Amana AMVM970803BN Error Code E18: Supply Air Temperature Sensor Shorted (External)
What Does Code E18 Mean?
Code E18 on the Amana AMVM970803BN means the external supply air temperature sensor circuit is shorted. The temperature reading from this sensor will not appear in the CoolCloud HVAC App, but the furnace itself continues to operate and heat your home — this is a monitoring fault, not a shutdown.
The AMVM970803BN uses these temperature sensors to feed the CoolCloud app comfort and diagnostic features rather than to run basic heating. A short usually comes from damaged sensor terminals or conductors, or a shorted PCB connector — if E18 appears even with the probe unplugged, the fault is on the board side. Heating continues regardless.
This code belongs to the temperature-sensor family on this board: E15/E16 are the external return-air sensor (open/short), E17/E18 are the external supply-air sensor (open/short), and E19/E1A are the onboard return-air sensor (unplugged/short). They are grouped together because each simply removes one temperature reading from the app while heating continues.
What You'll Notice
- The furnace heats normally but the supply-air value is missing or wrong in the CoolCloud app
- The display shows E18
- The fault may follow recent work near the sensor wiring
- No effect on actual heat output
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 → |
How This Is Diagnosed
A technician inspects the supply-air sensor terminals and conductors for a short, and checks whether E18 persists with the probe unplugged, which would place the short at the PCB connector rather than the probe.
Since this is a monitoring sensor, the furnace runs normally while the short is located and corrected.
When to Call a Professional
This code involves components that are not homeowner-serviceable, so have a licensed HVAC technician diagnose and repair it. Keep in mind:
- The supply-air reading remains missing or incorrect in the CoolCloud app
- E18 persists after a power cycle
- You want full CoolCloud diagnostics restored
Frequently Asked Questions
Is E18 dangerous?
No. It is a low-severity fault affecting only the supply-air reading in the CoolCloud app. The furnace continues heating normally.
Why does the app show no supply-air temperature?
The shorted supply-air sensor circuit prevents a valid reading. A technician traces the short in the probe or PCB connector to restore the data.
✓ Verified against manufacturer service manual — March 2026