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HVAC and Plumbing Distributor
Steven Simmons

Steven Simmons

Technical Services Manager
Southwest District

Furnace Rapid Flash

This article is in reference to non-twinned furnaces. Pictures are shown of a Carrier 58STA110-13122

The manual and stick for CarrierBryant/Payne furnaces show the following:

manual text

At first glance, this seems simple. Just swap the two incoming power wires, right? But the furnace has been running for years at the home with no issues and swapping the wires produces the same rapid flash situation…. What gives?

Let’s tackle how to attack this fault:

FIRST, trace the wires or read the schematic to determine where L1(black) and Neutral(white) land on the board- Pointed in green. Use a voltmeter to Verify the follow:
L1-N= 120vac
L1-Ground=120vac
N-Ground=0vac
This will verify that the ground to the equipment is good and that L1 is the HOT wire and not N. ***If L1 to Ground is 0vac and N to Ground is 120vac then simply reverse the two wires as they wire nut to the furnace power in the Junction Box highlighted in Purple.

connection diagram

Second, Use the Voltmeter to check AC voltage from R (on the screw terminal strip) to L1. This test SHOULD read mid-90’s, my test produced 93.4Vac shown here:
This picture is an actual reading with my meter as well as a layover of the schematic showing the terminals that I am checking.

meter reading

This test will verify that low-voltage R is truly the hot wire. IF this test produces roughly 145 Vac then this means that the transformer low voltage is out of Phase. *** The easiest way to correct this is to swap SEC-1 & SEC-2 on the board. (this is commonly seen when people replace transformers on furnaces)

Third, if the high voltage and low voltages have been checked for proper phasing and they are correct, and the board is still showing a rapid flash, at this point it is recommended to replace the furnace control board.

Lastly, If everything above checks good and the board is changed and the unit produces a rapid flash then you could (temporarily) try wiring the furnace to an extension cord and plugging it into a receptacle within the home. After ensuring the L1 and N are correct once more, if this corrects the rapid flash then the issue is with the breaker feeding the furnace.

There will/can always be a “one in a million” situation but for the vast majority this guide will assist in finding the reason for the furnace rapid flash.

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Alabama Locations

Anniston (256) 241-3026 105 E D St, Anniston, AL 36201
Auburn (334) 734-8011 2295 1st Ave, Opelika, AL 36801
Birmingham (205) 250-7714 516 31st St N, Birmingham, AL 35203
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South Carolina Locations

Hilton Head(843) 689-34043715, 21 Hunter Rd, Hilton Head Island, SC 29926

Florida Locations

Fort Walton Beach(850) 244-201776 Beal Pkwy SW, Fort Walton Beach, FL 32548
Panama City(850) 913-05853012 Lisenby Ave, Panama City, FL 32405
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Mississippi Locations

Hattiesburg(601) 579-96701851 Lincoln Rd, Hattiesburg, MS 39402
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Commercial Sales

Norcross – North Georgia Hub
(800) 282-4911

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(800) 342-9250

Loxley – Gulf Coast Hub
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Savannah – Southeast Hub
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Commercial Parts

 CompanyWeb AddressDescription
Airzonewww.airzoneinc.comCustom and Underfloor Air Handlers
Aladdin Metal Productswww.aladdinmetalproducts.comCurb Adapters and Roof Curbs
Aprilairewww.aprilaire.comIndoor Air Quality Products
Autaniwww.autani.comBuilding Automation and Controls
Bardwww.bardhvac.comHeat Pumps,Gas/Electric, and Wall Mounted Air Conditioners
Bryantwww.bryant.comCommercial, Industrial, Residential Heating & A/C Products and Controls
Carrierwww.commercial.carrier.comCommercial and Residential Heating & A/C Products
Data Airewww.dataaire.comPrecision Air Control for Data Processing Centers
 DXairwww.dxair.comPool dehumidification systems
 First Companywww.firstco.comFan Coil Units
Global Plasma Solutionswww.gpshvac.comAir Purification and Bi-Polar Ionization
 Greewww.greeusa.comPTACs
 Hayes Fluid Controlswww.haysfluidcontrols.comHose Kits and Control Valves
 iAirewww.myiaire.comCommercial Air Purification using ionization with energy savings
 IslandAirewww.islandaire.comPTACs, Vertical Units, Water Source Heat Pumps
 i-Vuwww.commercial.carrier.comBuilding Automation and Controls
 Magic Airewww.magicaire.comFan Coil Units
 Micro Metlwww.micrometl.comRoof Curbs, RTU Accessories, & ERVs
 Modinewww.modine.comGas-Fired Unit Heaters, Duct, Furnaces, Hot Water Cabinet Unit Heaters, Makeup Air, and Dedicated Outdoor Air Systems
 Network Thermostatwww.networkthermostat.comInternet Thermostats, Wifi Themostats, Ethernet Thermostats
Paynewww.payne.comResidential Heating & A/C Products
Rawal Deviceswww.rawal.comContinuous Capacity Modulation and Dehumidification for DX Systems
Renew Airewww.renewaire.comFixed-Plate ERVs
Totalinewww.totaline.comCompressors, Parts, and Supplies
United CoolAirwww.unitedcoolair.comModular All-Indoor HVAC Systems
 Warren Technologywww.warrenhvac.comElectric Heaters
 Wilo Pumpswww.wilo-usa.comPump Systems for HVAC and Water Supply and Sewage