Amana/Goodman furnace odd issue

[Robert Adams]

Messing with a 2 stage one that has 9 blinks.... It will go through it's self test at power up and then start blinking and will not try to start the furnace. When I unplug the ignitor all is right with the world at power up it just doesn't have an ignitor to start the flame. Now what's odd is that it is showing just over 40 ohms...  

      Can't find anything else wrong with it so unless I'm missing something I will pick one up tomorrow. Any thoughts on what I might have missed. I did commercial refrig many years ago and gas furnaces were not on that list of things to do.

[Phil Thien]

How long has it been in service?

[Robert Adams]

How long has it been in service?

         About 6 years or so.

[Phil Thien]

http://www.weinstall.ca/furnace-error-co...codes.html

You checked the pressure switch hose?

Somewhat interestingly, I had one of the lower-end units installed in a retail space and the pressure switch hose was supposed to be cut to final length by the installer, such that there were no sags.  They didn't, and water collected in the sag until the unit wouldn't fire.

It doesn't take much restriction in that hose to prevent operation.

[Robert Adams]

Yup checked it all however the fan would never turn on so the pressure switches were a moot point. Once I unplugged the ingitor it finally starting working right. Other than not having an ignitor plugged in to light the flame.

[Phil Thien]

Yup checked it all however the fan would never turn on so the pressure switches were a moot point. Once I unplugged the ingitor it finally starting working right. Other than not having an ignitor plugged in to light the flame.

Whelp, looks like that is the next logical step.

Any way to measure the terminals to which the igniter are connected, to see if it is trying to spark?

[Robert Adams]

Whelp, looks like that is the next logical step.

Any way to measure the terminals to which the igniter are connected, to see if it is trying to spark?

      Can just check the voltage at the ignitor leads. It's a hot surface ignitor and they are traditionally known for short lives... I didn't bother checking as after I unplugged it the error code went away and the furnace started to go through it's normal start up routine. Morrisons was out of them but they will have one there in an hour or so. 

The old one may have a slight short to ground or have too little resistance when power is fed through it and the board says it's bad. Corneilius ice machines used to do the same with the IR sensors on the ice doors. The board would register them as closed to restart the cycle but it wasn't quite enough continuity for the chip to actually start. Even though the LEDs on the board showed the sensor as working...

     If I were building a house from scratch I would have a mechanical room and two hvac systems on tracks. If one shuts down you can pop off the feed and return duct and have disconnect on the thermostat. Then roll the broken one to the side and the spare in place. And I would have a stockpile of spare parts as well. FYI some HVAC components are getting hard to get recently. Boards for some units are backordered for months so you either improvise with a generic board or.... Stick with the simple HVAC systems since parts are cheap and available ie common...

[blackhat]

So, what does the unit literature say a 9 blink code is?  I had a unit recently that would cycle right up to energize igniter. As that relay on the board closed, voltage on the board would drop until the board cycled off and restarted. This drop and restart was happening in fractions of a second. The igniter was fine, the board was not throwing a diagnostic fault code.

[Robert Adams]

So, what does the unit literature say a 9 blink code is?  I had a unit recently that would cycle right up to energize igniter. As that relay on the board closed, voltage on the board would drop until the board cycled off and restarted. This drop and restart was happening in fractions of a second. The igniter was fine, the board was not throwing a diagnostic fault code.

         The code says... 
           Input polarity reversed. It is correct. 
      
           Also says L1 on board should read 115v to neutral and ground and neutral read 0 to ground which it does.


           It will trip the code at self check as soon as it closes the relay for the ignitor. If you leave it unplugged it will go through everything as usual crank the fan open the gas valves then error since it isn't lighting. 

           They let me borrow a board to swap out and same issue with a new board as well. I haven't a clue what it would be now.

[blackhat]

Odd one. Last time I had a similar issue on a Goodman, a board replacement corrected it. Have you tried an igniter replacement?  40 is pretty low and would throw a pretty high draw on the board.