Heating, Air Conditioning, Fridge, HVAC/armstrong ultra v tech 91


led light on furnace blinking 3 times,do not have manual,furnace not maintaining temp in home

I believe the 3 flashes is for the pressure switch. Check to see if there is a wiring diagram glued inside the unit.  You might find a list of codes on it.

The pressure switch could be closed before the inducer fan is on.
You could have an issue with the inducer fan, the flue, or heat exchanger etc....
The switch could be faulty.


Heating, Air Conditioning, Fridge, HVAC

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Craig HVAC Expert


I have been in the HVAC field for the past 18 years. I can help with most HVAC questions. I work on commerical buildings for the most part, and have yet to find anything I could not troubleshoot and repair, when repairable. I work on small 1 ton units to a 2500 ton chiller. Troubleshoot air flow, elect, and control problems. I attend regular classes to keep up with the latest and greatest.


I work on commerical sites, hospitals, gov't buildings. I can troubleshoot just about anything in the HVAC business.

5 years trade school, VFD training classes, Liebert factory training, some York and Trane factory training.

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