Strange Furnace Problem
Hi, I have a strange problem with my furnace that no one can figure out. I know the rules of this forum state NO DIY but I dont know were else to turn. I already paided a service tech to come out to my house to check the furnace and he couldnt find the problem. There was nothing he could do for me. Could someone please help me!
This is a Bryant gas-fired, induced combustion furnace. Its about 20 yrs old.
This is the problem I am having.
1. Furnace works properly when its 50 degrees or higher outside. The furnace only has to stay on for short periods of time to keep the house temp. at the thermostat setting.
2. As the temperature outside drops the furnace has to stay on for longer periods of time to keep the desired temperature.
3. Sometimes the furnace will shut down before temperature on thermostat is reached. It shuts down in this order:
a. inducer motor shuts off
b. furnace flame goes out
c. main blower shuts off after a couple of minutes
4. Furnace attemps to restart in this order:
a. inducer motor starts
b. Im assuming pressure valve closes because I have tested it and it seems to work properly.
c. pilot sometimes lights and sometimes doesnt.
d. inducer motor stops.
e. inducer motor starts after a few seconds and the whole process is repeated.
f. eventually the furnace will light. Sometimes it takes up to 15 of these cycles for the furnace to light.
g. after the furnace lights, sometimes it will stay on for only 15 seconds and other times for 15
minutes other times in between.
5. If I shut the furnace off for a 15 minutes or so and restart it, it will start and run fine.
6. My schematic shows 1 Limit Switch and 1 Auxilliary Limit Switch, both are manual reset.
7. Ive replaced the Standing Pilot, the Inducer Motor circuit board and the Blower Motor board.
Something seems to be shutting off the inducer motor. The colder it gets outside and the longer the furnace has to stay on, the more the furnace cycles without lighting.
Ive Bypassed the limit switches, Ive bypassed the thermostat, disconnected the pressure switch, took the hose off the the pressure valve, and disconnected the pilot assembly. I did these 1 at a time and all at once and the inducer motor still cycles even with everything disconnected.
My gas valve pressure is a little high but I cant adjust it because the whoever installed this furnace stripped the adjusting screw.
Has anyone run into a problem like this before? Can anyone give me an idea on what to try next? Any help would be appreciated. Thank you.
Thanks for taking time to read the rules most people do not.
It would be difficult to properly diagnose your problem over the internet. You will need to call your service company back. Or if the tech can't figure it out ask for a senior tech to come out, or call a different service company. A 20yr old furnace has probably exceeded its expect life. I would want to make sure that it is safe to use, let alone worth repairing. I do not reccomend jumping out limits or any other safety device. There are ways of testing these items.
I never let schooling interfere with my education... Mark Twain
In the DC area, we have "The Washington Consumer's Checkbook", which keeps tabs on all kinds of companies and repair shops. They give (or not) a check mark for price and a check mark for quality.
Maybe there is a similar pub. in your area that can steer you to a reputable company.
probably time to have it replaced
This is not a DIY help site. Please call a service company to resolve your heating issues.