I have an 18 K unit with E7 error on heat mode

I just installed a YMGI brand mini-split AC and had exactly the same problem. AC worked fine, but when I tried using heat mode I would get an E7 error.

After talking to their tech support I discovered the problem. There was a separate cable that needed to be connected that I'd forgotten to hook up. This cable runs from the internal unit to the outdoor unit and connects a defrost sensor.

In my case I had totally missed that cable when I installed the unit. After running another line and connecting it the unit is now functioning normally.

If this is a new install, then make sure all your cables have been run. If it was previously working, then check to see if one of the cables had become disconnected. If it's not the cable, then it's probably the sensor.

Good luck

I am having the same E7 issue. All of the wiring is connected correctly except for the indoor wire connector. I have not been able to locate the outdoor probe wire. I had an electrician install this for me and could use a little help figuring out what this wire looks like and where it is to connect with the outdoor unit. If the unit did not come with one, whats my next step in getting my hands on one? Thanks for your help!