York furnace possible problem

[gcompc]

Hello all,
I have a York furnace that is about 6 years old and has been running fine. This year it has started acting very strange. Early in the year It started shutting down and giving 4 flashes for an error code. Info I have states that this is a open high limit switch. I checked and replaced the filter, made sure the blower fan, venter motor were ok, I checked the pressure switch by disconnecting it and got the 2 flash error code immediately I reattached the hose and the 2 flash code went away. I replaced the high limit switch.

After replacing the high limit switch the furnace ran fine for a couple of days then would shut down giving a 5 flash code which is a open rollout switch error. This will happen intermittently, the furnace will start up and sometimes run for 2 to 3 minutes and shutdown with the error code. Sometimes it will start and shut down immediately with the error code. I checked all the roll out switches for continuity and reset, all seem to be good. The other part is sometimes the furnance will function normally for 2 to 3 days with no problem then this error will occur, it really dosen't matter if it's an extra cold night or just a cool winter day.

I replaced all 6 of the rollout switches and removed and inspected around the faceplate in the burner area and looked for signs of flame intrusion or cracks , found nothing. I've also cleaned the burners and replaced the flame probe. As I type this it is giving the error code and shutting down again, sometimes if I wait for 5 minutes and try it maybe after the 4th or 5th try it will run normally for a day or two then does it's thing again.

I've also checked the flu for blockage, nothing there. This sucks I'm paying a$278.00 utility bill and freezing. I don't have much left to replace except the bastard control board, hope that's not the problem, the model number is PKBM-LD20N120C, any ideas? thanks if you do.

[hvacwiz]

I dought if its the control board, Is this a 80% or 90% furnace? If it is a 90% you could possibly have a restricted secondary heat exchanger. How does the flame look when its burning?

[gcompc]

It's a 80%, I also forgot to mention that the extractor motor keeps blowing through all of this. I also replaced the flame sensor not a probe. Today it's running beautifully again for no apparent reason I haven't changed anything. How can I determine if there's a restriction? thanks

[hvacwiz]

well if this is a 80% furnace then it is not a condensing furnace, therefore you dont have a secondary heat exchanger that is restricted. How does the flame look when running. If your at times tripping flame rollout switches there has to be a reason why. Is your furnace located in an area with enough fresh air or in a small closet. A lot of factors come into play with a situation like yours that are hard to solve over an forum, hate to tell you but you might just have to call somebody to come take a look at it. good luck

[gcompc]

The flames are blue with very little if any yellowing. It stopped working properly again most of the day. Reset it several times now it's running normally again. Another thing is if it was tripping the rollout switches I should have to reset them as they are the mechanical type, but I don't, it will start up and run normally after several resets. I think you're right I will have someone to come and take a look, I'm out of ideas, thanks for the suggestions. I'll post what they find.

[mike n]

Are all the rollout switches manual reset and when it fails now does it give the rollout failure code.
When the furnace is on burners on and the indoor fan comes on does the flame move around sputter and come out of the heat exchanger area and into the area of the manifold this unfortunately would indicate a failed heat exchanger.

[gcompc]

I haven't called anyone for service yet as this is a puzzler and I want to try to solve it before I give up.

The flames are blue, steady with minimal yellow flicker. The furnace recieves plenty of ventilation, it's in a basement washroom which has an air vent in the wall. When the blower comes on the flames don't change just stay a steady blue. The rollout switches are manual but don't have to be reset when it starts up and runs normally. The rollout switches are all replaced and are new. It does give the 5 flash error code. The error will sometimes occur immediately right after I apply power well within 1 second, before the furnace even starts up. I don't see how it has time to sense anything at that point. Flipping the power off then back on it may error out 6 t0 10 times then start normally and run fine for a few days then may not work correctly for 2 days.

Another thing of note, I always here what sounds like a relay opening on the control board before the error occurs and the furnace shuts down. Don't know if this is normal or not because maybe if the furnace does since a problem the relay is supposed to open or could it be faulty? I don't know.

[mike n]

On the initial call for heat before the indoor blower comes on if you are watching the flame as the blower comes on does the flame move around any or come out (rollout) of the heat exchanger area, if not I would look for a bad ground by removing and replacing every ground wire on the furnace if the flame is moving around when the fan comes on you probably have a bad heat exchanger

[gcompc]

When the indoor blower comes on the flame is steady and blue, no flicker or sputter. I've also removed the faceplate in the flame area to look for soot etc. it looks ok as well. When the flame come on it's solid. Like I was saying lots of times the error condition will happen the second I turn the power on, the extractor fan will start and the error code will flash this is within a half second or so, other times I will cycle it several times until it starts normally.

I think the open to ground may be possibilty. I'm thinking about removing the control board cleaning every connection on it, checking and cleaning all wire connections in general. I don't think I have a T-Stat problem although I'm not sure of that either. I'll do all this this weekend while there's some heat in the house. Any other suggestions? Thanks

[gcompc]

It's been s long chase but finally got problem resolved. Removed control board cleaned all terminals reinstalled, Nope! same thing. Finally after looking at some other problems on the forum I realized that I had not disconnected the thermostat jumpered the R and W terminals. That did the trick! furnace runs normally. Off to the Home Depot to purchase a new thermostat. I was that close to replacing the control board. Thanks to everyone for the help.