Troubleshooting An E5 Error On A Dometic AC system With An Advent Replacement Rooftop Unit

Updated 03/19/2024 | Published 03/18/2024

Question:

We replaced the factory Dometic unit with this unit mainly as preventative maintenance, as the 12 year old factory unit was quite rusted and specifically the accumulator looked as though it may rust through at any moment. The factory unit was working though. We went on a weekend trip this weekend and when we went to turn the A/C on all we got was the thermostat flashing an E5 code. It would do this no matter what setting we tried A/C, Furnace, or Fan I pulled the cover on the A/C unit and checked all the wiring connections and the same at the thermostat and I could see nothing out of line. Is there something more that I can check?

asked by: Ben M

Expert Reply:

Hi Ben,

Without knowing the model number to confirm it's hard to say exactly what that E5 error code means. From what I can see it's either a low voltage warning, a communication error between the thermostat and controller, or an issue with the freeze sensor. You can start by checking the voltage going to the controller and then to the # ACDOM150.

From there you can check the communication wire that connects the thermostat to the controller. I've seen other say that unplugging it from both sides for a few minutes and then resetting the thermostat will help clear the error.

If this doesn't work then you'll need to find the freeze sensor that should plugged into the controller and sitting in the coils of the # ACDOM150 to sense if they start to freeze. Unplug and let the sensor sit for a bit and then reconnect it to the controller and position it back with the coils.

expert reply by: Kevin C