Sequence of events:
1 raise thermostat - furnace begins sequence
2 inducer fan starts
3 pressure switch closes
4 ignitor glows full hot, 5 seconds or so after, gas flows. ( it flows as soon as relay clicks - valve appears to respond OK ) about that time ignitor turns off. Sometimes gas ignites, more often it does not. Furnace will retry until it shuts down. Code light flashing single burst requiring a power off reset.

Questions:
1 how many seconds after ignitor starts should gas begin?
2 how long should ignitor stay on?
3 is this indication of a bad control board, if so can it be repaired or does it require replacement?
( PCBBF112S control board )

This is a indication that your flame sensor needs to be cleaned with steel wool or sandpaper. Some flame sensors look like this but yours could be different.

There is nothing wrong with the flame sensor. Go back and read the sequence of events again... the ignitor shuts off just as the gas begins. If I manually light gas, furnace stays lit, indicating flame sensor works.

Your quote: If I manually light gas, furnace stays lit, indicating flame sensor works.
Never in my life have I known someone dumb enough to light raw gas in a furnace. You are lucky you did not go boom. It must be natural gas since propane would have taken your head off.

You say (code light flashing single burst requiring a power off reset). If this is a constant flash look on the back of the blower door and see what it says.

Furnace fails to operate.
• Integrated control module
diagnostic LED is flashing

Continuously.

Polarity of

115 volt
power is

Reversed.

Polarity of 115 volt AC
power to furnace or
integrated control
module is reversed.

• Poor unit ground.

• Review wiring diagram to
correct polarity.
• Verify proper ground.
Correct if necessary.

• Check and correct wiring

There is a cure for this but it is somewhat unorthodox so I will leave well enough alone.

Ok let's start this over because we sure as heck aren't communicating.
The ignitor SHUTS OFF about when the gas STARTS. GAS DOES NOT IGNITE ( I believe you missed this point before you suggested flame sensor ) NO flame ever gets to see flame sensor. I apologise for not being more clear.
Forget about my lighting it... What I should have said is "if it starts on it's own it continues to operate, so flame sensor appears to work fine". After three unsuccessful attempts ( of it's own ) to start, the furnace shuts down and flashes. FAULT CODE 1 single flashes. A power off reset stops the flashing. ( from what I read the flashing for reversed polarity will flash all the time. Correct me if I'm wrong )

Here's how I see it. Glow plug is glowing when gas valve clicks,, this means flames should ignite right away,, but, just because the gas valve is clicking, doesn't mean its opening. Best way to test gas valve in this instance(since you know its getting voltage and clicking), is to hook up a monometer to outlet side of gas valve, to see if you are truly getting gas out of the gas valve. If you are on natural gas, you should get a reading of 3.5 inches of water colunm. Also, check inlet side of gas valve,, if incoming pressure is to high you will hear the valve click(like its opening) but the high pressure will not allow valve to actually open. Test the gas pressures and let us know what you find. I strongly suggest doing this before replacing the board,, only because you will kick yourself if you replace the board and it doesn't cure the problem. Good luck and please let us know what you find.

I thought you said it was flashing all the time. You did say single burst but I took that a single flashes like all the time single flash (continuous). Dang it. Jump through mygirlsdad77 instructions and post back.

OK fellas, I think we're getting somewhere now. One thing before I rig up a manometer though... the weird thing is if I place a long stem lighter tip right next to the gas outlet alongside the ignitor and light it when the itnitor lights , when the gas valve clicks I can hear the gas flow and the flame ignites immeadiately, I mean, no delay... click, hiss, light. So gas is flowing. It's just that at the exact time the gas valve clicks the ignitor shuts off. Sometimes it has enough residual heat to catch the flame, but mostly not.

If pressure is low that can cause the problem you are having. Look on the spec plate on the furnace for the exact setting.

Well I sure learned to be a whole more concice in describing a problem, sorry to lead anybody astray, both you guys are very helpful and I appreciate it. Well, looks like I'm off to the shop to throw together a manometer. Will report findings. KDKA

As luck would have it, I just had a call today on a Goodman gds80. Same symptoms as you are having,, igniter glows, then five or so seconds later gas valve clicked (and was opening as I checked all pressures in and out) only problem was, less than a second after gas valve opened, glow plug shut off. Called goodman and they said igniter should stay on for 5 to 7 seconds after gas valve opens. Which of course, is not happening on your furnace( and wasn't happening on the furnace I was working on). It actually takes about a second for gas to reach igniter from the time the gas valve clicks. This is why sometimes it will light, but usually not. So I put a new board in, and, bang, lights every time,, however, even with the new board, glow plug only glows for about three seconds after valve opens, but three is much better than 1, and is good enough to lite the burneres every time.

Here is my new take on this. I still suggest checking gas pressures on both sides of gas valve before getting a new board, as I have seen incorrect pressures cause this problem more times than not. Once you have determined pressures to be correct,, time to get a new board. How old is your furnace, the one I worked on was roughly a year old. Parts and labor were warrantied. One note,, even though the furnace was only one year old,, the replacement board was set up a little different,, it had all the same connections, but some of them were in different spots,, so if and when you replace the board, make sure to right down exactly what wires go to which terminals(markings, not location). Good luck and please let us know what the outcome is.

PS. The reason you were seeing a steady flash(diagnostic code) is this. The furnace in question will try three times to lite, if flame is not proven in three tries, the furnace will go into a one hour lockout(wich is shown on led as a constant flash.). After one hour, it will try three more times, and so on.

mygirlsdad77 news flash. The control boards are having a problem because some if not all the components are cheap china junk. One of the young men in the engineering class took home about 6 circuit boards for extra credit. He brought them all back to class within a week and all were working just fine. He discovered that many of the components were out of range especially the capacitors. He said good old RadioShack no longer has as many available parts anymore so he went to a electronic wholesaler that I deal with and charged them to my account (the little $hit)LOL. So now we will send the boards back to the mfg along with a large bill for services rendered. The biggest problem we face in this industry is not so much an engineering one but a bean counter one where they end up with junk parts because they are cheap. There are major differences in components of the same rate and the better ones cost a bit more money and if you want the really really good ones you get the military spec stuff for an extra 250% fee.

This can be the difference between a 7 second glow delay and a 3 second glow delay if you follow my drift. When a component changes value right in front of your eyes on a meter you know something is wrong with that picture.

We just purchase our control boards and other parts from our goodman supplier, assuming they are sending us factory goodman replacement parts. I just assumed they had reconfigured their board(very small change, heat term and cool term for blower were switched.). We don't use universal boards on any of our furnaces, only factory boards, unless its an old out of date furnace that requires a universal board because the original board is no longer in munufacture.

These boards were sent in warranty defective for us to figure out what was wrong with them. I always suggest using the factory board designed for the exact unit model number other wise if something happens the installer/company could be held responsible if you know what I mean.

I'm glad you fellas see what my problenm is now. Only my ign shuts off at the same time the gas relay throws. Sometimes gas will catch, but most of time not. Well, I didn't have any tubing out in the garage, and I'm busy tonight. Tomorrow I will see how many inches of water I get from the thing, which by the way it's now on it's third winter. I figured all along that perhaps a cap or resister on board changed value or went dead and the timer chip no longer sends correct events. Another theory I have is possibly gas relay is pulling current down enough to cause ign relay to drop out. ( since it appears tp happen simultaneously -of course things are happening so fast, I would rather record events on a strip chart. But for purposes here I can definitely say that it is far less than a second ) looks like it's time to study the schematic. Fortunately I'm a tech at an aerospace avionics radar/ comm radio mfr. If the gas pres is OK and board is bad, believe me it's going to work for a thorough troubleshooting... it just pisses me off to no end to pay for a new bd. When it may be easily repaired. Will keep you posted.. . pressure results coming tomorrow. -KDKA

Have you tried cleaning the flame sensor. If it does not sense flame it will shut down the unit in short order. They are very sensitive to having a coating collect on them causing a problem. See below

Quote:

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Originally Posted by hvac1000

These boards were sent in warrenty defective for us to figure out what was wrong with them. I always suggest using the factory board designed for the exact unit model number other wise if something happens the installer/company could be held responsible if you know what I mean.

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Im with you on this 100%

The results are in: 6.75" wc in / 3.375" wc out.
-KDKA

Inlet is good, but you need to bump manifold side up to 3.5, Most likely won't cure your problem, but needs to be done anyway.., I'm convinced you need a new board. Good luck and let us know how you make out.

FINAL REPORT:
Instd' new board. Worked fine for a few days, then problem returned intermittantly. So I looked at pres. sw. a lot more closely. It closes, but no completion of circuit!
Replaced switch and now everything works fine... including the original CB.
Thanks to hvac100 and mygirl'sdad77 for all the assistance. KDKA over and out.