Lennox Furnace Code E113: High Line Voltage Fixes & Costs

Last updated Sep 22, 2026 · By fixme.vip Editorial

Lennox furnace code E113: what it means

Code E113 on a Lennox furnace means the unit control has detected high line voltage — the incoming 115/120VAC power supply is measuring above the acceptable range the control is designed to run on.

The control watches its supply voltage as a self-protection feature. When voltage climbs too high, the furnace holds operation rather than risk damaging the control board, blower motor, inducer, transformer and other electronics that are sensitive to overvoltage.

Which systems show “E113.” Alphanumeric alert codes like E113 are displayed by Lennox communicating (iComfort-enabled) furnaces — the unit controller and the matching communicating thermostat report them as E-codes. If your furnace is an older, non-communicating model, the control board signals faults with LED flash patterns rather than E-numbers, so a supply-voltage problem on that equipment will show up as a flash code (or simply as a furnace that won’t start) — not as “E113.” Read the diagnostic legend printed inside the blower door or on the control to translate what your specific unit is showing.

This is a supply-side / electrical code. It is not caused by ignition, flame-sensing or gas-supply problems. Lennox uses separate codes for low line voltage, polarity/grounding, and ignition faults — check your unit’s legend to identify those. E113 is specifically about the quality of the power reaching the furnace.

Auto-reset behavior is not consistent across Lennox controls. Some controls will drop the code once voltage returns to range; others hold until power is cycled. Don’t assume either behavior — the diagnostic legend for your unit governs, and exact voltage thresholds differ between controls as well.

Lennox furnace code E113: common causes, ranked by probability

1. Utility overvoltage — the power company is delivering voltage above nominal (a sustained high reading at the meter). This is the most common genuine cause and is outside your home.
2. Neutral or service problems at the panel — a loose, corroded or failing neutral connection can cause voltage on one leg to swing high. This is a serious electrical fault requiring an electrician.
3. Recent electrical work or panel changes — miswiring after service upgrades, generator/transfer-switch installs, or solar interconnections can push furnace voltage out of range.
4. Board sensing fault — the control itself misreads voltage. A technician confirms this by comparing the control’s reading against an actual meter measurement. A code that is on constantly while no other appliance or light in the house misbehaves most often points here rather than to the supply, because a real sustained overvoltage usually causes symptoms elsewhere in the home.
5. Transient spikes near measurement — nearby large loads cycling off, or storm-related surges, can momentarily register high voltage and set the code. This fits an intermittent code better than a constant one.

How to fix Lennox furnace code E113: safe checks first

These are the only steps a homeowner should do:

• Check the thermostat — confirm it’s set to Heat and the target temperature is above room temperature, so you know the furnace is actually being called.
• Replace thermostat batteries if it uses them and the display is weak or blank.
• Reset the breaker once — switch the furnace breaker fully off, wait 30 seconds, then back on. Do this only one time.
• If E113 returns after that single reset, leave the furnace off — turn the furnace switch (or breaker) off and call an HVAC technician. Don’t keep running the unit while the code is active, and don’t reset it again.
• Check the furnace switch — the wall switch that looks like a light switch near the furnace should be On when you’re testing.
• Look for signs of a wider problem — lights dimming/brightening, other appliances misbehaving, or a recent utility notice. These point to a supply issue you should report to your utility.
• Note whether the code clears or returns — this helps the technician a great deal.

Do not open the furnace cabinet, test voltage yourself, or repeatedly reset the unit. High-voltage electrical work is not a DIY job.

How a technician will diagnose it

A qualified technician or electrician will typically:

• Measure incoming line voltage at the furnace with a multimeter and compare it to the acceptable range for your control.
• Compare readings at the furnace, the panel, and the meter to locate where the high voltage originates.
• Verify the control’s own voltage reading against the meter to rule out a faulty sensing circuit.
• Inspect the neutral and service connections at the panel for looseness or corrosion, which can drive voltage high on one leg.
• Review any recent electrical work, generator/transfer switches, or solar systems that could affect the supply.
• Refer to the utility or a licensed electrician if the overvoltage is confirmed to be coming from the service rather than the furnace.

If they find the voltage is genuinely in range but the code persists, they’ll investigate the control board.

Symptom, cause and what to do

Lennox furnace code E113 repair cost

Honest US ranges — your situation may differ:

• Diagnostic / service call: $90–$200
• Breaker reset / no fault found: $0 (DIY) or covered in the service-call fee
• Panel neutral repair (electrician): $250–$900 depending on severity; work on the service-entrance conductors themselves may be the utility’s responsibility rather than a billable electrician job, so confirm who owns the failing section before authorizing work
• Utility service correction: typically $0 to the homeowner (utility responsibility) once reported
• Control board replacement (if sensing fault confirmed): $400–$800 installed
• Whole-house surge protector (recommended after overvoltage events): $200–$500 installed by an electrician

Overvoltage caused by the utility is usually corrected at no charge to you, but confirm the source before authorizing internal repairs.

Related codes

Lennox uses separate alert codes for other electrical and ignition-side conditions — including low line voltage, polarity and grounding problems, and ignition or flame-sensing faults. The numbering differs between communicating controls and flash-code boards, so check the diagnostic legend printed on your unit (inside the blower door or on the control) or the literature for your specific model rather than assuming a neighboring number means a related fault.