust fan cuts out. I tried turning the breaker off for a minute or two and back on to reset it and it doesn't help. Pulled the access panel off it and had a look and can't see anything obvious.

Any ideas?

 

[crix]

any flame?

 

[Ex-Member]

There's a thermocouple that needs to be above a certain temperature in order for the gas valve to open. Usually there's a heater or glow-plug type deal to pre-heat that thermocouple to start the flow of gas, once the gas ignites that keeps the thermocouple warm and the valve open until the control circuit closes it, flame extinguishes, and the thermocouple cools off again.

If either the glow plug or thermocouple isn't working, the gas will never flow... that'd be where I'd start. An ohmmeter/voltmeter should be all you need to troubleshoot that.

 

[crix]

exactly where I was going but if the flame is coming in then all saftys/pressure switches are good. then you may need to just clean the flame sensor.

A high efficiency furnace likely wont have a standing pilot or a thermocouple

It should have a hot surface iginition system which will glow red hot just before the gas valve opens.

I would say take the door off and tape the door switch shut and watch exactly what it does crank your thermostat up so its constantly calling for heat if the igintor never heats up and glow, then you have a open safty or pressure switch not operating properly.

 

[Beels]

Thanks for the ideas guys.

I found the manual online and read through it. I had the panels off, held the safety switch, and I can't see any flame through the little window. The burner area is completely sealed off.

Here's the manual
http://www.yorkupg.com/PDFFiles/269434-UUM-A-0407.pdf

It is a hot surface ignition system.

 

[polaris bob]

Did you see that part in the manual that allows you to trouble shoot the blinking light to see what trouble code, if any, is being sent by the computer??

 

[BigAl]

Did you see that part in the manual that allows you to trouble shoot the blinking light to see what trouble code, if any, is being sent by the computer??

What Bob said. Usually the lights will give you an error code. Not sure about the York but some of them had a ignitor that was prone to burn outs. If it's not glowing take the cover off the burner and check it. Usually 1 or 2 screws and it will come out. Careful- the can break real easy. If it looks like it has a small weld spot on it- replace it.

 

[Beels]

Update:

My plumber buddy came over last night and he's not familiar with Yorks, but he was stumped. Seems like some sort of controller issue. The status light was a solid red for 2 seconds showing a control board error (we think). Anyway, I turned the thermostat down, plugged in an electric heater in the bedroom and called it a night. I wake up this morning and the furnace is working again. So I set the thermostat back where I normally keep it and it was working fine when I left for work.

I'm glad it's working, but it's kind of unnerving knowing that it could konk out at any time.

 

[polaris bob]

In doing a quick read thru of your manual on-line I saw where there was a reset button on your control board. Maybe he re-set it when he was checking it out.

If its still working tonight when you get home, look to see if it is showing any codes on the control board.

Other than that, it might be time to call in a service tech to see if its about to poop the bed.

 

[Beels]

Just stopped back at home and it's screwing up again. I checked the fault code storage and it's coming up as 3 flashes - "Normally open pressure switch contact did not close after inducer was energized. This could be caused by a number of problems, faulty inducer, blocked vent pipe, broken pressure switch hose, or faulty pressure switch"

Hoses all look good. Inducer runs, so that isn't an issue. Vent pipe is free and clear. I'm guessing it's the switch. Got a call into the local plumbing and heating guy who's short staffed and swamped, so I don't know when he'll get back to me.

 

[700sks]

possible bird nest in flue pipe?

 

[Beels]

possible bird nest in flue pipe?

No. I checked it and it's clear.

 

[Ex-Member]

Maybe it's bird flu in the nest pipe.

 

[BigAl]

#1-I've had spider webs in the intake pipe cause the pressure switch not to close. #2-Could be the purge blower not coming up to speed. #3-Condensate in the line to the pressure switch. #4-Weak pressure switch.

 

[Beels]

Talked to the HVAC outfit this afternoon. Apparently they're going to try and send someone tomorrow. I'd order the switch and try replacing it, but I'm concerned I might be overlooking something and end up with part / parts I don't need.

I appreciate the help guys!

 

[crix]

Talked to the HVAC outfit this afternoon. Apparently they're going to try and send someone tomorrow. I'd order the switch and try replacing it, but I'm concerned I might be overlooking something and end up with part / parts I don't need.

I appreciate the help guys!

If you have a meter you can check this yourself, put the black lead on the common or (C) on the circuit board screws and the other on the pressure switch if the pressure switch isnt closing it will read 24v on one side and 0 on the other.

before the inducer is started the furnace does a self check to make sure all pressure switches are open, then the furnace powers the inducer blower motor and the force of the blower closes the pressure switch. and completes the 24v circuit. leting the furnace run. but the weird part is the fact its intermitten i would have to look at it personally to check it out its alot eaiser when your in front of it.

 

[Beels]

If you have a meter you can check this yourself, put the black lead on the common or (C) on the circuit board screws and the other on the pressure switch if the pressure switch isnt closing it will read 24v on one side and 0 on the other.

before the inducer is started the furnace does a self check to make sure all pressure switches are open, then the furnace powers the inducer blower motor and the force of the blower closes the pressure switch. and completes the 24v circuit. leting the furnace run. but the weird part is the fact its intermitten i would have to look at it personally to check it out its alot eaiser when your in front of it.

Thanks a bunch for the advice. I have a meter but it's at work. I'll grab it and check it out tommorrow.

 

[Beels]

Well, I shut it off last night before I went to bed. Turned it back on and it works. Still working at noon. I'm completely stumped. Plumber hasn't called me to make arrangements to look at it either.

 

[Beels]

Update:

The local plumber didn't want to look at it because they don't sell York. Ok, fine, I think we had it figured anyway. I bought the pressure switch and held onto it because it has been working fine. Since my last post, it never missed a beat until Monday. I was away and my old man stopped by the house and it quit working again. He plugged in my electric heater and kept it watrm enough in there to keep everything from freezing (it got fairly cold out the last few days). I got home last night around 5:30 and changed the switch out. Hasn't missed a beat since.

 

[pullhardr]

If it does stop again it is possible the intake side of the flue is being subject to back pressure from improper venting outside. If it is going horizontally out it may need turned down 90 degrees.