Furnace not turning on reliably!


  #1  
Old 12-12-13, 06:34 AM
J
Member
Thread Starter
Join Date: Dec 2013
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Exclamation Furnace not turning on reliably!

Hi! We have a gas furnace from 1997. The issue is that sometimes it will turn on and heat the home (to 70 degrees where we have the thermostat set) and then sometimes we'll wake up in the morning and it will be 54 in the house. I've checked the vents, exhaust outside the house, filters everything seems to be fine. Thermocoupler works and flame fires up.

I think I might know the issue, but wanted to see if this sounds right or if there could be something else to blame?

So when the furnace hasn't kicked on and it's really cold in the house, the solution that fixes it is going to the thermostat, switching it to "off", waiting for 5 seconds and then switching it back "on". After that you can hear the "tick" of it sending the signal to the furnace and the heat kicks on.

This leads me to believe that the culprit is the thermostat? Just wondering why it's so "touch and go" and also if there may be something else to blame? If it could be something else, why would it be solved by turning the thermostat off then on again?

Any input is MUCH appreciated! If it's the thermostat then great, we'll replace it. But I'd probably be looking to replace it with a Nest, and want to narrow down the option and make sure that is most likely the issue before dropping $250 on a new thermostat.

Thank you!
 
  #2  
Old 12-12-13, 11:07 AM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 64,939
Received 3,952 Upvotes on 3,545 Posts
Welcome to the forums.

Your furnace should have a diagnostic LED on a control board. The board may be down below in the blower cage. If it's there.... there will be a round sightglass in the door that you can look in and see it blink a trouble code. The codes will be listed on the inside of the blower door.

Opening the blower door or turning off AC power will erase the trouble codes.

You can also try bypassing the thermostat wiring by temporarily shorting from the R terminal at the furnace to the W terminal.
 
  #3  
Old 12-12-13, 11:55 AM
J
Member
Thread Starter
Join Date: Dec 2013
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thanks for the response!

So if the thermostat is not working correctly there will be an error code on the furnace?

I have no clue nor do I want to risk messing anything up by attempting to "bypass" anything... thanks for the tip though!
 
  #4  
Old 12-12-13, 12:18 PM
T
Member
Join Date: Jul 2008
Location: Kansas
Posts: 264
Upvotes: 0
Received 0 Upvotes on 0 Posts
The bypass that PJ is suggesting is necessary in order to rule out buying an expensive Nest stat and still having a problem. Sometimes it's the stat. Most times it's in the system itself. Jumpering out the stat will give you and us more clues.
 
  #5  
Old 12-12-13, 12:37 PM
G
Member
Join Date: Oct 2002
Location: Hamilton County, Ohio
Posts: 3,927
Upvotes: 0
Received 2 Upvotes on 2 Posts
There is a lot more going on at the furnace than a tick and the heat comes on.

You really need to observe the furnace and look and listen as it goes through various stages while preparing to deliver heat. An intermittent problem can best be found by watching the furnace.
 
  #6  
Old 12-12-13, 03:06 PM
A
Member
Join Date: Dec 2013
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
I am having the EXACT problem as the OP. 2x in the past week I've woken up to a house in the low to mid 50s, rather than 70, like it should be. Last time, all I had to do was leave it be and it fixed itself - by the time I came home from work that day, it was working fine, producing heat again. Today, however, it actually got cooler, and it is still blowing cold air through the vents. Today I already tried turning off the power at the breaker, turning off the gas supply to the heater and waiting the 5 minutes in the directions, and still nothing. We're having the coldest temperatures in 3 years right now, and I don't want to subject my 12 week old puppy (or myself) to the even lower possible temps overnight tonight, so ANY fixes would be helpful.

I saw the trick of bypassing the thermostat - can you walk me through that? Now that I look back at the error codes for the LED, I think it is telling me the status is "normal no call for heat," which makes me wonder...(and I installed the thermostat myself a couple of months ago, so it doesn't really surprise me that it could be the culprit.)
 
  #7  
Old 12-12-13, 04:17 PM
T
Member
Join Date: Jul 2008
Location: Kansas
Posts: 264
Upvotes: 0
Received 0 Upvotes on 0 Posts
If you installed the stat yourself, short the red and white wires together at the stat and see if that works. If it does, it's a stat problem. If it doesn't ,trace the stat wires at the furnace and do the same at red and white to see if that does.
 
  #8  
Old 12-12-13, 04:29 PM
A
Member
Join Date: Dec 2013
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
Short them together as in make them touch? In which place, the R or the W?
 
  #9  
Old 12-12-13, 05:28 PM
T
Member
Join Date: Jul 2008
Location: Kansas
Posts: 264
Upvotes: 0
Received 0 Upvotes on 0 Posts
If you changed your stat, take the cover off, twist the red and white together or short with a paper clip between R &W, being careful not to touch other wires and see if it runs. Take apart to see if it shuts of properly.
 
  #10  
Old 12-13-13, 06:07 PM
A
Member
Join Date: Dec 2013
Posts: 3
Upvotes: 0
Received 0 Upvotes on 0 Posts
I tried, and nothing (literally, nothing) happened. My uncle specializes in HVAC/electrical, so I think I'm stuck for one more night without a heater, but he's going to try to come out tomorrow to fix it - assuming we don't get the 5-8" of snow they're forecasting for us. I've got 2 decent sized space heaters going, so the thermostat says it is up to 57 now...heat wave at my house!
 
  #11  
Old 12-14-13, 08:42 AM
S
Member
Join Date: Sep 2008
Location: Long Island
Posts: 695
Upvotes: 0
Received 0 Upvotes on 0 Posts
fist is to remove the stat off the subbase and jump as said R to W no switching required...nothing....remove jump there and jump R to W at the furnace unit lights off and heats you have a wire problem not a stat problem...if you have any AM/PM settings the clock has to read the correct "Time Of Day" to swing the modes from one temp to another with that AM/PM timed setting and temp.but doing those jumps gets you off the furnace within problems
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: