Hello, On Wednesday the furnace stopped heating (Bryant 90plus model 340MAV) . Checked error code. It said reset flame rollout switch. I did. Furnace worked fine for 2 days, then the same thing happened. I then replaced flame rollout switch with a new one. Furnace worked fine for 1 day, then it happened again. It has a new furnace filter in it and everything else appears to be operating fine. Any suggestions what to check next??

(I can keep it running by using a small fan to keep the area by the flame rollout switch a bit cooler, but I know there must be something wrong... )

Are all the vents open,, supply and returns, Nothing blocking or covering them ,something is causing it to over heat,, can you check the main blower with a amp probe to see if its pulling the correct amount of amps and not to many. The fan could be running to slow

Thanks... nothing is blocked (supply / returns) and all vents are open. I will try to borrow an amp probe tomorrow, but main blower air volume feels the same as before...

(The furnace filter was filthy/plugged.. guess I forgot, but I replaced it Weds)

It does seem that the area where the sight glass is (heat exchanger / combustion chamber?) is extra warm... not sure if it is or why it is...

You need to check your vent (the pvcflue) for blockage. Also if it isn't sloped toward the furnace water could be building up in the exhaust.

No blockage found. No problem with draw from blower fan. Combustion chamber area is getting very hot (by rollout switch)... Could it be a blocked / plugged heat exchanger??

The first thing I would check in this situation is the gas pressures. However, it is best to have this professionally done. If manifold pressure is to high, it will trip the rollout switch. Also, yes plugged heat exchanger can cause this, but you should be able to see the flames actually rolling out if this was the case. Cracked heat exchanger can also cause this problem, so I really think its time to get a pro in there to check your system. Good luck and please let us know what they find.

My Carrier gas furnace has a similar problem but I was able to keep the furnace running my placing a wire jumper across the flame roll out switch. Can is problem be traced to the computer board, perhaps the 3A fuse which I haven't yet checked

My Carrier gas furnace has a similar problem but I was able to keep the furnace running my placing a wire jumper across the flame roll out switch. Can is problem be traced to the computer board, perhaps the 3A fuse which I haven't yet checked


You need to make sure you have very good fire insurance, and even then when the fire marshall finds someone has jumpered a very important safety device in the furnave,, they just might no pay for the new home you will be needing

Blocked / clogged heat exchanger is the diagnosis (from 2 reputable fuirnace companies). There is a bulletin about my furnace... guess it's a common problem. These older Bryantc 90plus's are junk I guess!! Putting in a brand new Rheem 95plus 2 stage with modulating fan furnace today.

Thanks for the help!

PS - NEVER bypass the rollout switch... you are asking for trouble!!

Pj, I think you made the right call going with a new furnace, hope you enjoy it and you get years of trouble free operation.

THANKS! New furnace is running great so far today. I'm just a bit scared of the "new technology"... hope it's problem free!

Yep, technology has come a long way in furnaces in the last decade. I also hope its problem free, but with anything new these days, you just never know. The most important thing about having a new furnace installed, is knowing that it was installed by a company that will stand behind the product they sell. This way, if the unit has a glitch, you can be rest assured the installer will be there as quick as possible to remedy the problem. Ive had extremely good luck with rheems(very few callbacks). Once again, enjoy your new purchase.