I have been looking over the forums the past couple of days and have tried some things....
Here is the problem, The furnace goes on, the big house blower starts up, 45 seconds or so the the small blower in the furnace starts up, then the glow plug lights up, the flame ignites, and it runs for 2-3 hrs. Then I notice cold air coming through my vents, go check the furnace and the flame is out but the furnace is still blowing air. I look at the thermostat and the house is not up to temperature yet. The code blinking is 13, I thought that the problem could be the limit sensor so I replaced that last night. I had the same problem this morning when the heat came on in the morning. To get the heat back on i can hit the manual reset button, turn off the power to the furnace, and then turn it back on. Everything will work right and turn off the way it should if it doesn't have to run for a long period of time (hits the temp it should on the thermostat). I sometimes get a code of 33 but after I reset everything it goes away as well. The air conditioning on the unit works perfectly fine, just the heat thats the problem.
Things I have checked:
New filter
furnace exhaust to the outside(blowing air out, not a lot but can feel it coming out. don't know how much should be coming out.)
limit sensor (new one)
the flame is blue, no yellow or any other color
the returns are all free of constriction or being blocked

Any help would be much appreciated.

Thanks, Chris

 

What is code 13 and 33? Does it have a code chart on the furnace panel? If not what is the model number?

 

I guess i was wrong about if it runs for a little time to reach the target temp it would work fine, it doesn't. I looked at the temp on the thermostat and it was a degree above target which usually means the furnace will turn off. Went downstairs to check the furnace and it was still blowing without the flame lit and the code 13 blinking. I just turned of power without manually reseting and turn back on and the 33 code was now blinking. i then manually reset, powered off the unit, powered on the unit, and all codes were erased and is ready to go on again when the thermostat triggers it.
Any Thoughts?

 

code 13: limit circuit lockout
code 33: limit circuit fault
model number is carrier cnrvp2417acaabaa I believe.

 

I can't get any thing on that model number. The number should be inside the burner compartment.

 

How about pg9mab036060aasa

 

Sorry, nothing on that number either. There could 4 or 5 limits in the furnace so without a wiring diagram it would be tough to troubleshoot. If you could post some pics of the wiring diagram and of the furnace that would help.

 

I guess it is a payne furnace, the model number is pg9mab. The top part above the actual furnace unit is carrier.

 

http://dms.hvacpartners.com/docs/100...SG-PG9M-06.pdf

http://www.managemylife.com/mmh/lis_...L/L0521042.pdf

 

Yes that is the one.

Thanks for the help

 

Thanks Firedawg! OK, the only manual reset is the flame roll out switch. First thing I would check is restriction in the vent pipes or weak combustion blower.

 

Checked the restriction vent pipe and that seemed clear, how do I check if the combustion blower is weak? when it runs it seems like its running the way the combustion blower should be running. Any other suggestions?

Thanks again

 

I guess the problem is the secondary heat exchanger, it was making the combustion chamber way too hot, not allowing the heat to get out, and thus setting off the limit switch. The co2 readings coming from the exhaust were also really high, which is also a sign of a bad exchanger. Its covered under warranty, just have to wait a week for install. Thanks for the help.

 

Where I stay for the past year the furnace shuts down from time to time. We had to flip the furnace switch off and on and it would most of the time ignite. Sometimes we'd have to throw the switch several times to get it on. The owner insisted it was the flame sensor. (I find a flame sensor either works or it doesn't, it's not sporadic but it's not my furnace so...) finally she bought one, I installed it this morning, the problem has become a several times a day issue, this had no affect on the problem. I went ahead and took out the burners and blew them out, they were loaded with chunks of dust that had built up over the years. I did not do this to begin with because the owner stated she just had it serviced and cleaned, obviously she had been taken. The flame is obviously stronger now and the unit lights every time. So I say if your furnace ignites sporadically, it's most likely not the flame sensor, if that flame is not hot enough it's going to shut down on 13, and lock out 33 for three hrs. The burners have a narrowing orifice and have to be blown back to get the dust out. The easiest way is to remove them, there is not much space between the burner end and heat exchanger.

 

Welcome to the forums.

The 13/33 codes are heat related. Nothing to do with the flame sensor. However, the flame sensor is a metal rod that sits in the flame and becomes covered in a glasslike coating that insulates it and causes intermittent problems. That rod should be cleaned with a scotchbrite pad every year.

The most common cause of a limit trip is airflow thru the furnace. A dirty filter, clogged A/C coil, blocked returns, too many closed down registers, dirty blower wheel, intermittent/slow blower are all causes of the problem.

 

Hello Rhead62,

Unfortunately, your recent post is a model of DIY furnace repair. You are making a series of guesses and repairs you suppose will fix the problem. When it doesn't you go on to another guess and repeat the pattern.

You really need a more scientific approach that begins with an understanding of the series of events which occur when the furnace lights up normally and careful observation of what is actually happening with your furnace. That allows you to identify at what stage a problem occurs.

Then think of the variety of things which can cause that symptom and think of the various ways you can test your furnace to see which one might or might not be the cause of your problem.

Being able to follow this process is much of what furnace repairman get paid for. All too many aren't especially good at doing it themselves.

PJ Max's posts consistently help point DIYers towards that scientific method of identifying furnace problems.

 

Is this not what this forum is about? DIY? I'm not a furnace repairman, I don't have a truck with parts. I do have experience in dealing with many things. I do understand now on this carrier furnace the combustion chamber is open, that is it sucks unfiltered air through the burner funnels where dust, pet hair etc can accumulate into the orifices where the gas passes through and is mixed with air just before ignition. This was my problem, it was intermittent, sometimes our furnace operated, sometimes it did not. Perhaps the coating on the flame sensor could cause a intermittent problem but if after cleaning that i suggest cleaning the burner orifices. As my furnace was operating the flame looked fine but after cleaning the burners i noted a difference. Now if someone is on a diy forum and wanting a suggestion on this problem i suggest; clean your flame sensor, then remove your burners and blow them out while your there, it's minimal work (30mins) and costs nothing!

As a result for the first time in a year our furnace has operated for 48 hrs without one shutdown

The owner had a repairman out to look at this over 1 year ago. He replaced the flame sensor. Charged over $150 to clean and f o repairs. Obviously the burners were not removed and blown out as when I did this chunks of dust came out, or to be more scientific for you, upon blowing out the burners large particles were witnessed flowing from the opposing ends of each burner funnel. When finding this problem I consulted this forum. It lead me to these findings I hope it can be of help to a fellow diyer or maybe a few technicians.

 

4 days now, not one shut down, I have developed a scientific theory;

Unfortunately technicians come out, want to get through a call as quick as possible. They drag out multimeters, fudle around, someone found rubbing a flame sensor with sand paper makes it more sensitive and the system operates briefly, long enough for the home owner to get out the check book and pay them. They leave, very soon the problem crops up again and the home owner is fustrated. It's a little work, remove six scews, remove three burners and clean them properly, reinstall. Now after exhausting this simple procedure I'm all about moving onto more complicated processes but perhaps that should be left to the professionals and not a DIYer. Sometimes the simplest procedures get overlooked by professionals because they need science to tell them.

 

The 13/33 code is an overheat problem. It's not caused by dirty burners. A dirty burner issue would be poor lighting.... burners not lighting quick enough or completely. If it was a weak burner problem that could cause the flame sensor to not operate properly causing a shutdown but it would be a different code.

Glad you got it working. Here's the thing.... a gas furnace should be cleaned every year. Many people don't think to have the furnace cleaned until years go by and it stops working correctly.

 

Fault Code 13
LIMIT SWITCH LOCKOUT—This fault indicates the limit switch has tripped 10 times in a row in high fire or 3
times in a row in LOW FIRE during a call for heat. Control will auto-reset in 3 hr.

NOTE: After 2 low-fire limit trips, the control is locked into high-heat mode; however, a third low-heat cycle can be forced due to excessive restriction in air delivery system.

My system would try to ignite three times then lock out for three hours.

This is from the manual and that does say low fire.

 

Here is the thing

If you want to sound like you know it all, you should first read the text of the fault code. That way you won't look foolish in the end.

 

I feel I need to apologize to pjmax, sorry I'm actully pissed off at seattlepioneer, who's comment's to me hold no value in a forum like this. There only meant to be decisive, offer absolutely no information on the subject. I think if people are open minded they never stop learning, even an expert. I am a jack of all trades, I've seen a lot and in a wide range of trades. I'll never stop listening. I love a good conversation and for the most part the posts on this are helpful, especially pjmax's, I would have to say I would defer to you as an expert on heating, except for this instance; 13 code fault on a carrier. My unit was shutting down and flashing 13, it would ignite three times in succession then shut down. That is a low fire fault. I think I'm done ranting, time to move on.

 

Last summer, to help with allergies, we replaced all our filters (4 returns 12x12 and the 14x20 HVAC) with high MERV Filters. Worked great all summer. But then this winter the furnace began setting 13/33 codes. Replaced the high MERV Filters with MERV 1 and the codes have all stopped.

Note: Troubleshot the circuit. Verified 24VAC in and out of each switch. All worked proper. Issue was overheating due to restricted airflow caused by high MERV filters.