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gotoman for ac
gotoman for ac, HVAC Technician
Category: HVAC
Satisfied Customers: 5206
Experience:  51 years of experience install design and repair of all makes and models of AC
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I have an Armstrong furnace thats about 10 years old. It

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I have an Armstrong furnace that's about 10 years old. It will not turn on at all, but the blinking light is blinking a healthy pulse. I verified power and checked the fuse on the circuit board on the bottom.

I checked the cutout sensor thing on the top with the red button and when I opened it (failed state) the fan kicked on but the burner wouldn't ignite.

So it's definitely got power and the blower motor works just fine. It seems like whatever is supposed to tell it to "kick on" isn't working. I changed the battery in the thermostat and even tried directly shorting the two leads that the thermostat connects to and nothing happened.
Russ here.. Try shorting between R and W at the furnace to see if it fires up. Make sure door switch is closed. Russ
Customer: replied 3 years ago.

Just did and nothing happened

You do have red light on board correct. Russ
Customer: replied 3 years ago.

If you're referring to the circuit board I didn't notice any red light. It does have power and the green light is pulsing healthy on the blue controller valve up above.

Fan does work in on position correct. Russ
Customer: replied 3 years ago.

I haven't tried the fan in the on position. I'll do that when I get home

Just to make sure we had control voltage to system. Russ
Customer: replied 3 years ago.

Yes, fan turns on and runs when I turn the fan on at the thermostat

See if you can see a model

number on gas valve. Russ

Customer: replied 3 years ago.

Looks like it's SV9520H8034.

I took some pictures of the various pieces. Let me know if you need more.


Circuit Board

Serial Number/Model Number

Gas Valve Model




Sorry site problems. According to flow charts you have a bad gas valve. Everything goes thru gas valve. Do you need source for new valve. Russ
Customer: replied 3 years ago.

ok, I don't have a specific place to get one. I do know there are a couple local shops in town to buy parts that I can call.

You can google that model number of valve and several sites will come up. If they do not have valve go to sites they are cheaper. Russ
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Customer: replied 3 years ago.

I just replaced the valve and it didn't fix it. It's still doing the same thing with the light pulsing green and happy and the furnace won't kick on.

please give me model number of fan board to check proper wiring for new valve. Russ

Customer: replied 3 years ago.

Hi Russ, sorry for the delay I had a pretty busy weekend. I hadn't messed with any of the fan board wiring, but your post got me to thinking that was likely the only place left.

We fortunately have two furnaces (upstairs and down) with the same board so I just swapped them between the two units. Sure enough, that was the problem and now the broke one is working perfect and the good one is now broke. I should be able to find one of these locally.
The board model is ST9160B 1068


I did notice on the bad board that it was very warm in the middle behind one of the circuits and on the good one it was cold to the touch. So I suspect something popped on it.


Unfortunately I had to pretty much destroy the old gas valve to get it off, so we did spend a little extra swapping that out, but even with that you helped me save a lot of money over a standard service call, so thank you very much for your help. :)

You are welcome . Russ