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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