Need help diagnosing Amana 90 3x blinking error


  #1  
Old 11-14-13, 07:36 PM
B
Member
Thread Starter
Join Date: Nov 2013
Location: Canada
Posts: 5
Received 0 Votes on 0 Posts
Exclamation Need help diagnosing Amana 90 3x blinking error

Hello,

We have an Amana AMV90704CXA furnace which services our second floor that started to act flaky about a week or so ago. It began by not keeping the set temperature and was only turning on for about 5 minutes (with hot air blowing) once every 12 hours or so. It's around 32 F / 0 C outside at the moment and the first floor furnace (same make/model) is working properly.

Because the furnace was running every once in awhile, I thought the thermostat might be bad; so I tried installing a new one, but there was no difference. I then went down to the basement to look at the furnace itself.

At the furnace, the circuit board red light is steady when no request for heat exists. When I turn up the thermostat, the red light goes off and then continuously blinks 3 times with no further response from the furnace. The error code on the inside of the door says that the “low fire pressure switch is stuck open”. After I changed out the thermostat, I have not heard the upstairs furnace run at all, so I'm guessing what started off as an intermittent issue has turned into a chronic one.

After doing some web research, I've tried a few things, but nothing has changed. Here is what I've done so far to try to remedy the situation:

1. Re-installed the old thermostat with new batteries.
2. The fan/blower works when I change the thermostat setting from “Auto” to “On”.
3. Checked the air filter for blockage, filter is clean.
4. Powered the furnace on/off numerous times (waiting at least 30 seconds in between).
5. Powered on/off the gas valve switch a few times.
6. Cleaned the flame sensor with fine emery paper.
7. Blew and sucked on the hose from the inducer to the high/low pressure switches to check for leaks. Could hear switch(es) move/click, did not detect any leaks, no water or debris in hoses.
8. Inspected the condenser pressure switch hose for leaks, none detected.
9. Inducer spins freely, blew into inducer hose connection from the pressure switches, no resistance encountered . The inducer motor is not starting when requesting heat.
10. Checked the condenser hoses to the drain for blockage; saw that water is moving freely out of the drain hoses.
11. Checked the outside vents for blockage, none found.
12. Disconnected the intake pipe on top of the furnace and checked for blockage, none found.

I have a multimeter, but I'm not very proficient with it. I'm confident that I could put it to good use with some additional help/guidance.

My uneducated guess is that either the circuit board, inducer motor or the low pressure switch needs replacing, but since I'm currently unemployed, I don't want to invest $ without knowing what to replace to fix it. I was hoping that it would be a quick fix, but at this point I just want to find out what's wrong and get it working again before the deep winter temps arrive (or before my wife "kills" me for being too cold - if I can fix it myself, great; otherwise I'll call a pro). Any help with further troubleshooting or diagnosis would be greatly appreciated.

This is my first attempt at fixing a furnace, but I built up my DIY mechanical courage by successfully rebuilding our garage door opener this past summer.

Thanks in advance!
 
  #2  
Old 11-15-13, 10:28 AM
B
Member
Thread Starter
Join Date: Nov 2013
Location: Canada
Posts: 5
Received 0 Votes on 0 Posts
Question New symptoms / circumstances - hopefully more clues

A very strange update today: the furnace started running this morning without me doing anything. It has kicked on about three times for about 5 minutes each time blowing warm air for nearly the last hour and is holding the temperature set on the thermostat. I'm assuming I can take the inducer motor off of my list of suspects; that leaves the circuit board or the low pressure switch. Am I right or am I missing something?

No recent activity for the past few minutes, so I just checked the furnace again and it is 3x flashing red as previously. Any ideas out there?
 
  #3  
Old 11-15-13, 02:10 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 70,036
Received 2,944 Votes on 2,657 Posts
That is a two stage heating furnace and has a low pressure and a high pressure switch. The low pressure switch is not closing when the draft inducer starts. Did you check both pressure switches ?

Amana-hac. Portals_pdf_AMV9
 
  #4  
Old 11-15-13, 05:00 PM
B
Member
Thread Starter
Join Date: Nov 2013
Location: Canada
Posts: 5
Received 0 Votes on 0 Posts
Red face Thanks for the reply!

Hello PJMax,

Thanks for the suggestion.

Looking in the top section of the furnace, there are 3 of these switches; 2 interconnected on the right and 1 standalone on the left.

How do I go about "checking" the pressure switches?

I'm embarrassed to have to ask, but I'll need some step-by-step guidance here.
 
  #5  
Old 11-15-13, 05:25 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 70,036
Received 2,944 Votes on 2,657 Posts
The low pressure switch should have a red and blue wire on it.

You can check it with an ohmmeter. Take one wire off. Connect your meter to the two switch contacts. There should be no resistance (no meter movement). Set the thermostat to call for heat.... the ohmmeter should now show a low resistance... basically a dead short.
 
  #6  
Old 11-16-13, 01:29 PM
B
Member
Thread Starter
Join Date: Nov 2013
Location: Canada
Posts: 5
Received 0 Votes on 0 Posts
So I did the check with the digital multimeter. Without doing any testing, when I switch the multimeter to resistance, I get a reading of 1 and when I touch the 2 multimeter leads together, I get a reading of 0. I'm assuming this is proper operation.

The low pressure switch has 1 red wire lead connector and a 1 blue wire & 1 grey wire lead connector. When I tested each of the 3 pairs of switch contacts, the multimeter does not change from a reading of 1. I tried it a couple of times with each switch and got no change in reading from the multimeter.

Again, the furnace was running on its own every once in awhile this morning, but right now its just the 3x blinking red light.
 
  #7  
Old 12-11-13, 09:36 PM
B
Member
Thread Starter
Join Date: Nov 2013
Location: Canada
Posts: 5
Received 0 Votes on 0 Posts
Angry New information, what now?

An update on the freaky furnace. Two weeks or so ago, the furnace started running normally for about a week. After that week, it quit again. This time it was showing a 2x flashing red light, which supposedly means the low pressure switch is stuck closed. I tried restarting the furnace with a power off/on and it would run as expected for one heating cycle and then stop after the thermostat calling temp was reached. When it tried to start after the temp dropped below the thermostat setting, it would throw the 2x flashing red error light and the inducer motor would continue to run.

After a week or so of not getting any further input from the forum, I called in a service guy. I told him what I had done and after doing some brief testing, he was quite convinced it was the low pressure switch. He said he would pick one up and get back to me. A week later, I did not hear back and it has been very cold here. I called him late last week and he said he would drop it off to me on Monday. With no response by Wednesday, I decided to try to source one myself. So I picked a new one up today (combo high and low, exactly what was originally installed) and carefully replaced it without issue using a photo of the original setup to make sure I had the wires in the right places.

Unfortunately, there is no change in the furnace behavior. After one complete cycle, it still throws up the 2x flashing red light and the inducer motor continues to run. I've since turned the furnace off; I didn't think it was a good idea to continue to let the inducer motor run (or am I wrong?). My guess is that I can't return the pressure switch, since it is an electrical component. So I'm an unhappy camper, out $95 with no solution.

Any ideas out there? Any suggestions would be greatly appreciated.
 
  #8  
Old 01-07-14, 06:41 AM
S
Member
Join Date: Jan 2014
Posts: 1
Received 0 Votes on 0 Posts
I have the same furnace with very similar issue flashing 3x light. It doesnt light the ignightor. Ignightor is good and was just replaced 1 month ago. Hoping you will see this and have a resolution as its currently -12 deg here in MI.

Other things I have found.

I unplug the ignightor(did to test it) and then it will cycle 1 time

When I got it to cycle this morning, I turned it off in the middle before it reached thermostat temp and it lit again when I turned it back on. But it kicked off before reaching thermostat temp and now wont kick on again. Still flashing 3x and inducer still running.

Need Some help
Thanks in advance
 
 

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