Amana GULA090AX50 Furnace - Furnace starts then stops

[_Carl_]

Ok so I was told to start my own thread here after posting 6 times on a 6 year old thread that had a similar issues and a similar model of furnace..so below will be all that transferred over here.

 

Post 1:

The following was quoted from applianceman18007260692

"Continuous flashing on the LED might mean your furnace has a reversed polarity of 115 volts. Turn off the power and correct the wiring polarity after reviewing the wiring diagram"

 

 

I have an amana gula090ax50 using propane, doing the same thing..flashing the red led continuously.The furnace tries to light, the burners come on then go out, this will happen 4 - 5 times then it stops completely..at this point is when I seen the continuous flashing led on the main board. How does the polarity get reversed in the first place ?

 

Here is a chronological order of event since problems started:

1 About a year ago the burners would try to light then go out and blower would just run continuously with no heat. ( repair man tapped the pressure switches with a screw driver) it worked after this. He said they get stuck sometimes and I eventually would have to replace them. 

2. Recently ( two weeks ago) the furnace started to go out as soon as the burners come on but would always work after the second try.

3. I tested the pressure switches and they both had 24v to them. I tested the primary automatic limit switch and it had no continuity. I replaced the limit switch and it started working normally again for the last two weeks until this morning at 3am and -18 f outside  

4. When I replaced the limit switch the blue wire was on top and the other wire was on bottom, but when I got the new switch it was shaped a bit different..I couldn't see any marking on either switch to represent a + or - side. A tech on YouTube told me the wire orientation on the switch didn't matter but now I'm wondering if maybe this is the cause of my reverse polarity ? 

5. I turned off power to the furnace and switched the wire position on the limit switch to see if that would change anything and the furnace light up and stay on working normally...so far.

6. When I had the multimeter on one pressure switch I did see a large voltage drop but I may have moved the lead off slightly as its hard to keep it in place due to the terminal being up inside the switch slightly. I was going to unscrew the pressure switch from the furnace to get a better angle to test it but didn't because I'm not sure if being screwed to the furnace is acting as its ground ( I guess I could just rest it on the metal housing on the furnace ? ) should the pressure switches be getting 24v all the time or just during a certain sequence ?

7. I am going to try taking off the hoses to the pressure switches and blow though them to see if any blockages ( not blowing into the pressure switch , I know this will ruin them) and also check the orifices they are attached to for any crud there blocking air flow.

Anyone have any ideas ?

 

Post 2:

Switching the wires didn't seem to work although after trying about 5 times it did come on and is currently blowing heat.

 

during the summer my propane company replaced a part on my propane tank ( the main valve with the vent on it)..is it possible they didn't set the pressure high enough..would low gas pressure cause issues like this ?

 

Post 3:

hoses were clear. 

I noticed this time when the 4 burners light up the far left one was having trouble but finally came on. Indication of low gas pressure ?

 

Post 4:

After further testing I think I've figured out the left pressure switch is bad based on the following data: (someone please double check my method of testing)

multimeter positive lead connected to one of the two terminals on pressure switch  (with furnace wires still connected) , negative lead to a solid ground.

 

Right Pressure Switch:

maintains 26.5 - 26.9 v during initial starting sequence (never fluctuated beyond this)

when burners light up it drops to 24v and stays there...seems normal.

 

Left Pressure Switch:

fluctuating voltage during initial start sequence  0.15 v - 00.0v - 24.6v (burners try to light)- 7.6v - 0.00v - 24.6v (burners try to light) - 00.0v - 24.6v(burners try to light) -00.0v

 

I will refer to the experts here, but I'm think this proves a left pressure switch is at fault ? if so I will replace both since the other is probably not far from failure too.

 

Post 5:

I forgot to mention something,  I noticed there is now a slight gap between the lower unit of my furnace and the upper part by maybe 3/8 of an inch, I can now see the little lip on the lower unit where the upper unit rests against it. The caulking that sealed the two together is now opened up.  It looks like the floor where the furnace is located has settled on me. 

I wanted to mention this after reading this "Any leaks in the heat exchanger or your combustion chamber could cause a weak negative pressure at the draft inducer housing port."

 

Post 6:

I also just removed each switch from the furnace to test for continuity, neither switch has continuity.

 

The reason I checked for this is after reading the following from RepairClinic  - Most Frequent Causes for Furnace starts then stops Cause 3Pressure Switch

"The pressure switch closes when the burner has sufficient airflow. If the pressure switch isn’t working, it might not close when the proper airflow is present, causing the ignition process to stall. If the ignition process stalls, the furnace will shut off. To determine if the pressure switch is defective, use a multimeter to test the switch for continuity. If the pressure switch does not have continuity, replace it."

 

Ok that's it, I'm all caught up on my own topic... hopefully now I can get some help since its 3 degrees f outside and I'm running low on wood 

 

 

 

 

 

 

[AccApp]

Can you post some pics at a third party hosting site and link to them here? I don't think all your wire switching could have caused a reverse in polarity. I think the continuous flashing of the red light indicates a "Lock out" condition where the board won't attempt ignition. Check all the hoses leading into the pressure switches, make sure they are clear and then make sure the switches activate when suction is applied. I'd also remove the flame sensor and give it a good sanding with whatever strip of plumber's abrasive I had handy, some like to use steel wool.

[AccApp]

Is there an error code chart attached to the furnace? Sometimes it's on the blower access door or inside the blower access door.

[_Carl_]

I had already checked the hoses ...

Post 3:

hoses were clear. 

 

You say to  "make sure the switches activate when suction is applied"  how exactly do I do this ? I was told sucking or blowing on the pressure switch can ruin them very easily.

and what pics specifically do you want?

 

here is a link to picture of my error code chart..don't know how I missed this on the blower access door panel. 

Amana Model GULA090AX50 Error Code Chart

 

[_Carl_]

As far as the error code flashes,  I remember it would flash then I would count 3 seconds until the next flash and it did this continuously.

[AccApp]

1 minute ago, _Carl_ said:

As far as the error code flashes,  I remember it would flash then I would count 3 seconds until the next flash and it did this continuously.

That's a 1 flash error code, were you able to locate the error code chart?

[AccApp]

Just now, AccApp said:

That's a 1 flash error code, were you able to locate the error code chart?

yup, lockout, ignition tries and failures exceeded.

[AccApp]

I've never heard that blowing or sucking on any pressure switch will ruin it.

[_Carl_]

yes, the error code pic I left already above

 

Also I had already cleaned the flame sensor with steel wool before I posted any of this.

[_Carl_]

what about the fact I have no continuity for either pressure switch ? like i said I read on  RepairClinic  - Most Frequent Causes for Furnace starts then stops Cause 3Pressure Switch

"The pressure switch closes when the burner has sufficient airflow. If the pressure switch isn’t working, it might not close when the proper airflow is present, causing the ignition process to stall. If the ignition process stalls, the furnace will shut off. To determine if the pressure switch is defective, use a multimeter to test the switch for continuity. If the pressure switch does not have continuity, replace it."

[_Carl_]

Here is the information I found on sucking on pressure switches and it can damage them:

source: advising not blowing on pressure switches

I've also seen several YouTube videos from hvac pros advising not to blow or suck on the switches because it can damage the diaphragm inside.

also I tested the voltage like it says from that link which I had posted the results above. but sum that test I got random voltage on one pressure switch and no continuity on either of them.

[_Carl_]

My answers to the following potential issues are in bold 

A gas furnace pressure switch problem could be caused by the following:

• Your vent could be stopped up with a bird’s nest, wasp nest or debris. 
• I checked this and is not the case 
•  
• You could have a bad, dragging, dirty or slow running draft inducer.
• not sure how to fully check this, but seems to be running normally
•  
• The tube that runs from your pressure switch to the draft inducer could be plugged up. Many times the tube is plugged up with water. If the pressure switch tube has water in it then this is a sign that you condensate drain line could be stopped up or not draining properly. You can disconnect the pressure switch tube and run a wet vac to hopefully clear the stopped up furnace condensate drain line.
• No water or debris was present when I blew the hoses out
•  
• The draft inducer hole could be plugged up. I have seen the draft inducer holes get stopped up so bad that I had to use a small drill bit and drill to open the hole back up.
• if this hole is the one that connects to the draft inducer from the pressure switch tube..it looks to be clear
•  
• On high efficiency condensing furnaces the water drain line could be stopped up, causing a water back up and blockage in the pressure switch tube
• I'ts not stopped up

[AccApp]

37 minutes ago, _Carl_ said:

Also I had already cleaned the flame sensor with steel wool before I posted any of this.

Try it with some plumber's cloth, the steel wool might not be getting the corrosion off. If it was a pressure switch issue, the gas valve would never open and you wouldn't get a lockout after so many attempts.

[_Carl_]

its looks very clean to me but ill pull it off and try cleaning it again..I only have sand paper and 000 steel wool..I live a ways from town or I would go buy plumbers cloth and try it.

before I read your last post I was in the middle of trying this method to test the pressure switch  How To Test a Gas Furnace Pressure Switch I'll post back here in a few minutes the results.

Also I will clean the flame sensor again..I seen a pro say not to use something to abrasive or you can scratch it and shorten its life..he even use a crisp 5 dollar bill to clean it as can be seen here https://www.youtube.com/watch?v=tYwR9qL4lnk

I think I have some 400 grit sandpaper would that be ok to use ? or what grit would be safe to use?

 

[_Carl_]

After this test http://www.hvachowto.com/2015/10/26/test-gas-furnace-pressure-switch/

I believe you are right about the pressure switch as both have continuity when the inducer motor kicks in and pulls vacuum..but why does one switch have normal looking voltages and the other switch way different voltage readings ? as seen below :

Right Pressure Switch:

maintains 26.5 - 26.9 v during initial starting sequence (never fluctuated beyond this)

when burners light up it drops to 24v and stays there...seems normal.

 

Left Pressure Switch:

fluctuating voltage during initial start sequence  0.15 v - 00.0v - 24.6v (burners try to light)- 7.6v - 0.00v - 24.6v (burners try to light) - 00.0v - 24.6v(burners try to light) -00.0v

 

Now I'll go re-clean the flame sensor

 

[_Carl_]

I re-cleaned the flame sensor much more thoroughly than I did the first time with 000 steel wool and got it as clean as it can be..looks like new now.

The furnace fired up all burners right away light and is blowing heat. Ill post back as it cycles more times to see if its is consistent. 

I would have done this flame sensor test How To Clean And Test The Flame Sensor but I don't have a multi-meter that has  milliamps or micro-amps 

[AccApp]

Don’t over think this. Chasing bizarre voltage readings, etc will just waste your time. If it’s running consistently just let it run until it stops again.

[_Carl_]

Gotcha.  Ill post back tomorrow the results of it running tonight. It will be -16 degree f tonight so I'm sure it will be kicking on quite a bit.

[AccApp]

That sounds cold

[_Carl_]

got so cold my water pipes froze up last night so ill also be dealing with that today.

 

..and the furnace is still doing the same thing 

[_Carl_]

Here are some pics of the furnace where I mentioned earlier :

"I forgot to mention something,  I noticed there is now a slight gap between the lower unit of my furnace and the upper part by maybe 3/8 of an inch, I can now see the little lip on the lower unit where the upper unit rests against it. The caulking that sealed the two together is now opened up.  It looks like the floor where the furnace is located has settled on me. 

I wanted to mention this after reading this "Any leaks in the heat exchanger or your combustion chamber could cause a weak negative pressure at the draft inducer housing port."

would this gap be considered a leak in the combustion chamber ?

 

pic 1 of furnace gap

pic 2 of furnace gap

pic 3 of furnace gap

pic 4 of furnace gap

[AccApp]

You have a furnace-matched cased Air Conditioning cool above the furnace. The joint between the furnace and the coil case is opening up for some reason. That shouldn’t affect your heat exchanger at all.

[AccApp]

Try giving the flame sensor a good cleaning down to bright, shiny metal.

[AccApp]

I’ve even used a utility knife to scrape one in a pinch

[_Carl_]

I will try again..I'll post a pic afterward to show how clean it is..hopefully the camera will show it accurately..also I did test it for continuity and it passed.