Advent Air Air Conditioner: “E5”
warning RV air conditioner error codes
What it means
On the Advent ACTH12 thermostat, E5 indicates a DC supply-voltage problem — the system voltage has dropped too low for reliable operation (the control expects roughly 10 volts or more).
Most likely causes
- Low RV battery / house battery voltage most likely
- Loose or corroded DC power connection to the control common
- Undersized or long DC wiring causing voltage drop less common
Safe checks you can do yourself
- Check the house battery state of charge and confirm the converter/charger is working or the unit is on shore power.
- With power off, inspect the DC power connections at the control for corrosion or looseness.
- Measure the supply voltage at the control if you have a multimeter and confirm it is above about 10 volts.
How to reset / clear E5
- Restore proper DC voltage (charge the battery or connect shore power).
- With the thermostat Off, hold Mode and Fan together, press Power, then release all three buttons to clear the display.
When to call a technician
If battery voltage is healthy and connections are clean but E5 persists, have the DC supply circuit and the thermostat checked by a technician.
Applies to
Advent Air ACTH12 thermostat · Advent Air ducted rooftop AC systems using the ACTH12 / ACRG relay kit
FAQ
What does Advent Air Air Conditioner code "E5" mean?
On the Advent ACTH12 thermostat, E5 indicates a DC supply-voltage problem — the system voltage has dropped too low for reliable operation (the control expects roughly 10 volts or more).
How do I reset Advent Air Air Conditioner E5?
Restore proper DC voltage (charge the battery or connect shore power). With the thermostat Off, hold Mode and Fan together, press Power, then release all three buttons to clear the display.
What is the most common cause of E5 on a Advent Air Air Conditioner?
The most likely cause is low rv battery / house battery voltage.
Related · Advent Air air conditioner
Sources
- Advent ACTH12 Operating Instructions (full text) — ACTH12 error code table: E5 ensure DC voltage is above 10 volts (Internet Archive / Manualzilla)
- Troubleshooting An E5 Error Code On An Advent Air RV Air Conditioner — E5 troubleshooting (low voltage / communication) (etrailer)
Note: Sources conflict on Advent E5: the ACTH12 manual table ties E5 to DC voltage below ~10V, while several etrailer/JustAnswer expert answers describe E5 as a thermostat-to-controller communication fault. Verify against the exact thermostat revision on your unit; the related 'Lo' display also indicates low DC voltage.
● Last verified 2026-06-29 · compiled from manufacturer documentation. Codes can vary by model year — always cross-check your unit’s manual.