Lennox furnace E113: High line voltage
E113 means the incoming line voltage is above the furnace's nameplate rating. Lennox's action is to bring the supply within range; normal operation resumes five seconds after it recovers.
Applies to: Lennox gas furnaces with a seven-segment diagnostic display on the control board, such as the ML193UHEK, per installation instructions 508565-01.
What it means
Less common than low voltage and less discussed, but harder on electronics. High supply voltage stresses the control board, the motor windings and anything with a capacitor in it, and it shortens component life without producing any obvious symptom until something fails. The furnace measuring this and reporting it is the useful part — a house with chronically high supply voltage will quietly age every appliance in it, and a stored E113 is often the first written evidence anyone has of that.
Most common causes
- A utility supply running high, which affects the whole house.
- A transformer tap set incorrectly on the utility side.
- Light loading on a circuit that normally carries more, raising the measured voltage.
- A wiring fault producing an abnormal reading.
How to diagnose it
- Note whether other electronics in the house have been failing unusually often — that is the pattern high supply voltage produces.
- Note whether the code is constant or intermittent.
- Measurement is technician or electrician work.
- If the whole house is affected, the utility needs to know.
How to fix it
- Provide power voltage within the proper range, which is Lennox's instruction.
- If the supply is genuinely high at the meter, this is a utility matter rather than an HVAC one.
- Normal operation resumes five seconds after the fault recovers.
- Worth acting on even though the furnace keeps running — the damage is cumulative.
Notes
The nameplate on the furnace states the rating this is measured against, so what counts as high is specific to the unit rather than a universal number.
Related
All codes for this manufacturer
Lennox furnace alert codes — every code, with what differs between models.
What counts as high on this furnace
For the ML193UHEK that the cited manual covers, the generator-use section pins down the numbers: the furnace wants 120 volts ±10% — a working window of 108 to 132 volts — at 60 hertz, from a supply with less than 5% total harmonic distortion. That last figure is why E113 so often appears specifically on generator or temporary power. A portable generator running lightly loaded tends to overshoot its voltage, and a cheap one with a rough waveform can push readings out of range even when its meter says 120. If this code shows up only during outages, suspect the generator's regulation before the house wiring.
Where E113 sits in the power-quality family
The seven-segment control dedicates a block of codes to the incoming supply, and it helps to see them together — they are diagnosed by the same person with the same meter:
| Code | Fault | Recovery per 508565-01 |
|---|---|---|
| E110 | Line voltage low | Clears 5 seconds after recovery |
| E111 | Line/neutral reversed | Resumes 5 seconds after rewiring |
| E112 | No ground — shuts down | Resumes 5 seconds after recovery |
| E113 | Line voltage high | Resumes 5 seconds after recovery |
| E114 | Not 60 hertz | Resumes 5 seconds after recovery |
| E115 | 24 V control supply low | Clears after recovery |
A furnace logging several of these together is describing one upstream electrical problem, not five furnace problems.
What the fix costs
There is no furnace part to replace for E113 itself — the money question is what the high voltage is doing while it persists. Expect a diagnostic or service call at $75–150 to confirm the reading, then either a call to the utility (a supply running high at the meter is their equipment and their cost to correct) or an electrician if the problem is inside the house. The bill worth avoiding is the downstream one: chronic overvoltage cooks electronics, and a control board replacement runs $400–900 installed. Acting on a stored E113 is cheaper than ignoring it. More codes like this across brands: power supply codes.
DIY or call a pro
Measuring line voltage means a multimeter across live 120-volt terminals — leave that to a technician or electrician. What a homeowner can do for this specific code costs nothing: note whether the code coincides with generator use, ask neighbors on the same utility transformer whether their lights run bright or appliances have been failing young, and report a suspected high supply to the utility, which will usually check it free. Skip anything involving the furnace cabinet's wiring, and if the code is constant rather than occasional, stop waiting — the damage from sustained overvoltage is cumulative even while the furnace appears to run normally.
What this looks like
From the outside, this usually shows up as the furnace is completely dead — that walkthrough covers what to check in order, and when it stops being a homeowner job.
This can also show up as the furnace not turning on at all — that page is a 5-minute checklist before calling anyone.