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dfferg 08-30-2005 08:20 PM

3 - flash code, american standard freedom 90 furnace
:confused: Its late August, thought I'd check out the american standard freedom 90 furnace. It worked fine last spring, but now flashing 3, for a "pressure switch error". 1) furnace does not even start up, but it has power. 2) hoses from two pressure switches, as wel as the rest are clear, no water present. Question, what pulls (or pushes) air flow to engage pressure switches? That seems to be the initial problem. Turn thermostat up, flashes normal - call for heat. Then it goes directly to 3 flashes. What to do? Thanks!

murray 09-12-2005 10:40 PM

I think the pressure switch is an air proving type ,the switch senses that the power vent fan is running ,if it does not sense a negative pressure it will go to error .check the other end of the tube where it hooks up to the draft assist fan clean it up ,turn the power off for a few minutes then turn it on .the draft assist fan should come on for 30 sec or so ,if its good the burners will fire ,then a minute or so later the blower will kick in .If not ,it would go to error,the draft assist fan will run for a few minutes then shut down and will not reset without turning the power off and on again .I bet a bug crawled in it :) If i,m wrong please someone post it ,I would like to know if my old wisdom is any good still:confused:

Tony 10-16-2005 04:14 PM

I was having this same problem, and upon looking it up I found your post. You were EXACTLY right!!! A bug had crawled into the tubing feeding the pressure switch, and had made a little nest of sorts in it. I used a small wooded skewer and cleaned it out, reinstalled the tube, and VOILA! I have heat again! Just wanted to let you know that your wisdom is still great! ;) Thanks!!

Dennis 11-20-2005 05:32 PM

if the gas is not turned on you will get the same 3 flash reading also.

portclinton 09-30-2009 08:32 AM

I had this same problem this morn and removed the front cover. noticed that there was water in the small flex tube going to my pressure relay. I removed all the water. (took a couple of tries). Then replaced bottom cover. I then started furnace and blew into the hose. I noticed that the heating element started to heat. Has been working fine for about 3 hours now. Will keep you updated.

jackley 01-17-2010 10:27 AM

American Standard 90
I just wanted to reconfirm this fix. My problem was calcium type build up. I cleaned what I thought was all the hoses but did not check the easiest one from the main unit housing to the relay unit. The build up was in the hard plastic piece on the unit. I cleaned it with a wire and shop vac and MAGIC! I was able to cancel my Sunday emergency call. Thank you!

moravac 02-03-2010 04:56 PM

American Standard Freedom90 flashing three lights
American Standard Freedom90 Single Stage; upflow; manufactured 2003
The furnace starts to work normally, but after 15min burners shut down and starts flashing three lights first than two lights.
There is white plastic box 4"x2"x1" close to the bottom on the right side (mine is upflow version) receiving 1/4" and 3/4" plastic tubing on the top of the box. 3/4" drain tubing is connected to the box on the side. I don't know what is the function of the box.
First I noticed water in 1/4" tubing and realized that the box is probably plugged and not allowing water to drain properly.
I removed the plastic tubing and unscrewed the box. There was some gunk in the box. I cleaned the box with plastic wire, rinsed with water and blow in the holes to make sure it is clear. I put the box back and connected the tubings.
Furnace is working fine for the last five days.

JohnH1 02-03-2010 05:16 PM

Im not sure what the question is. But if it is whats the white box it is a drain trap. It is there to prevent fumes from exiting the furnace as well as keeping air from sucking in allowing the furnace to drain properly.

beenthere 02-03-2010 11:17 PM


Originally Posted by JohnH1 (Post 394252)
Im not sure what the question is. But if it is whats the white box it is a drain trap. It is there to prevent fumes from exiting the furnace as well as keeping air from sucking in allowing the furnace to drain properly.

The original post is from August 2005

JohnH1 02-04-2010 08:54 PM


Originally Posted by beenthere (Post 394406)
The original post is from August 2005

I was trying to respond to moravac It looked as if he may have been asking a similar question to the oridginal post. O well

beenthere 02-04-2010 09:00 PM


Originally Posted by JohnH1 (Post 394947)
I was trying to respond to moravac It looked as if he may have been asking a similar question to the oridginal post. O well

I think he was just telling about his success at getting his to work again.


Earlcus 11-02-2010 11:57 AM

Flash code Or blinking red light 3 times
I had no ignition, but had the exhaust fan come on.
I checked out this post and it seems like you are dead on. After opening the access door. I unscrewed the access panel to the ignitor (two white wires connected it and it is were the gas pipe goes into the burner area) 5 screws, Unscrewed ignitor, (need ratchet for angle) :eek: cleaned ignitor with 600 grit sanding paper, reinstalled don't over tighten.
Took the vacuum hose off that went in the same direction as the gas supply, blew in air and put finger over hole were air was coming out. heard gurgling noise, and then sucked in and heard a back pressure noise and felt pressure. (did all three ends this way). Reattached.
turned gas and power back on, turned up heat and it ignited.
Don't know which one of these did it and since you are in there do them all. :thumbsup:
Hope this helps other too!

rmaj 01-09-2011 06:21 PM

draft pressure error- 3 flashes
We had the same problem 3 flashes showing a pressure switch problem. We took our upper and lower panel off and found the clear drain tube was full of water and a bug which caused alot of obstruction in the clear tube. We removed the tube and cleaned and dryed it out. After ,we reconnected the tube and replace the panels back onto our furnace. So far so good it is working great. We were so greatful for your posting as we lost heat on a Sunday with a low of 18 tonight.:)

pnj618 09-29-2011 06:38 PM

Same 3 flash code.
Hey guys,
just wondering if any of you could help. I have the same (American Standard Series 90) red light flashing 3 times. I bought and replaced the pressure switch as the inducer wouldn't even come on with the old one. I have blown out the vent, and cleaned out and washed all the hoses from the pressure switch, main housing condensation trap etc. When I start the furnace, the inducer comes on, blows for about 30 seconds. Then it just shuts off, and I am still getting the 3 flash error code. I know this is an old thread, but any advice you can give would be appreciated.

jackyboy 09-29-2011 08:46 PM

Same Problem same furnace...3 lights-a-flashing
I'm wondering where the pressure switch actually is. I see the white trap with 2 clear drain tubes going into it but it doesn't appear to be an electrical "switch" of any kind. Is the switch in the trap or somewhere else? Am Standard -Freedom 90 vintage 1996 High efficiency

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