Atwood AFSD12 - User Manual

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Effective 1/15

Part Number 30620

Table of Contents

Questions and Answers

M
Michael VaughnAug 18, 2025
What to do if Atwood AFSD12 Furnace burner fails to ignite and blower fails to run?
- S
  Scott RojasAug 18, 2025
  If the Atwood furnace burner fails to ignite and the blower doesn't run, start by checking the electrical power to the furnace, reconnecting or replacing the power source if necessary. If the power source is ok, replace the thermostat if it’s defective. Also, replace any broken or shorted thermostat wires. Reset the circuit breaker if a current overload protector device has tripped, and check the amp draw from the motor. Finally, inspect the circuit breaker for defects or tripping, referring to the furnace specifications.
A
Amanda NorrisAug 21, 2025
Why Atwood AFSD12 blower does not run?
- R
  Robert ClarkAug 22, 2025
  If the Atwood furnace blower does not run, check the following: * Ensure the temperature selector is correctly set. * Repair or replace any broken or disconnected thermostat wires. * If the heat anticipator is burned out due to a short, repair the short and replace the thermostat. * Replace the relay and thermostat if the faulty relay draws more than 1 amp. * Replace the thermostat if there is no continuity through it with contacts closed and the switch on. * If there is continuity through the thermostat with contacts closed and the switch on, check and reestablish power to the thermostat, reset any tripped circuit breakers, correct poor grounding, correct any loose wires, and replace any defective relays or motors.
P
Philip HinesAug 25, 2025
How to fix soot caused by lazy yellow flame in Atwood AFSD12 Furnace?
- K
  Kathleen IngramAug 26, 2025
  Soot, indicated by a lazy yellow flame in your Atwood furnace, can stem from several issues. Begin by ensuring the gas pressure is at least 11” W.C. with all appliances running, replacing the regulator if necessary. Also, verify that the power supply provides correct voltage. Replace any gaskets with air leaks. Check the combustion wheel installation (it shouldn't be installed backwards or loose), reposition and tighten it if necessary. Inspect for any blockages in the heating chamber or burner head, cleaning or replacing parts as needed. If the motor is faulty, replace it. Finally, ensure the vent kit or draft cap is correct for your unit, replacing it if it is not.
K
Kelly CastilloAug 28, 2025
Why Atwood AFSD12 Furnace does not cycle properly?
- Y
  Yesenia JonesAug 28, 2025
  If the Atwood furnace isn't cycling properly, consider these points. If it cycles too quickly, move the anticipator to a higher amp setting to lengthen the cycle, also ensure the thermostat isn't too close to a heat duct; if it is, relocate either the thermostat or the duct outlet. For high temperature variance, move the anticipator to a lower setting to shorten the cycle.
Z
zacharysanfordAug 31, 2025
Why Atwood AFSD12 Furnace fan runs continuously with thermostat off?
- E
  Evelyn ThompsonAug 31, 2025
  If the Atwood furnace fan runs continuously even with the thermostat set to “off”, there are a few potential causes. The thermostat itself may be defective and need replacement. Alternatively, there could be shorted thermostat leads, which would require replacing the wire or wires. Lastly, a defective relay could be the culprit, necessitating its replacement.
A
Albert AdamsSep 3, 2025
What to do if Atwood AFSD12 Furnace burner ignites then locks out?
- J
  James WillisSep 3, 2025
  If the Atwood furnace burner ignites but the ignition system locks out and turns the burner off, consider the following: * Ensure gas pressure is at a minimum of 11” W.C. with all appliances running, replacing the regulator if needed. * Check for and clear any exhaust blockages. * Reposition and tighten the combustion air wheel if it is loose. * Adjust the electrodes according to furnace specifications, or replace them if defective. * Clean the plug contacts on the circuit board, and replace the board if it remains defective. * Replace the flame sensor wire if it is defective. * Replace any gaskets with air leaks. * Consider replacing the heat exchanger if it is defective.
K
Kimberly VillaSep 7, 2025
Why Atwood AFSD12 Furnace has insufficient heat?
- M
  Miss Jennifer Coleman PhDSep 7, 2025
  If your Atwood furnace isn't producing enough heat, first ensure it's not underfired. Set the gas pressure to 11” W.C. with all appliances running, and replace the regulator if this pressure isn't obtainable. Also, check the main burner orifice to ensure it meets the furnace's specifications. Secondly, inspect the ducting and return air setup, ensuring they meet the furnace's specifications. If the furnace is improperly sized for the coach or conditions, replace it with one of the proper size.
T
Todd HolmesSep 12, 2025
Why Atwood AFSD12 Furnace blower vibrates or is noisy?
- M
  Mark MartinSep 12, 2025
  If the Atwood furnace blower vibrates or is noisy, check if the motor mount is loose and tighten the mounting bracket. Ensure the ducting meets the furnace’s minimum requirements, without excess ducting or unnecessary bends. All closeable registers must be fully open and unrestricted. If the blower wheel is damaged, replace it. If the motor shaft is damaged, replace the motor.
J
Jason SchmittNov 13, 2025
What to do if the blower runs but the Atwood AFSD12 fails to ignite?
- T
  Timothy SmithNov 14, 2025
  If the blower runs but the Atwood furnace fails to ignite, several factors could be at play. First, ensure the power supply is correct. Second, verify that the gas pressure is at least 11” W.C. with all appliances running; if not, replace the regulator. Check that the furnace grounding wires are secure and the air intake is not restricted. Other potential issues include a slow-running motor (check voltage, replace if necessary), reversed 12-volt polarity, a blocked exhaust, a loose combustion air wheel, or a defective/disconnected sail or limit switch. Also, inspect for dirty edge connectors or circuit boards, a defective circuit board or gas valve, a blocked main burner orifice, a defective high tension lead wire or electrode (misadjusted or defective), or an obstructed burner head. Addre...

Summary

Furnace Model Series Identification

AFS Series Model Identification

Nomenclature and specifications for AFS furnaces.

AFM Series Model Identification

Nomenclature and specifications for AFM furnaces.

AFL Series Model Identification

Nomenclature and specifications for AFL furnaces.

79;80 Series Model Identification

Nomenclature and specifications for 79/80 series furnaces.

8500 Series Model Identification

8900 Series Model Identification

85;89 2-Stage Series Identification

Furnace Wiring Diagrams

AFS Series Wiring Diagrams

Wiring diagram for AFS furnaces.

AFM Series Wiring Diagrams

Wiring diagram for AFM furnaces.

AFL Series Wiring Diagrams

Wiring diagram for AFL furnaces.

8500 Series Wiring Diagrams

Wiring diagrams for 8500 series furnaces.

8900 Series Wiring Diagrams

Wiring diagrams for 8900 series furnaces.

2-Stage Furnace Wiring Diagrams

Wiring diagrams for 2-stage furnaces.

Thermostats and Wiring

Bi Metal Thermostat HFH 2000

Digital Thermostat Model 1 H2 C

Thermostat Wiring Requirements

Wiring specifications for Atwood thermostats.

Digital Thermostat Model 2 H2 C Two Stage

Furnace Sequence of Operation

DC Models (Standard Units) Operation

DC Models (2-Stage) Operation

Pilot Models Operation

AC Models Operation

Installation, Maintenance, and Safety

Critical Installation Criteria

Essential rules and precautions for furnace installation.

Annual Preventative Maintenance Inspection

Furnace Components and Terminology

Circuit Breaker, Motor, and Boards

Burner, Electrode, and Assembly

Troubleshooting Guides

Mechanical Thermostat Troubleshooting

Electronic Ignition Models Troubleshooting

Service Parts Lists

Summary

Furnace Model Series Identification

AFS Series Model Identification

Nomenclature and specifications for AFS furnaces.

AFM Series Model Identification

Nomenclature and specifications for AFM furnaces.

AFL Series Model Identification

Nomenclature and specifications for AFL furnaces.

79;80 Series Model Identification

Nomenclature and specifications for 79/80 series furnaces.

8500 Series Model Identification

8900 Series Model Identification

85;89 2-Stage Series Identification

Furnace Wiring Diagrams

AFS Series Wiring Diagrams

Wiring diagram for AFS furnaces.

AFM Series Wiring Diagrams

Wiring diagram for AFM furnaces.

AFL Series Wiring Diagrams

Wiring diagram for AFL furnaces.

8500 Series Wiring Diagrams

Wiring diagrams for 8500 series furnaces.

8900 Series Wiring Diagrams

Wiring diagrams for 8900 series furnaces.

2-Stage Furnace Wiring Diagrams

Wiring diagrams for 2-stage furnaces.

Thermostats and Wiring

Bi Metal Thermostat HFH 2000

Digital Thermostat Model 1 H2 C

Thermostat Wiring Requirements

Wiring specifications for Atwood thermostats.

Digital Thermostat Model 2 H2 C Two Stage

Furnace Sequence of Operation

DC Models (Standard Units) Operation

DC Models (2-Stage) Operation

Pilot Models Operation

AC Models Operation

Installation, Maintenance, and Safety

Critical Installation Criteria

Essential rules and precautions for furnace installation.

Annual Preventative Maintenance Inspection

Furnace Components and Terminology

Circuit Breaker, Motor, and Boards

Burner, Electrode, and Assembly

Troubleshooting Guides

Mechanical Thermostat Troubleshooting

Electronic Ignition Models Troubleshooting

Service Parts Lists

Atwood AFSD12 Specifications

General

Brand	Atwood
Model	AFSD12
Category	Furnace
Language	English

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