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airheatman
airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8259
Experience:  Furnace, A/C and heat pump specialist.
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I have a furnace that will blow air but not heat it. There

Customer Question

I have a furnace that will blow air but not heat it. There is an E2 code flashing on my unit (Amana - about 5 years old). I changed the filter (old one was not plugged with dirt) and still get the E2
JA: Did you double-check the thermostat's settings? And what about the filters?
Customer: I put in a new filter without any improvement. The thermostat (Ecobee) is set to heat and has a setpoint of 67. It is 63 in my house.
JA: Do you plan on doing the work yourself?
Customer: If it's within my troubleshooting skills.
JA: Anything else we should know to help you best?
Customer: Furnace and Thermo have been working fine for several years, no recent changes. I did lose power (entire neighborhood) shortly after I discovered the furnace issue. Maybe there was an intermittent power loss earlier in the morning.
Submitted: 9 months ago.
Category: HVAC
Expert:  airheatman replied 9 months ago.

What is the model on the unit and is the error on the unit itself?

Customer: replied 9 months ago.
Amana AMVC8090SC
Customer: replied 9 months ago.
The error is E2 displayed through the peek hole
Expert:  airheatman replied 9 months ago.

The E2 is an open pressure switch error. Does the inducer vent motor come on. (Turn power off to furnace, then back on and call for heat, see if inducer fan starts)

Customer: replied 9 months ago.
Here is what happens. I turn power back on the unit (AMVC80805CX) and the green light flashes and the code OP is showing. All looks good. Then the thermo demands heat and two cycles of 'clicking' / LO display / 5 display occurs in less than a minute, then the blower starts up and the E2 code displays.
Customer: replied 9 months ago.
Update. The codes 'LO' and 6 cycled in the LED. this time it seemed to work. The pilot ignited the gas and the heat chamber heated up. I'm going to button up the unit and test it again.
Expert:  airheatman replied 9 months ago.

The OP is normal operation

The LO indicates unit is operating at low stage heat

If we get the E2 that is indicating inducer motor is not drawing sufficient vacuum on pressure switch.

Let me know and we will go from here as needed.

Customer: replied 9 months ago.
Well with the front panels back on the unit it failed the first time, it's back to the 'LO' & '6' then E2. I cycled power and this time the flames fired up - I can hear the vortex sound and the stack is getting hot. There is heated air coming out of my vents now.
What do you recommend for further troubleshooting?
Customer: replied 9 months ago.
After 4 minutes of running with heated air, the E2 code came back and flames shut off
Expert:  airheatman replied 9 months ago.

I would make sure there are no obstructions in either intake or exhaust vents.I have see as small as a spider web effect vacuum .Next make sure hoses from inducer to switch are not kinked or cracked

Remove hoses and clean and clean fittings where they connect to switch and inducer with a straightened paper clip. Then make sure main drain is flowing freely with no water backing up in hoses.Make sure all wiring is making good connections at switch and control board.

Beyond that you will need to call in a tech with a manometer to test and determine if the switch is bad or if the inducer is the issue not pulling sufficient vacuum on the switch.

Customer: replied 9 months ago.
Questions.
I have a PVC pipe drain line that is closed all the way to the floor drain. I shake it and it doesn't feel like it has water trapped in it. Is that a good test?
Also, is the inducer motor attached at the bottom of the exhaust vent? I see a motor with two pressure switches? that have clear tubes joining into a single (teed) and then into the chamber that the motor/blower is serving.Should I also get on the roof and check the vent up there?
Customer: replied 9 months ago.
Your are referencing hoses twice in your instructions. Water should be found only in the drain hose while the inducer hoses have air. Correct?
Expert:  airheatman replied 9 months ago.

Sorry for delay.Been trying to find some pics. The hoses from inducer to pressure switch should have air only. Drain hoses should have no standing water except in trap and main drain going outside should have no standing water.

Expert:  airheatman replied 9 months ago.

Not finding very good pics. This one shows the hose which should have no signs of water. And shows how to check vacuum with a manometer. You could remove the hose from swich and after inducer starts suck on hose and see if furnace will stay running.That would indicate an issue with inducer not pulling enough vacuum.

Customer: replied 9 months ago.
I seemed to have fixed the issue, will test how it goes overnight. During the heat demand cycle, I saw E2 again so I started removing/replacing the vacuum tubes between the pressure switches and the inducer chamber, and wiggled the pressure switches. The heater kicked on and ignited the gas and heated for 15 minutes (i had the setpoint 3 degrees above ambient.
So I buttoned up the covers and ran the test again, good result. Why are there two pressure (vacuum) switches tied to the inducer chamber? Redundancy? Or is there two setpoints being monitored?
Expert:  airheatman replied 9 months ago.

One is for low stage and the other is for high stage

Customer: replied 9 months ago.
Ah that makes sense. Low stage is during the pre-ignition phase, while the inducer blower is clearing out the plenum from any vapors and hi stage is during heating/flames. When I read low stage with the E2 error, I was thinking physical, like low area of the furnace, the filter area. Each of those two pressure switches have unique pressure set points. They fail open to shut down the unit.
Expert:  airheatman replied 9 months ago.

That is correct

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