American standard 3-flash error

Old 12-18-15, 02:30 AM
Thread Starter
Join Date: Dec 2015
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
American standard 3-flash error

Good Evening fellow do it yourselfers.

Since I always read the great forums here to help me with my projects, I figured why not start posting on my own and getting more accurate assistance.

I have a 90% gas furnace American Standard at home, that has been giving me problems this winter. These are my first issues with the machine as it is rather new. Luckily for some freakish reason it's 60 degrees here in New England.

I am getting the 3 flash error message, pressure sensor error, and have attempted the following.

Check ventilation, I checked thoroughly on the roof for any obstructions as well as disconnecting the vent inside and feeling a strong flow, obstruction free.

I tried jumping the pressure switch, before and after it was running.

Something that seems odd is that the error code starts flashing after only about 5 seconds of operation, is this normal?

Any information to try would be really helpful and appreciated!

Old 12-18-15, 05:32 AM
Group Moderator
Join Date: Mar 2003
Location: NC, USA
Posts: 27,517
Received 2,114 Upvotes on 1,893 Posts
You said you jumped the pressure switch but didn't say what the result was. Do you happen to know if that switch is normally open or closed?

Did you check the hose(s) leading to the pressure switch? It must be completely clear as water or a spider nest can stop it from working reliably. Another test is to hook your meter up to the switch and gently blow or suck on the tube to see if the switch is electrically opening and closing.
Old 12-18-15, 09:24 AM
Thread Starter
Join Date: Dec 2015
Posts: 2
Upvotes: 0
Received 0 Upvotes on 0 Posts
There where no changes to the start-up cycle while jumping before and after. Same error code. I did check vent hose, it also sounds like the diaphragm is clicking. I blew into hose going into pressure sensor. Then blew in hose going into inducer, no obstructions.

I tried using a multimeter and testing the P.S. But it seemed as if I needed 4 hands to do that job, and I've no help.

I ordered a new switch a couple of days ago, so it should be here today. I'm just worried after reading everywhere that it's probably not the problem.
Old 12-18-15, 02:11 PM
SeattlePioneer's Avatar
Banned. Rule And/Or Policy Violation
Join Date: Jul 2007
Location: Seattle, Wa
Posts: 4,469
Upvotes: 0
Received 1 Upvote on 1 Post

Sucking on a pressure switch is NOT a good idea. The diaphragm of the pressure switch is easily damaged or stretched out of proper calibration.

Test to see if the pressure switch is open when the thermostat first calls for heat and then if it closes when the inducer motor comes up to speed.

When a pressure switch fails to close, it's quite rare for the pressure switch to be bad, so changing it out is usually a waste of time and money.

The problem is almost always some defect in the air supply to the furnace, the venting system from the furnace, something plugging up the combustion air flow through the furnace, something plugging up the condensate drainage system (in condensing furnaces), defective inducer motor or inducer fan wheel defect or something impairing the pressure being applied to the pressure switch (hose or inducer motor hose fitting)

ANY of those things are a lot more likely to be the cause of the problem than a bad pressure switch.

A pressure switch diagnostic code is one of the common reasons a gas furnace wont turn on. Unfortunately, because of the wide variety of things that can cause that condition, it is often tough for DIYers to isolate the particular cause of the problem.

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