# Troubleshooting Gas Furnace



## yuri (Nov 29, 2008)

Your limit control is shot. sits behind the gas valve and above the burners and circled in green


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## Jesper (Feb 27, 2014)

Thanks for the quick reply. Sorry, I did replace the limit control switch.
Part #HH12ZA176A L170-40F

Also, the control board is new as well... ICM281 Carrier Bryant CESO110057 Control Circuit Board
Picture of Control Board = i58.tinypic.com/14m8g3a.jpg

Here is a close-up of that area.
Picture = i58.tinypic.com/1zr2jbq.jpg

I did buy a multi-meter, not an expensive clamp one, just one of those $20 ones I picked up at Lowes. So if you want me to try to check any connections for proper amperage please let me know.


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## yuri (Nov 29, 2008)

on the wires to that limit control is a red diode fusible link. check if it is open with your ohmeter. you should have no voltage across the 2 wires of the limit control when you turn on the tstat and have it call for heat. if you have 24 volts across it then it is open or you got some faulty wire connection on it or to the circuit board. usually when that limit is open the board runs the main fan continuos as it thinks the furnace is overheated. you may have a faulty board. hope you bought a brand new one not some junk from ee-bayy.


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## Jesper (Feb 27, 2014)

My wires to the limit control switch don't have a red diode fusible link.
One leads from there down to the control board, the other leads to the flame roll-out switch.
Picture of the two red ends going to my limit control switch = i61.tinypic.com/117e0wp.jpg

Found this picture on Google of what you're talking about I think... but none of my wire leads look like that.
Picture = i59.tinypic.com/fjdcvr.jpg

Testing (to make sure I did it right)
Black to COM
Red to V ohms mA
Set to measure 200 V~
Turned the tstat on and called for heat
Put red pobe to one connection and the black probe to the other connection.
Reading was 0.00


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## Jesper (Feb 27, 2014)

Ok, sorry Yuri. I kind of feel like an idiot now, but I think I am reading the error code wrong. It blinks 3 times fast and 1 time slow.. so I think the error code is really 31?

I see low voltage inducer is in that error code...

The control board was bought on Amazon amazon.com/gp/product/B004I5FD4G/ref=oh_details_o00_s00_i00?ie=UTF8&psc=1
Limit control switch I bought at midwestapplianceparts.com - they have a lot of parts, but terrible customer service.


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## Jesper (Feb 27, 2014)

I checked the voltage on the inducer, good news is I got a 124 volt reading on it. Bad news is I still don't know why my furnace won't start. I'm thinking maybe it's a pressure switch problem now?


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## yuri (Nov 29, 2008)

first digit is the number of short flashes and second digit is the long flashes. read the sticker on the back of the door carefully and it will tell you that or the info with the board.


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## Jesper (Feb 27, 2014)

Yes, the error code is 31. 3 short flashes and then a long flash.

Error 31:
-Proper vent sizing and condensate pitch or sag.
-Defective inducer motor or start compacitor.
-Vent restriction or high winds.
-Defective pressure switch or connection. If it opens after trial for ignition period, blower will come on for 90 seconds recycle delay.
-Inadequate combustion air supply.
-Disconnected or obstructed pressure tubing.
-Low inducer voltage

I don't think it's vent sizing or restriction. The vent is pretty well enclosed and it goes out and up at 90 degree with an end-cap on it.

Finally found the pressure switch tubing, it's only about 2-3 inches long, it's directly behind the pressure switch and goes straight back into what is the inducer housing I believe?

Not sure what or where the start compacitor is? That the battery like thing on the blower? Maybe I should check that next?

The inducer motor comes on immediately when I call for heat and continuously runs. I got a 124 volt reading on it which I believe is good. Maybe the wheel or other parts are dirty and stuck since I rarely replaced the air filter?

It's been very cold here, I don't know if it's possible something got frozen.. however I don't see any condensation anywhere. This furnace is actually located out in my detached garage.


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## yuri (Nov 29, 2008)

remove the pressure switch and very carefully pull the tubing off and clean the port on the fan with a drill bit. that tinypic service does not work well for me or show your pics. gets XXX sites. try photobucket or imageshack and put the actual link here.


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## Jesper (Feb 27, 2014)

Removed the pressure switch (Model# FS6410-626) and cleaned around small fan hole (port?) with drill bit

I've added an album on imageshack with all the photos.

https://imageshack.com/a/WLuq/1


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## yuri (Nov 29, 2008)

http://www.diychatroom.com/f17/york-furnace-pressure-switch-stuck-open-troubleshooting-195859/

You need to clean out that port hole. If the pressure switch is not closing then it may be faulty or the inducer fan is not creating enough draft to close it. Read that link and you may have to buy a manometer to check it properly and there is one in it that I use. Check the chimney for obstructions and remove the exhaust pipe to the chimney from the top of the furnace and look for dead birds in there. Or call a Pro as he has the manometer and experience to check the reasons that switch may not close and your wiring etc etc.

http://www.diychatroom.com/f17/need-help-troubleshooting-furnace-196828/

Read this link to.


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## Jesper (Feb 27, 2014)

Want to make sure I'm not damaging anything before I go sticking things in holes.









Above picture is the hole the pressure switch tubing went to.









Above picture is the hole behind the inducer fan/cage.

Popped the endcap off outside and looked down there with a flashlight, it all looked clear.


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## Jesper (Feb 27, 2014)

As far as manometers go, would I need the single or dual?

http://www.amazon.com/UEi-Test-Inst...UTF8&qid=1393615388&sr=8-3&keywords=manometer

http://www.amazon.com/UEi-EM201-Dif..._sim_hi_9?ie=UTF8&refRID=0VYM9VZH6WKMM8S4NW69

Also, there are some significantly cheaper models on amazon,
http://www.amazon.com/Fieldpiece-SD...UTF8&qid=1393615463&sr=1-2&keywords=manometer
or
http://www.amazon.com/Meters-PDMM01...UTF8&qid=1393615388&sr=8-1&keywords=manometer

Considering, I'm not doing this for a living are these good options? Obviously, there are some sacrifices between the different models. Most likely probably the material (i.e. light duty vs heavy duty)


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## yuri (Nov 29, 2008)

You ream out this hole in red. The fieldpiece for $113 looks good. The cheap one is a Chineez knockoff and I stay away from that stuff. Get a dual one as it may be useful someday if you get a high efficiency furnace. The UEI is smaller and more Pro friendly but Fieldpiece is very popular with Pros as well. The single will work but the dual is better in the long run.


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## Jesper (Feb 27, 2014)

Got the Fieldprice manometer today. Am I going to need to buy additional tubing/pieces? It came with a long tube with a threaded bolt on one end, an adapter tube and an adapter piece. The youtube videos I watched they were using plastic t-joint piece? That just for dual pressure switches?


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## beenthere (Oct 11, 2008)

You can get plastic tees from an automotive parts house.


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## yuri (Nov 29, 2008)

all you need to do is take the hose off the pressure switch and get a piece of hose that diameter from a auto parts store/vacuum hose and put it on your manometer and follow its instructions on how to use and zero it. then look at the pressure switch to see if it has a rating like .43"WC. Start the furnace with your manometer on that port the tube attaches to and you drilled out and the pressure switch disconnected and see what the vacuum is. it will run for 30 seconds before locking out and giving you the error code. no need to tee into that line plus it is so short that may be impossible. usually those switches are rated for .4 to .5"WC to close. if it is less than .4 you got a problem with the ventor fan or some obstruction.


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## Jesper (Feb 27, 2014)

0.62 inWC was the reading I got. The actual pressure switch does not say the WC rating.

Blue label says:
Model: FS6410-626
P/N: HK06WC073
Mount Diaphragm Vertical

On the back it has numbers.. 011718 1090


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## Jesper (Feb 27, 2014)

Took apart the exhaust piping for any blockage. I did find a small hornets nest, everything else was clear. Still getting the same problem.


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## yuri (Nov 29, 2008)

I worked on thousands of Carriers and those switches are usually.43"WC. You need a new pressure switch. Use that HK number when ordering it as that is what Carrier uses. Try pexsupply.com


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## Jesper (Feb 27, 2014)

I couldn't find the exact HK06WC073 being sold, except in used condition on eBay.. but I found out on another site that HK06WC090 is a replacement for the HK06WC073.

Ordered HK06WC090 through pexsupply.com



> The Part # is HK06WC090 (also replaces old part #s HK660001, HK06WC073, HK06WC074, HK06WC076, HK06WC086 & HK06WC088)! It works on many Carrier/Bryant/Payne gas furnaces!! Thanks for looking and good luck!
> 
> Many older switches are metalic, but they have all been updated/replaced with black plastic switches! They are direct replacements!


I should have it in a few days (Wednesday-Thursday)
Thanks


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## Jesper (Feb 27, 2014)

Fast shipping! Already got my part next day. Installed it. however there are some small problems. The top wire is too short to reach the bottom connector.. and on both ends of the wires, the connectors are too small.

It does matter which wire goes to which connector, right? The old one and new one had the same labels marked NO and C on the pressure switches. So that top orange wire needs to go to the bottom marked NO as it was on the original pressure switch. The yellow wire does have enough length to reach the top connection, but the end connector is too small to fit on the gold connection.

The orange wire is labeled:
AWM 105ºC Style 123f YW-1 600V Moisture Resistant 60ºC LL-39697 CS

Should I just take this wire to a local Lowes or Auto Zone? Would they have what I need?


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## beenthere (Oct 11, 2008)

Makes no difference which wire is on which connector. its just a switch.

Just have to get a 1/4" connector and crimp it on the wire instead of that 1/8".


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## Jesper (Feb 27, 2014)

Thanks, got it installed. But it's still not working, must be some kind of blockage at the inducer?


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## hvac27 (Feb 27, 2014)

You either have a blockage somewhere or your board is bad. Pressure switches rarely fail. Have you replaced your control board?


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## Jesper (Feb 27, 2014)

Yes, I replaced the control board.

1. First I replace the ignitor (though I don't think the old one was bad, good to have an extra anyway I guess)
2. Then I replaced the limit switch (figured since I didn't replace my air filter at all, it would be bad and was very dirty when I removed it)
3. Then I replaced the control board (not sure if the old one was bad.. just the old one didn't have a LED light to give me an error code)
4. I also pulled out the blower wheel and took it to the carwash to clean it.
New control board LED light gave me error code 31.
From what I could see, from when I pulled out the limit switch and blower. The heat exchanger is in good condition, no rust or cracks.
5. Checked the exhaust piping and it was clear of all obstructions.
6. Now I replaced the pressure switch.

There is a noise coming form the inducer, so that's why I think it may be something with it and it was quite dirty from what I could tell.

There is also a small switch above the pressure switch (as shown in the above post) but the red button is out.

With the tstat off, and switching the fan to ON, on the tstat, the blower comes on and operates as normal.

I'm sure I wired it all correct, same as it was on the old board.. How would I go about checking the control board? There is nothing that seems to be burned or damaged.


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## hvac27 (Feb 27, 2014)

You don't! You check everything around the board. If all your other electrical components are checking out to carrier specs/name plate your board is bad. Make sure all your resettable switches are pushed in. If you can send a pic of the entire furnace, close up of the control board and the wiring diagram. I want to make sure of everything.


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## beenthere (Oct 11, 2008)

Post a pic of the switch with the red button sticking out. That may be a spill switch, which would indicate a problem with either the inducer or the flue pipe/chimney itself.


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## hvac27 (Feb 27, 2014)

Also did you remember to reconnect the hose to the pressure switch?


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## hvac27 (Feb 27, 2014)

If you have an iPhone ill FaceTime you so we can get you some heat....


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## Jesper (Feb 27, 2014)

It's working!! Heat!! I pushed in the button above the pressure switch, I'll still post a pic of it in a minute, it was tripped. So I want to know why that switch is there and what would trip it. It does have a direct wire from it to the pressure switch and then a wire from it down to the control board. Yes, the pressure switch has the tube behind it to the port.

I think maybe I did something at the thermostat to cause it to trip? Say I set it to 60 degrees. So it heated the room from 60 degrees up to 65 degrees and kicked off like it should. But then say I went over to the tstat and set it to 70 degrees almost immediately after it kicked off. Would something like that cause it to trip/fail?


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## hvac27 (Feb 27, 2014)

It's a temp limit for your flue pipe. Prob had some back draft do to excessive wind, causing that limit to get hot. Good stuff bro! I admire your determination!


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## yuri (Nov 29, 2008)

If you have a negative pressure in your house causing wind to come down the chimney it will trip that fumes spill switch. Usually cause by a wood burning fireplace or powerful kitchen exhaust fan sucking too much air out of the house.


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## beenthere (Oct 11, 2008)

Check your flue/chimney to make sure it is not obstructed.


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## Danbob (Nov 3, 2015)

My furnace went out last night and I thought it might be the igniter since it has failed in the past. I had a spare on hand and so I swapped it out but no luck. The inducer just ran continuously and no glow or blower to be had.... 

Anyway to make a long story short I found this thread after a few hours searching and it basically saved me hours and likely many $$'s too. It turned out to be the same limit switch (the flue/draft temp limit switch). I cleaned it and reset it and everything seems to be working fine now. I checked all the suggested probable causes for intake or exhaust restrictions and everything seems good. I am going to chalk it up to having run my kitchen fan and bathroom fan at the same time (about 450 cfm total) for quite some time while making a roast chicken yesterday -it was smoking like crazy...

I would however like to eliminate the switch from the equation by replacing it with a new one. In case it trips again in the near future I can know it's not because of an old faulty sensor/switch. Does anyone know how to identify the part? There is only a US Patent number on it. 4349806 Klixon brand. The top of the switch is marked in yellow. My furnace is a Carrier Crusader model: 58SSC075-GC | series 110 and the product number is 58SSC075-C-111GC. I can't seem to find the exact product number online. Is a model number match close enough? Or should I not bother replacing it??

Thanks


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## yuri (Nov 29, 2008)

I have never had one fail so I would leave it alone. If you want to then you need to get it from Carrier.

americanhvacparts.com or supplyhouse.com may be able to look it up.


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## Danbob (Nov 3, 2015)

Thanks for the quick reply and advice Yuri. It's good to hear that you have never experienced one failing. I had nothing to gauge with (ie. whether they fail all the time, some of the time, etc.) I think I will take your advice and leave it be. Time will tell and I will avoid all my house exhaust fans running at the same time when it's cold outside!


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## yuri (Nov 29, 2008)

You also should have new CO detectors in your house. If you have a water heater on that chimney it could be dangerous as they have no protection from downdrafts.


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## Danbob (Nov 3, 2015)

Coincidentally I was just thinking about picking up a couple more CO detectors. I only have one right now. (small home - 1K sq.ft.) And I do have a hot water tank on the chimney too. It is an older home with a 'sleeved' brick chimney. Been here 16 years with the same furnace since we got here but put in a new hot water tank and chimney sleeve in the past 5.

I will definitely buy some new CO detectors now. Thank you for all your advice. I really appreciate it.


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## user_12345a (Nov 23, 2014)

co alarms offer only minimal protection from life threatening co, not low level long term exposure.


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## Danbob (Nov 3, 2015)

good point user_12345a.


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## Danbob (Nov 3, 2015)

what about a detector like this:
http://www.kidde.com/home-safety/en/us/products/fire-safety/co-alarms/kn-cou-b/


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## yuri (Nov 29, 2008)

All CO detectors provide good safety against high exposures to CO like a blocked chimney unless they are over 10 yrs old. If you want better protection to very low levels over a long period of time you have to spend over $75 to get more sensitive units. Senco makes some expensive units and this Kidde one suggested list price is close to $200. Probably sells for $100 so at that price point is a very accurate well calibrated unit. Parent company is United Technologies which along with Honeywell and SIEMENS is one of the biggest companies in the world. Owns Carrier and a bunch of other companies so it should be a good unit.


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