Comfortmaker Furnace won't start, but A/C does. Please Help!

proenproOctober 29, 2011

Hello,

I have two newer (~ two y/o) Comfortmaker furnaces, one for my first floor and the other for my second. The one for the first is working fine, but second floor heat does not go on. I began troubleshooting the faulty second floor furnace by replacing the thermostat, hoping that that would resolve the problem, but that did not work. The non-functioning system's diagnostic code (three long flashes) on the control board indicates "pressure switch is open when should be closed." While on the good system I've got the "heartbeat, or normal operation" - steady quick flashing.

When I power off/on breaker for the bad system the control board has a heartbeat for about a minute, then switches to the three long flashes (when thermostat set to heat). I tested the A/C on the faulty system and it works fine, with control board maintaining a steady, consistent heartbeat.

Additionally, I've powered off both systems at breaker, disconnected wiring from the pressure switches, checked them out with multimeter and both read the same (1), which leads me to believe that the pressure switch on faulty system is good.

I'm confused. Any advice or assistance would be greatly appreciated.

Many thanks in advance,

proenpro

Thank you for reporting this comment. Undo
icemate

How old is your furnace ? If it has a draft inducer blower motor, it must be working properly and up to speed. This closes the pressure switch and starts the ignition of the furnace. To make sure there is no problem with the exhaust or inlet, check them out. Very likely change the draft blower and it will work.

    Bookmark   December 9, 2011 at 1:10AM
Thank you for reporting this comment. Undo
heatseeker

icemate is off base, sounds like a clogged hose.

    Bookmark   December 13, 2011 at 1:22PM
Sign Up to comment
More Discussions
HVAC billing question
Question for the pros...... So I had a faulty capacitor...
spe720
No Fully Trained Mini Split Installers
Reading threads about mini split heat pumps I got curious...
nerdyshopper
Does Air Duct Cleaning really help?
We live in a 40 year old home with a forced air gas...
lincann
Need help with selecting Eff Heat Pump replacement.
20 yr old American Std Heat Pump stopped working. ...
2015hvac
Is this HVAC system OK?
Replacing original old ~9 seer unit. House is 2001...
thereloader
Sponsored Products
Eero Saarinen Dining Table
| Italy Design
Fresca Walnut Modern Double Sink Bathroom Vanity w/ Medicine Cabinet
Hudson Reed
Loop: Groovy Mats Flooring Light Brown 24 in. x 24 in. Comfortable Carpet Mat
$3.99 | Home Depot
Triple Concealed Thermostatic Shower Valve, Square Head & 4 Body Jets
Hudson Reed
Henri Studio Europa Murabella Lavabo Garden Fountain
Lamps Plus
Elk Lighting Monastery Trinket Box - 51-0248
$60.00 | Hayneedle
Two Loma Side Chairs
$599.00 | Horchow
Elk Lighting 19.5H in. Ruby Vase - 93-5860
$114.00 | Hayneedle
People viewed this after searching for:
© 2015 Houzz Inc. Houzz® The new way to design your home™