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Help with furnace limit switch issue

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  • Nov 21st, 2019 5:12 am
Jr. Member
Jun 20, 2012
160 posts
23 upvotes
Toronto, Ontario

Help with furnace limit switch issue

Hello Everyone, need some input here diagnosing an issue with my single-stage York furnace.

Symptom - furnace runs and raise the temperature by a few degrees (produce heat for maybe 45 mins), and then for a brief moment the blower stops and restarts but only cool air comes out of the registers. The blower would continue to run for maybe 30 mins until it produces heat again. During the time in which cool air blows out, the panel displays 4 red flashes error code.

The filter was changed just a couple of weeks ago and still in good shape. After looking online it appears to point to one of the three limit switches (main limit switch, inducer limit switch, the flame rollout switch) might be the issue. Anyone have experience with this? Does it sound like the switch is doing what it's supposed to or seems faulty? Any input or help is appreciated!
8 replies
Deal Guru
User avatar
Mar 13, 2004
13840 posts
5545 upvotes
Ontario
Sounds very similar to one of the many issues we had with our old York furnace that I just replaced a few weeks ago as you can read here - new-furnace-time-2322131/

So I had the same issue due to the furnace running to long & getting to hot so it would trip the limit switch (however mine would just blow cold air until we cut power to it. Basically for us our furnace was oversized for our home, we had a 80,000btu furnace and currently went down to a 40,000btu 2-stage.

To resolve your issue you can try a few things that may Help but may not resolve it as your furnace could be too big (How big is it?)

- Open ALL registers do not close any as that will restrict airflow and cause it to get hotter.
- Consider opening another air return to help the furnace breath
- Sometimes you can change the blower speed to higher to help push out the hot air so it wont trip the limit switch.
- Clean the A coil in the furnace which could be dirty and restricting air flow.
btcoma wrote: Hello Everyone, need some input here diagnosing an issue with my single-stage York furnace.

Symptom - furnace runs and raise the temperature by a few degrees (produce heat for maybe 45 mins), and then for a brief moment the blower stops and restarts but only cool air comes out of the registers. The blower would continue to run for maybe 30 mins until it produces heat again. During the time in which cool air blows out, the panel displays 4 red flashes error code.

The filter was changed just a couple of weeks ago and still in good shape. After looking online it appears to point to one of the three limit switches (main limit switch, inducer limit switch, the flame rollout switch) might be the issue. Anyone have experience with this? Does it sound like the switch is doing what it's supposed to or seems faulty? Any input or help is appreciated!
Member
Dec 22, 2016
387 posts
354 upvotes
SW Ontario
I had the same issue this year on my Payne. I ended up replacing it. My buddy came to take a look and tried pretty much all the above suggestions. I would always get the limit switch eventually. He suggested I get it replaced due to year and efficiency plus cost of maybe finding a solution. I even got my ducts cleaned. Lol. I also needed a new AC so it was done all at once. Sucks but no matter what I did it never lasted long and progressively got worse.....and I have kids so I couldn't risk no heat.
Deal Addict
Jun 16, 2009
4517 posts
3449 upvotes
Vaughan
MAIN reasons of furnace to short cycle :
1. Oversize furnace
2. Clogged filter of clogged A coil.
3. Undersized ducts
4. Furnace overfiring
5. Limit switch is defective ( rarely)
6. Defective heat exchnager
7. A coil mounted right above the furnace
Though above list is not exhaustive, these are top reasons. If you provide make and model of your furnace alongwith rough age, we can shed more light.
btcoma wrote: Hello Everyone, need some input here diagnosing an issue with my single-stage York furnace.

Symptom - furnace runs and raise the temperature by a few degrees (produce heat for maybe 45 mins), and then for a brief moment the blower stops and restarts but only cool air comes out of the registers. The blower would continue to run for maybe 30 mins until it produces heat again. During the time in which cool air blows out, the panel displays 4 red flashes error code.

The filter was changed just a couple of weeks ago and still in good shape. After looking online it appears to point to one of the three limit switches (main limit switch, inducer limit switch, the flame rollout switch) might be the issue. Anyone have experience with this? Does it sound like the switch is doing what it's supposed to or seems faulty? Any input or help is appreciated!
Certified HVAC Pro. Committed to Customer, not brand. Past RFD Review
2024 AC, Furnace, Heat Pump and Water Heater Groupbuy
Jr. Member
Jun 20, 2012
160 posts
23 upvotes
Toronto, Ontario
Thanks, I'll read through your thread.

Oh that was something that I did recently, closed a few of the unused bedroom and washroom registers. I'll try that first and see if it runs smoothly.
sickcars wrote: Sounds very similar to one of the many issues we had with our old York furnace that I just replaced a few weeks ago as you can read here - new-furnace-time-2322131/

So I had the same issue due to the furnace running to long & getting to hot so it would trip the limit switch (however mine would just blow cold air until we cut power to it. Basically for us our furnace was oversized for our home, we had a 80,000btu furnace and currently went down to a 40,000btu 2-stage.

To resolve your issue you can try a few things that may Help but may not resolve it as your furnace could be too big (How big is it?)

- Open ALL registers do not close any as that will restrict airflow and cause it to get hotter.
- Consider opening another air return to help the furnace breath
- Sometimes you can change the blower speed to higher to help push out the hot air so it wont trip the limit switch.
- Clean the A coil in the furnace which could be dirty and restricting air flow.
Jr. Member
Jun 20, 2012
160 posts
23 upvotes
Toronto, Ontario
How old was your furnace when you replaced it? Mine is builder grade Neutral Face from '07 lol
CanadianMatt wrote: I had the same issue this year on my Payne. I ended up replacing it. My buddy came to take a look and tried pretty much all the above suggestions. I would always get the limit switch eventually. He suggested I get it replaced due to year and efficiency plus cost of maybe finding a solution. I even got my ducts cleaned. Lol. I also needed a new AC so it was done all at once. Sucks but no matter what I did it never lasted long and progressively got worse.....and I have kids so I couldn't risk no heat.
Last edited by btcoma on Nov 20th, 2019 1:03 pm, edited 1 time in total.
Jr. Member
Jun 20, 2012
160 posts
23 upvotes
Toronto, Ontario
Interesting, I think 2 and 5 might be the culprit(s). For limit switch, I guess checking for continuity might rule it out. I'm going to check where the A coil is located and see.

It's a GM9s080b12up11j York/Coleman (12 years old)

Thanks!
newlyborn wrote: MAIN reasons of furnace to short cycle :
1. Oversize furnace
2. Clogged filter of clogged A coil.
3. Undersized ducts
4. Furnace overfiring
5. Limit switch is defective ( rarely)
6. Defective heat exchnager
7. A coil mounted right above the furnace
Though above list is not exhaustive, these are top reasons. If you provide make and model of your furnace alongwith rough age, we can shed more light.
Deal Addict
User avatar
Aug 12, 2007
4685 posts
830 upvotes
Waterloo
newlyborn wrote: MAIN reasons of furnace to short cycle :
1. Oversize furnace
2. Clogged filter of clogged A coil.
3. Undersized ducts
4. Furnace overfiring
5. Limit switch is defective ( rarely)
6. Defective heat exchnager
7. A coil mounted right above the furnace
Though above list is not exhaustive, these are top reasons. If you provide make and model of your furnace alongwith rough age, we can shed more light.
If the intake air is thru a vent pipe. blockage in the pipe can also cause it to trip. Or the vent exhaust being blocked also causes the same issue.

Considering furnace does run for 45 minutes without tripping , To me it means there is a malfunction somewhere rather than a sizing issue.
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Deal Addict
User avatar
Mar 4, 2007
2379 posts
504 upvotes
Vancouver
Hi,

Sounds like the limit switch has gone south. The limit switch in my ancient furnace caused the blower motor to run continuously, regardless of the thermostat setting. If the limit switch is a separate controller, would be worth your while to check it out before replacing the whole furnace.
https://www.amresupply.com/catalog/Fan- ... trols-HZ3D

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