Goodman Furnace Fan Speed Dip Switch Settings and Troubleshooting

The Goodman Furnace Fan Speed Dip Switch controls blower motor speeds to balance airflow, comfort, and efficiency. This article explains how dip switches work, where to find them on common Goodman models, recommended settings, step-by-step adjustment procedures, and troubleshooting tips to identify and resolve fan speed problems.

Topic	Quick Reference
Location	Control board inside furnace access panel near blower
Function	Selects blower RPM for heat, cool, and constant fan modes
Common Settings	High/Medium/Low or specific CFM/RPM options per model
Safety	Power off before changing switches; follow manufacturer specs

How Fan Speed Dip Switches Work

Dip switches are small removable toggles on the furnace control board that set discrete electrical paths to control the blower motor speed. Goodman furnaces often use multi-position switches to select speeds for heat, cool, and continuous fan operation.

The blower motor responds to selected wiring taps or electronic speed settings to change RPM and cubic feet per minute (CFM). Correct settings ensure proper heat transfer, efficient cooling, and reduced noise.

Locating Dip Switches On Goodman Furnace Models

Dip switches are usually found on the furnace control board behind the front access panel. On Goodman units, common locations include inside the blower compartment or adjacent to the transformer and terminal strip.

Models with ECM (electronic commutated motors) may use an integrated control module with small dip switches or a multi-position selector. Older PSC (permanent split capacitor) motors often use manual motor tap wires instead of dip switches.

Identifying Control Types: PSC Vs. ECM

Understanding motor type helps determine whether dip switches or tap wires are used. PSC motors typically use colored wires for high/med/low taps. ECM motors commonly use dip switches for precise speed programming and can offer more speed options and better efficiency.

Always consult the furnace model’s wiring diagram or Goodman installation manual to confirm the control type and allowable settings before making adjustments.

Common Fan Speed Settings And What They Mean

Setting	Use Case	Effect
High	Cooling and maximum airflow	Max CFM; improves cooling but may increase noise
Medium	Normal heating or balanced airflow	Balanced comfort and efficiency
Low	Quiet operation or low-heat demand	Lower CFM; reduces noise but may limit heat transfer
Continuous/On	Circulation for air cleaning or pressure balance	Fan runs continuously at a set speed; higher energy use

Some Goodman ECM controllers provide numeric speed selections that correspond to specific RPMs or CFM. If the manual lists CFM values next to switch positions, use those to match desired airflow for system size and ductwork.

Preparing To Change Dip Switch Settings

Prioritize safety by turning off all power to the furnace at the service disconnect and circuit breaker. Verify power is off using a non-contact voltage tester at the furnace control board terminals.

Gather tools: flashlight, small flathead or jeweler’s screwdriver to toggle switches, the furnace wiring diagram or manual, and a notebook to record original settings before changing anything.

Step-By-Step: Adjusting Goodman Furnace Fan Speed Dip Switch

1. Turn Off Power: Shut off furnace power at breaker and service switch.
2. Open Access Panel: Remove the front panel to access the control board and blower compartment.
3. Locate Dip Switches: Identify the dip switch bank or labeled speed selector on the control board per the wiring diagram.
4. Record Current Position: Photograph or note the original switch positions and any wire color tap locations.
5. Change Setting: Use a small screwdriver to toggle the switch gently to the desired position indicated for heat, cool, or constant fan.
6. Secure Panel And Restore Power: Replace access panel, turn on power, and allow the furnace to complete any self-tests.
7. Test Operation: Run system in heat and cool modes and verify blower speeds and comfort. Listen for unusual noises and check airflow at vents.

If the furnace uses motor tap wires instead of dip switches, adjustments require moving the blower motor wire to a different colored terminal on the motor resistor or wire harness. This should be done only when power is off.

Troubleshooting Fan Speed Problems

If the blower runs at the wrong speed, check these common causes: incorrect dip switch positions, a stuck relay, a failing motor, faulty ECM control, or incorrect thermostat fan settings.

Use a systematic approach: verify dip switch positions match the wiring diagram, confirm thermostat fan settings (auto vs. on), check for error codes on the control board LED, and inspect for damaged wiring or connectors.

Symptom: Fan Runs Too Fast Or Too Loud

Possible causes include dip switch set to a higher speed for the current mode or motor taps wired to the high-speed lead. Adjust dip switches to a lower setting for the affected mode. If noise persists, inspect blower wheel balance and motor bearings.

Symptom: Fan Runs Too Slow Or Weak Airflow

Check for dip switches set to low speed, clogged air filter, closed or blocked ducts, or a failing motor. Confirm motor RPMs if possible, and ensure the correct wire tap or dip position is selected for the desired CFM.

Symptom: Fan Does Not Run At All

Verify power to the furnace, thermostat calling for heat/cool, and fuses or board-level breakers. If dip switches are correct and power is present, the issue may be a defective relay, capacitor, or motor requiring professional diagnosis.

When Dip Switch Changes Cause Operational Issues

If changing dip switches triggers error codes or the furnace locks out, power-cycle the unit and revert to the recorded original settings. Consult the furnace error code chart found on the access panel or in the manual to interpret LED blink sequences.

Some Goodman control boards run self-checks on startup and may require a short delay for new settings to register. If problems persist after reverting settings, contact a certified HVAC technician.

Safety And Warranty Considerations

Modifying dip switches is generally within homeowner capabilities for simple speed selection, but improper changes can lead to inadequate heating, cooling, or motor stress. Always follow Goodman installation and service manuals.

Unauthorized modifications or damage caused by incorrect adjustments could affect warranty coverage. Keep records of any changes and consult warranty terms or a licensed contractor before making significant alterations.

Efficiency Tips Related To Fan Speed

• Match Fan Speed To Mode: Use higher speeds for cooling and moderate speeds for heating to optimize heat exchange and comfort.
• Use Thermostat Fan Auto: Running the fan continuously increases energy use; set thermostat fan to Auto for efficiency unless constant circulation is needed.
• Check Filters And Ducts: Restricted airflow forces the blower to work harder; replace filters regularly and ensure ducts are unobstructed.
• Consider ECM Upgrade: ECM motors with programmable dip switches deliver better efficiency and variable speeds than older PSC motors.

Maintenance Checklist For Reliable Fan Operation

• Inspect and Replace Air Filters Every 1–3 Months.
• Clean Blower Wheel Annually To Prevent Imbalance.
• Lubricate Motor Bearings If Applicable (Some Motors Are Sealed).
• Verify Dip Switch Positions During Annual Service And Record Settings.
• Check For Wire Corrosion Or Loose Connectors At The Control Board.

Frequently Asked Questions

Can Changing Dip Switches Damage The Furnace?

If done correctly and within manufacturer-specified options, changing dip switches will not damage the furnace. Incorrect settings that create improper airflow or overload conditions can stress components over time.

How To Know Which Switch Controls Heat Vs. Cool Fan Speed?

The wiring diagram on the inside of the furnace panel or the installation manual labels switch functions. Switch groups are commonly labeled “H” for heat, “C” for cool, or “ON” for continuous fan.

Are Dip Switch Settings The Same Across All Goodman Models?

No. Settings and switch positions vary by model and by motor type. Always refer to the specific model’s manual to identify valid positions and their corresponding RPM or CFM values.

Is It Better To Change Motor Tap Wires Or Use Dip Switches?

ECM motors with dip switches offer finer control and improved efficiency. Changing motor tap wires is common on PSC motors but provides fewer discrete speed options and is less precise.

When To Call A Professional

Contact an HVAC technician when diagnostics involve electrical components, motor replacement, control board faults, or when warranty coverage may be affected. Professionals can measure CFM, confirm motor health, and program ECM parameters safely.

A certified technician should be called if the furnace displays persistent fault codes, the blower hums without spinning, or adjustments create intermittent operation or safety lockouts.

Additional Resources

Goodman installation and service manuals, wiring diagrams on furnace access panels, and official technical bulletins provide authoritative guidance on dip switch layouts, speed charts, and error code interpretation.

Local HVAC forums and manufacturer-authorized service centers can provide model-specific advice and hands-on support for complex issues requiring field testing or parts replacement.