Have a Payne forced air heater. It is about 15 years old. So far, to keep it running I have replaced the circuit board and the inducer motor. Turned the unit off for summer and restarted yesterday. Fan comes on, then inducer motor, but igniter will not ignite. Runs 90 seconds and then shuts off. Tried the test mode and everything works fine including the igniter. Any suggestions?
During its start up sequence does the ignitor glow? Do you get any kind of error code on the board?
In test mode the igniter glows after 20 seconds. In the regular heat run cycle after 30 seconds the igniter gives error code 31.
The Carrier 3-1 diagnostic code indicates that the pressure switch is opening, which means something in the venting system or heat exchanger is plugged up.
Post the model number of the furnace which can be obtained from the rating plate in the burner compartment of the furnace.
The Payne model number is 373 LAU 048115. Have already inspected the vent pipe from the top of the heater forward and it looked fine.
Bypassed the pressure switch thinking it was the problem. The igniter still would not glow. Removed the switch and sucked on the plastic tube connected to the switch and heard a clicking noise indicating the switch was working. Reinstalled and restarted the heater. This time the igniter glowed and the heater starting working. That was yesterday and it is still working. Do I still need to replace the switch?
Sometimes pressure switches will stick during a prolonged shut down once freed will work normally. The fact it stuck once means it could stick again you may or may not be able to get the furnace up running. I'd get a new switch keep it on hand just in case.
Grady and I will have to disagree here.
In my experience, pressure switches are rarely need to be replaced ---perhaps 2% of the time.
The problem is almost always a defect in the heat exchanger, drainage or venting system of the furnace.
I've never seen a stuck pressure switch myself. What I've seen are furnaces that have barely adequate pressure to close the pressure switch, which causes the pressure switch to operate erratically and unreliably.
In such marginal conditions, tinkering with the pressure switch might cause the furnace to run --- temporarily. But in minutes, hours or days it will be failing again, and it will continue to fail with a new pressure switch until the actual problem is diagnosed and corrected.
Too many repair service make a science out of pressure switches: pointing out to customers that the pressure switch is shutting off the furnace and charging a fancy price to replace a perfectly good switch. Then charging for another service call or two until the aim of the exercise is achieved and the new customer is sold a new furnace he doesn't need to go along with the new pressure switch he didn't need.
The CORRECT means to diagnose why a pressure switch is opening is to connect a suitable manometer to measure the pressure that the manometer is sampling. About the only time a pressure switch should be replaced is when the pressure being measured is normal but the pressure switch doesn't open.
Unfortunately, all too few repairman make that basic test.
I will have to agree that pressure switches are most often replaced needlessly the problem is elsewhere but they, albiet rarely, fail. They are an air or vacuum operated electrical switch having a diaphram to make or break the switch. Sometimes the diaphram gets stiff or the contacts get fouled or worn. I've actually tapped on pressure switches had them operate. Another common problem is corrosion in the barb adaptor (particularly with metal housed switches) which is easily removed with a drill bit.
With all due respect to S/P, I guess we'll just have to agree to disagree on this one.
Hello Grady,
Nothing wrong with a little professional disagreement!
I would suggest that the correct way to diagnose the problem when a pressure switch is found open is to use a manometer to check the pressure being applied to the pressure switch. If the pressure is good and the pressure switch failed to close --- you can replace the pressure switch with confidence that it's the problem.
(of course something upstream of the test point could be an issue too).
If you check the pressure and it's marginal --- then I'd ignore the pressure switch in favor of checking the furnace system to identify and correct the problem causing the marginal condition.
Once that has been corrected, I'd cycle the furnace a few times to see if the pressure switch was then operating reliably. If it was, I wouldn't replace it.
I maintain that the information that is essential to diagnosing the reason a pressure switch isn't closing is measuring the pressure being applied to the pressure switch. Yet relatively few repairman bother to make that check.
Using this methodology, I really didn't have to tinker with pressure switches. I could usually correct the problem accurately the first time out. And you know when you've corrected a problem with the vent, drain or heat exchanger --- you aren't correcting one problem and overlooking another.
SP,
Agreed 100%. The biggest problem I've encountered over the years is finding the specs on the pressure switch for various pieces of equipment, especially after hours. It seems manufacturers enjoy making such information difficult to find. Often my supply houses don't even have such specs handy have to call the manufacturer. If I had the spec I could use an adjustable or fabricate a bracket for mounting. Sorry 'bout the rant. It's been one of 'those days'.
Hello Grady,
I used to keep a notebook of pressure reads I took on different furnaces. And just taking reads often enough gives you a good idea of when a pressure is good and when it isn't.
The pressure the switch opens and closes really ought to be listed either on the pressure switch itself, or better yet on the rating plate.
That would make things too easy though, I suppose.
I'm not about to get between you two, however, my experience has been spider nest in the pressure switch. Easily cleaned with a paper clip. Actually clean both fittings at the tubing ends.
MBK3, I've never seen a spider nest in a pressure switch port but why not? They'll nest in a burner orifice. Good tip, thanks.
I wonder did you resolve the problem? I have a payne furnace 90, found out the problem of the drain get plugged up that caused furnace to shut off all the time. SO try unplug the drain and clean it.
Tags: payne, heater, pressure switch, pressure switches, when pressure, with pressure, heat exchanger, pressure being, that pressure, with pressure switch, after seconds, applied pressure, applied pressure switch, being applied
