Home Repair Forum

wlc0216 · #11 (**permalink**) 01-02-2007, 10:21 AM

Here is an update. Error code 31 indicated "high pressure switch fault". The switch is located on the gas valve with a six wire plug on top. The switch is fastened to the valve by one screw and at least two rivets making removal impossible. The switch has an adjustment knob on it that has movement limited to 180 degrees and it was positioned in the center of this adjustment range. I checked the wires for good connection and dialed the adjustment all the way to the right and retried the furnace (of course I shut off power to the furnace while working on it). The furnace still had the same problem. I then dialed the adjustment all the way to the left and again retried the furnace. It then began to operate normally and has been ok overnight until nearly noon today.

I dont know how the emergency heat function works. I see it appears to be activated by a switch below the circuit panel. Could someone explain?

PS The links in the message automatically happened when posted, not my doing.

PSS OK now they're gone, whats up?

HayZee518 · #12 (**permalink**) 01-02-2007, 04:40 PM

the underlined links in your script are a function of the forum.

wlc0216 · #13 (**permalink**) 01-04-2007, 03:14 PM

I am back to square one. The furnace has the same symptom as before; the burner ignites and burns for about 20 seconds, the valve makes a clicking sound and puffs of air are heard escaping from around the cover to the burner area and the valve shuts down. This cycle repeats continuously.

I planned to replace the gas valve today but the replacement valve specified by Carrier was not a match. The old valve has a six wire connection collected on a single plug, while the new replacement has a five wire connection with separated 1/4" terminal tabs. I had the parts supplier research to see if Carrier provides an adapter to match up the wiring, but they do not. The old valve is an Essex SX345NSRX-14 which I'm told is obsolete.

In my checking around, I was told that the error code 31 may not indicate "high pressure switch fault" as stated on the unit, but it could also indicate an inducer problem or a problem with the heat exchanger.

Would the emergency heat function provide a short term solution? If so, how is in activated?

Any help would be greatly appreciated!

Bill

Narroc · #14 (**permalink**) 01-07-2007, 01:31 AM

The problem as I see it is no one has been able to see exactually what happens when it faults.
Sequence is: Room Thermostat calls for heat>Induced fan starts>Vacuum (sucky) switch makes >electronic board gets signal that fan is going (there enough suck from the fan)and turns on spark and open gas valve>flame sensor sends signal back to board that flame is established and locks gas valve open>Main fan starts either by fan stat or timer. Heat continues until the room thermostat yells out enough enough .

There is of course a time gap between the induced fan and the flame approx 15 seconds.

So some were along the way it must be faulting. Has water got into the main board? is there a hair crack on the circuit board? Is the flame probe sensor CLEAN. Take it out and clean with fine sand paper. Is the tube from the induced fan to the sucky switch clear? Hasn't got a leak in it?
I had one similar to this last year finally cleaning the flame probe fixed the problem.

HayZee518 · #15 (**permalink**) 01-10-2007, 06:01 AM

there is one post on ebay for the same valve and a robert-shaw equivelant

HayZee518 · #16 (**permalink**) 01-10-2007, 08:08 AM

I drew this diagram of a thermopile - see if it makes sense

chaka454 · #17 (**permalink**) 01-10-2007, 10:43 PM

Hi guys I'm a service technician and your problems sounds very familiar unfortunately without checking the equipment I might not be of much help, but I guess anything helps right..... if the flame comes on and it shuts off after a short time like 10 or 20 seconds check the vent cap, it might be broken, check for an obstruction in the vent, if the cap is broken replace it, one good way of checking if its the vent is taking the cap off at the furnace and run the furnace but not for long you want to be smelling those fumes, this is to check if the flame stays on for longer than 20 seconds like somebody posted, one thing you never, ever want to do and I'm serious about this I've seen accidents happen because of this is to jump out safety switches specially the high limit switch dont ever jump those safetys, they save lives, hope this helps any questions i'll try to help if not I'll find out for you guys, we're a Bryant Diamond dealer so most of the equipment we sell, install, and service is Bryant.

jubrand · #18 (**permalink**) 01-15-2007, 08:44 AM

I have a Bryant plus 90 that's about 10 years old or so too. I've had some of the same problems you guys are talking about. Basically, the burner would fire and burn for about 10 seconds, then shut off. It would try 2 more times before it gave up and locked out for 3 hours.

We originally thought it was the flame sensor, then the gas pressure. None of that seemed to work. FINALLY, the tech (oh sorry, the THIRD different tech), realized that the wiring harness that connects the flame sensor and other burner components (sorry for being basic, I don't know too much about the wiring) was faulty. He replaced the harness, and that fixed it. You might want to check it. In my case, it was just one wire that was pulling out.

Now on to my NEW problem.......For the last week, the furnace can't seem to get the temp up to the setting on the thermostat. the thermostat (Honeywell digital with four time zone settings...wake, leave, return, sleep) will call for heat, and the burner will fire up and burn as it should. But, after about 5 minutes or so, the burner shuts off (blower is always on), even if the proper temp hasn't been reached. The thermostat still looks like it's calling for heat (small flame icon is showing). Sometimes, the burner will fire again, but most of the time it stays off. If I cut the power to the furnace (by opening the front cover to trip the safety switch, or by just flipping the power switch on the side of the furnace), it seems to reset something and upon turning back on, it'll fire the burner again and repeat the same process.

I've got the LED error codes on mine, and it's giving me code 33 after the burner shuts off. That corresponds to "Limit or flame roll-out switch is open".

Does anyone have any ideas??? I'd like to figure it out myself and fix it rather than pouring more $$ into techs coming out. Could it be the thermostat that's broken instead of the furnace?

Any help is extremely appreciated.

HayZee518 · #19 (**permalink**) 01-15-2007, 05:07 PM

connect a jumper across the thermostat and see if anything kicks in. if it does and shuts down after the jumper is removed then you found your culprit.

whacker · #20 (**permalink**) 02-03-2007, 12:35 PM

Hi, original poster here.

Just checking in to say, I've not made any progress since last posting, and winter in Michigan has turned mean!

I've been on some other forums regarding this, and the only suggestions have been to check and make sure the condensate water is draining properly, which if it wasn't would influence the speed of the draft inducer fan, which in turn would influence the operation of the pressure switch. I don't think this is it, but I'm still investigating. I'm still leaning toward changing out the gas valve, but I'd rather not just throw good money after bad.

Hay Zee, I haven't been able to find a way to scan my owner's manual schematic and sequence of operations. If I do you'll be the first to get it.

So in the meantime, I'm relying on a neighbor to come and check the premises daily whenever I have to be gone longer than a day!