Hi all,
I have an American Standard Freedom 80. As nights are getting colder I have found that the furnace does not heat although it performs most of what it suppose to do as follows:
1. power on (blinks slowly as expected)
2. thermostat calls for heat (blinks fast as expected)
3. vent starts
4. ignition starts
5. burners fire up
6. blower starts BUT stops after about a minute. Code: 3 flashes.
Any suggestions?
Thank you so much!

 

What's the model #? Should be located inside the burner section.

 

Welcome to the forums.

Definitely need the full model number on this unit.
A code 3 is a pressure switch issue. That usually occurs at startup..... not after burner is lit.
You may have two pressure switches on that furnace.

 

Thank you for your replies.
Apparently it is a Freedom 90 (not 80, my apologies).
Model # AUX080C960D2
A couple of photos from burner side are attached.

 

You need to keep in mind that as the efficiency gets pushed higher on these furnaces maintenance goes up. It is important to get a furnace like this checked and cleaned at least every other year.... although every year is better.

A- pressure switch, B- gas valve, C- draft inducer, D- condensate drain, E- ?????

The pressure switch is what's signalling your system there is a problem. One problem is the condensate drain line needs to be removed and cleaned. The pressure switch is usually connected to the draft inducer but yours seems to be connected to the upper plenum and gas valve thru a small black hose. I need to know if E is a hose and where it goes.

 

E is a hose coming from the back of the pressure switch and goes to the back panel. Immediately below there is thicker short hose that goes from the back panel to the condensate trap. (see photo). What is behind the back panel that they did not connect the hose directly to the trap? If that part is clogged I should clean it. Since this is where air flows it makes some sense that the issue starts shortly after air forced by blower.
Thank you!

 

I'm not totally familiar with the drain lines on this unit and I can't find the service info I need.
I do know that a partially clogged drain line can cause your problem.

Make sure the clear hoses are clean.

 

Thank you!
I looked at the hoses. They look clear. Should the condensate trap (box) contain water? Is is empty right now.
I have tried again and it all works well ...UNTIL. As soon as the blower starts the fire dies and code 3 flashes appears.