Hello,

I am having an issue with the following HVAC System:

Amana
80% Gas Furnace
GUIA090A50
P117305F
White Rodgers 50A50 Internal Ignition Control
Split System

Air circulation blower and induced blower will run continuously even after thermostat is turned off. Observation window indicates a continuous light flashing and according to manual is considered "Flame Sensed with no call for heat". Probable cause is listed as either a short to ground in flame sense circuit or miswiring. System was working fine until yesterday. Circuit board was replaced November 2010.

Since heating system was working all winter and AC up until a few days ago I do not think it is miswiring so what exactly is a short to ground in flame sense circuit and can I fix this myself? Would it help if I cleaned the flame sensor? Is there any other cause for this? Any assistance is appreciated and thanks in advance for your help.

Usually a single continuing flash means one hour lockout. Could very well be caused by a dirty flame sensor. Start by cleaning the flame sensor and post back with results. One step at a time here, okay?

Thanks for responding and understood. This morning I unplugged system to stop blower and plugged it back in when I got home and it started blowing again. Right now covers are off unit and I have cleaned flame sensor. Will taking off the covers for one hour unlock the system?

Killing power to the unit for a few seconds and powering back up should reset the board. Watch it as it starts up and tell me exactly what sequence things are happening in. The more detailed info the better I can try to help.

I will say, the fact that the blower and draft inducer are both running makes me think you have a tripped limit, or rollout switch. Check all rollouts and limits to see if they have a small button in between the wire connections that can be pushed in to reset. Main limit won't have a manual reset, so lets skip that. You are looking for a secondary limit which would be located near or on the blower housing. Also, flame rollout switches which would be located on the top or bottom of the burner assembly.

Unplugged unit. Plugged unit back in. Red light on circuit board comes on for a second then goes off. Clicking sound. Red light comes back on and starts flashing and blower starts.

Does the draft inducer run? How much time before the blower starts to run.

Count of seven until the blower comes on. I can definitely see and hear the blower (located above filter) and I can feel the inducer working. Located flame rollout switch inside burner assembly and auxiliary limit. I could not reset either.

With the guidance you supplied I reviewed the service manual and located sections pertaining to servicing primary limit control, auxiliary limit control, and flame roll out control. I am going to purchase an ohmmeter tomorrow to test and will post results.

Sounds good. Let me know what you find. Also, check to make sure the pressure switch is closing when the draft inducer starts up. We will get this thing yet (hopefully). It could be a bad board, but its better to eliminate everything else before replacing the board.

If I am operating the ohmmeter correctly then all (primary limit control, auxiliary limit control, flame roll out control, and pressure switch) tested fine. Next steps?

Quick question. It will be around 105 where I am at tomorrow. Can I still operate the AC without further damaging the system?

Sure, if the a/c works, it will be fine to operate it.

As for the heat, reread the diagnostic light section. Let me know exactly what it says for a steady blink, or whatever sequence of blinks you are getting.

Ran AC this weekend (Saturday) and it worked fine even with blower and inducer malfunctioning. However there was a positive and negative side effect. Positive effect is blower and inducer issue corrected itself. They no longer run continuously and there is no flashing light. Negative effect is Sunday morning the AC stopped working at all. All I get is a humming sound coming from the unit. Capacitor top is bulging and I am going to replace today.

As to the error I was getting the sequence of lights (continuous flashing) is considered "Flame Sensed with no call for heat". Probable cause is listed as either a short to ground in flame sense circuit or miswiring.

Should I be worried about the negative effect or chalk it up to coincidence? Could the capacitor be the cause of the problem?

Sounds like coincidence? Problem in the furnace won't cause the capacitor to fail. But, since the cap is bulged, it is most likely bad (almost definately). Replace the cap, and you should at least be back in a/c. As for the heat, it may just be time to get a tech in there to check things out. Nine times out of ten, the code you are getting indicates a bad board, but its always best to have things checked first. Usually the short to ground in the flame sense circuit is in the board, so a new board it would be. However, like I said, I hate to replace boards without knowing for sure. Good luck, and please let me know how things work out. One thing you can do is to take a real close look at the board, front and back and see if there seems to be any burn spots, or corrosion. If so, even more reason to suspect the board.

Replaced capacitor and AC working fine. I will check the board for burns but otherwise system working aa it should. Thanks for all of your guidance and assistance. I truly appreciate it.

Glad to help (if I did?). Glad to hear the a/c is up and running again. Take care.