Temperature sensor
Common error-code part. Confirm resistance and connector style.
Goodman Heat Pump E1 Error Code — What It Means
On Goodman heat pump systems, error code E1 typically indicates a high-pressure or low-pressure switch fault — a refrigerant system safety switch has opened and shut down the compressor. The E1 code appears on some Goodman heat pump model displays and on the air handler control board’s diagnostic LED (as 1 flash in certain configurations). Exact meaning varies by model year and control board revision.
Common Causes
- High-pressure switch trip (cooling mode) — In cooling mode, the high-pressure switch opens when refrigerant pressure on the high side is too high. Most common cause: dirty outdoor condenser coil, outdoor fan not running, or refrigerant overcharge.
- Low-pressure switch trip (heating or cooling) — Low-side pressure dropped below the minimum. Causes: low refrigerant charge (leak), expansion valve problem, or dirty indoor coil reducing airflow.
- Failed pressure switch — Pressure switches have a mechanical membrane that can fail in the open position, causing nuisance trips even when system pressures are normal.
- Loss of refrigerant — A refrigerant leak causes chronically low suction pressure, tripping the low-pressure switch repeatedly.
Step-by-Step Fix
- Reset the system — power off the heat pump at the disconnect, wait 30 seconds, and restore power. Allow the system to restart. If E1 returns within 5 minutes of startup, the fault is active rather than a nuisance trip.
- Check the outdoor coil (cooling mode) — if the fault appears in cooling, inspect the outdoor unit. A coil caked with cottonwood, leaves, or dirt will cause high-pressure faults. Clean with a gentle coil cleaner and rinse from inside out.
- Check outdoor fan operation — verify the outdoor fan starts when the compressor runs. A failed fan capacitor (often 5–7.5 µF) causes the fan to hum but not spin, leading to rapid high-pressure buildup.
- Check indoor filter and coil — for low-pressure faults, a clogged evaporator coil (ice buildup from a dirty filter) is a common cause. Replace the filter and allow the coil to thaw before restarting.
- Test the pressure switches — with the system off, disconnect one wire from each pressure switch and test with a multimeter. A normal (closed) switch should show continuity at rest. If a switch is open at rest with normal system pressures, the switch has failed.
- Check refrigerant charge — if the low-pressure switch trips repeatedly on a clean coil with good airflow, refrigerant charge is likely low. A certified HVAC technician needs to check pressures and add refrigerant.
Parts Often Needed
| Part | Notes |
|---|---|
| High-pressure switch | Typically 400–450 PSI cutout for R-410A |
| Low-pressure switch | Typically 40–50 PSI cutout for R-410A |
| Outdoor fan capacitor | 5 µF or 7.5 µF / 370V (check existing cap label) |
Technician Tips
Goodman furnaces use a simple LED flash system on the control board. The diagnostic LED is usually visible through the blower compartment window. Count the flashes between pauses — that’s your error code. One flash = normal operation. Two flashes = pressure switch fault. Three flashes = limit switch. Four flashes = flame sensor. Goodman flame sensors are notorious for carbon buildup — cleaning with emery cloth every 2-3 years prevents most lockout calls. The control board on GMS8 and GMSS9 models is particularly sensitive to voltage fluctuations — if you see multiple different codes, check the transformer output (should be 24VAC ±10%).
Prevention: Install a whole-house surge protector on the furnace circuit to prevent board damage from power spikes.
Need Replacement Parts?
Before ordering, match the furnace part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.
When to Call a Pro
If E1 returns after a reset and the outdoor coil is clean, have a certified HVAC tech check refrigerant pressures. A low charge means there’s a leak — adding refrigerant without finding the leak is a waste of money and harms the environment.