# Furnace issue



## Sparkylu38vb (Nov 27, 2013)

I have an Armstrong ultra sx 80 furnace. Having two issues that may be related. Unit cycles on and off when heating to 68, it's not really a short cycle, unit runs for approx 7-10 min shuts off for split second then restarts immediately and repeats. Maybe this is normal for this unit?

The other issue is I recently installed a new Honeywell smart stat that requires the common wire ( old stat was batt powered) screen intermittently goes blank as if losing the 24 volts. Is this a transformer problem or a board problem?


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## PrestigeR&D (Jan 6, 2010)

Throw a meter on it,,,,,narrow it down....

If you didn't have any problems up until you replaced your old thermostat for the new one you have,,,

It may be your thermostat ,or something else,....narrow it down,,,,



JMPOV,


B,


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## Sparkylu38vb (Nov 27, 2013)

Had same cycling issue with old stat. First thing I did was to put meter on everything, getting 24V. Since the stat issue is intermittent was wondering if anyone heard of this being a possible board issue.


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## PrestigeR&D (Jan 6, 2010)

How's your burner flame.....:blink: normal,...med,...weak......does ithe blower shut off and the burner stay on.....


Just curious....:blink:

So your saying your furnace is not cycling correctly....

Not sure what your situation is.....

I'm not an hvac guy and I am sure Flashheat will be on to try and help....just I have had so many issues with mine that I am becoming familiar with the workings...and it was not an admiration of mine.....


Sucks when they mess up....but it helps to know how it works...sometimes - with all this new technology it's best to get a pro in......

But don't give up....

B,


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## Sparkylu38vb (Nov 27, 2013)

Burners all running good with strong blue flame. Burners and blower shut down induction fan continues to run then unit cycles on again.


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## PrestigeR&D (Jan 6, 2010)

So your getting heat,...just keeps cycling- non stop....:blink:


Can you give some details about the furnace.....:blink: age, some details.....



B,


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## Sparkylu38vb (Nov 27, 2013)

It's an Armstrong Ultra SX 80, guessing age is from the Mid 90's. Honeywell board and honeywell smart valve for the gas. Since it's not short cycling I'm guessing its not the flame sensor guessing it might be high limit switch on the cycling issue. Still perplexed by stat shutting off intermittently since every time I checked voltage at board and stat I have 28.6 volts between C & R. Might exchange stat to see if it's defective.


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## flashheatingand (May 3, 2008)

Smart valve? Oh-Oh. They have an internal control board, within the valve. It's a parts specific situation. Obviously not being there, it's hard to say Perhaps you have a bad control board. But betting the odds, the issue is within the valve itself.


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## Sparkylu38vb (Nov 27, 2013)

Yeah, after roaming around the internet on this, it seems the general consensus is these valves are junk. Any recommendations on a replacement? I know the 24v goes through the valve, would this impact the intermittent problem with losing power to stat?


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## flashheatingand (May 3, 2008)

It's not like smart valves are junk, but they are known to fail. You can't just get a universal valve, going to need to get the oem part. Granted, it's a lot easier for me to spend somebody else's money. But, now might be a good time to replace the furnace altogether. 

Next year it could be the blower motor, the following year, the inducer motor...etc. Before you know it, you would have been better off with new gear. 

I think you are better off getting a hvac guy to look at this. Replacing the smart valve, because some jamoke on-line is hypothizing is not wise. Who knows? It could be a loose connection. We all have mis-diagnosed at some point. It's an empty feeling to spend $150+ on a part, just to see the problem recur. Good luck


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## PrestigeR&D (Jan 6, 2010)

:laughing:........and so on....:laughing:


Thanks for chiming in FH...:thumbsup:



B,


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## B.Scott (Feb 1, 2013)

I'm not familiar with your furnace but what about the high limit switch on the blower control?


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## flashheatingand (May 3, 2008)

Here is one reason not to take internet advice too serious. Its possible the smart valve is giving a trouble code.

Somehow my first reading made me think that things just stopped altogether. Its also possible the valve is giving off a trouble code..


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## PrestigeR&D (Jan 6, 2010)

Not enough info to make an internet guess,,,,:laughing:


But seriously,..and I don't know much about it ,...to me ...not enough info,,,,,,:blink:

Wouldn't you say FH.....:blink:

It's a swag......:blink:



B,


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