Amana AMVM970803BN Error Code E18: Supply Air Temperature Sensor Shorted (External)
What Does Code E18 Mean?
Error code E18 on the Amana AMVM970803BN indicates the external supply air temperature sensor circuit has a short. The control board detects near-zero resistance on the sensor input, which prevents a valid temperature reading. The supply air temperature will not be visible in the CoolCloud HVAC App, but the furnace should continue operating.
A shorted sensor circuit means the sensor probe's conductors are making unintended contact with each other or with ground, causing the measured resistance to collapse. This typically occurs where wire insulation is damaged from pinching or abrasion, at connectors where terminal pins have shifted together, or where moisture has bridged the sensor terminals. If the error is reported when the probe is not plugged in, the short is on the PCB connector itself.
A technician should inspect the sensor probe terminals and conductors along their entire length for signs of damage, pinching, or contact with metal surfaces. The PCB connector should be inspected for shorted pins, particularly if E18 appears without the probe connected. A short found in the wiring can sometimes be repaired, but if the PCB connector is the source, the PCB may need replacement.
Common Causes
| Cause | Likelihood | DIY? |
|---|---|---|
| Electrical short in sensor probe terminals or conductors | Most common | ✗ Call a pro → |
| Shorted PCB connector | Common | ✗ Call a pro → |
| Faulty PCB | Uncommon | ✗ Call a pro → |
When to Call a Professional
Contact a licensed HVAC technician if:
- E18 displays — a technician must trace the supply air sensor wiring for shorts and inspect the probe terminals
- If E18 appears without the sensor probe connected, the PCB connector is shorted and PCB replacement may be required
- Chafed or damaged sensor wiring requires professional inspection and repair
✓ Verified against manufacturer service manual — March 2026