# Furnace help...won't heat past 67



## goodtimes (Dec 5, 2011)

I need some help and hopefully someone out here can give me some advice. I have an older forced air gas furnace (armstrong) that will not heat the house past 67 degrees. 

I have just replace a burned out 1/3hp blower motor a week ago and replace the belt and fan limit switch at the same time. The limit switch seems to work fine as the flame kicks on when I call for heat at the thermostat and will kick off if I can get to 66 degrees (then turn the thermostat down). The limit switch is set correctly for the 3 set points.

The problem is that no matter how high I set the thermostat I can't get the temp in the house up past 67. The flame kicks on intermittently and the blower goes almost constantly...still won't warm up past 67. Any ideas or thoughts? I would appreciate any ideas you all may have.

Thanks,

John


----------



## Marty S. (Oct 31, 2009)

Sounds like the limit is tripping. When's the last time you had the antique (belt drive) inspected and serviced.


----------



## ben's plumbing (Oct 6, 2011)

goodtimes said:


> I need some help and hopefully someone out here can give me some advice. I have an older forced air gas furnace (armstrong) that will not heat the house past 67 degrees.
> 
> I have just replace a burned out 1/3hp blower motor a week ago and replace the belt and fan limit switch at the same time. The limit switch seems to work fine as the flame kicks on when I call for heat at the thermostat and will kick off if I can get to 66 degrees (then turn the thermostat down). The limit switch is set correctly for the 3 set points.
> 
> ...


 is the motor going in the right direction...see this alot with homeowners...


----------



## dougp23 (Sep 20, 2011)

Also, don't minimize the effect leaky/drafty doors and windows can have on your furnace. I have seen this myself where we could not get the house to 68 without the boiler running for ages. Walked aRound and felt like someone had a window open, lol, it was drafty doors and windows. Plugged them up and heated much better. Probably not your issue, but worth investigating anyway.


----------



## biggles (Jan 1, 2008)

fan in lo/lo med was the squirrel cage installed as removed sounds like your going off on hi temp limit and not moving air


----------



## beenthere (Oct 11, 2008)

What temps do you have the 3 pointers set at?


----------



## goodtimes (Dec 5, 2011)

beenthere said:


> What temps do you have the 3 pointers set at?



Pointers are set at 100 / 150 / 200.

Motor is running the correct direction. Fan kicks in at the right temp, but the high limit kicks in not too long after the fan comes on.
I took a short video to show what is going on. 

http://www.youtube.com/watch?v=FGnngXj2ruI


----------



## beenthere (Oct 11, 2008)

When you point which direction the fan is running, you have your finger at the bottom of the motor/belt. From the looks of it, that would be the wrong direction. Reverse the rotation, and see if that does work better.

If you have an A/c coil on the furnace, it could be dirty, and need cleaned.


----------



## biggles (Jan 1, 2008)

that fan limit is mounted on the side of the unit :huh: and not up above the burner section it is definitly picking up the burner and doing what it should how's that fan panel coming off with the fan on should suck the panel...the fan in just fan how are the registers...and do you have ac there how about the evap coil


----------



## jkv (Oct 23, 2011)

Blower may not be moving enough air, dirty evaporator, filter, blower does appear to be backwards and move the control it is acting as if a stat is on a outside wall when the blower comes on it will pull air into the back side of the stat and cause the heat anticipator in the stat to go crazy.


----------



## goodtimes (Dec 5, 2011)

beenthere said:


> When you point which direction the fan is running, you have your finger at the bottom of the motor/belt. From the looks of it, that would be the wrong direction. Reverse the rotation, and see if that does work better.
> 
> If you have an A/c coil on the furnace, it could be dirty, and need cleaned.



The fan is blowing air out and into the burner box/past the flame...is that incorrect? There is air coming out of the register although not as strong as I would expect. I will check the ac coil and see if there is a blockage. Thanks for the suggestion. I will see if it helps tonight.


----------



## biggles (Jan 1, 2008)

there should no air coming out of the furnace in or around the burner section that blower assembly slides onto a rail then screw it down into the panel that seperates the blower secion from the furnace section..whats the word on that HI-limit location that should be in the heat exchanger section above the controls and burner...too close too hot...and what about removing the panel while the fan is on...is it sucking air...


----------



## goodtimes (Dec 5, 2011)

biggles said:


> there should no air coming out of the furnace in or around the burner section that blower assembly slides onto a rail then screw it down into the panel that seperates the blower secion from the furnace section..whats the word on that HI-limit location that should be in the heat exchanger section above the controls and burner...too close too hot...and what about removing the panel while the fan is on...is it sucking air...


The fan isn't sucking as much air as I would expect when I take the service panel off. Maybe it is clogged up on the other end?


----------



## beenthere (Oct 11, 2008)

Even running backwards, it will still blow air out the registers. Reverse it, and see if ti blows more air out. you have nothing to lose but a little time.


----------



## ben's plumbing (Oct 6, 2011)

goodtimes said:


> The fan isn't sucking as much air as I would expect when I take the service panel off. Maybe it is clogged up on the other end?


please check rotation again and biggles make good point.. fan and limit should be above furnace not that close to burnners


----------



## goodtimes (Dec 5, 2011)

ben's plumbing said:


> please check rotation again and biggles make good point.. fan and limit should be above furnace not that close to burnners



This is me eating crow. I reversed the motor and bingo. Thanks for the help everybody.


----------



## ben's plumbing (Oct 6, 2011)

thats great as i said we all make mistakes even the best..just keeps us humble..you did a very good job....ben


----------



## beenthere (Oct 11, 2008)

goodtimes said:


> This is me eating crow. I reversed the motor and bingo. Thanks for the help everybody.


Many years ago. I was rushing on a motor change out. Fired up the new motor and felt air blowing out of the register on the supply plenum. called it good and left. 2 hours later, the customer calls and says the burner keeps cycling on and off. Went back, and found it running the wrong direction. Ooops. It happens. 


Just glad it was something simple.


----------

