Dometic CCC 2 Error Code E7

We have 3 air conditioners, with the transfer switch that should zone them as either bdrm + front or front + garage. We just took delivery and set up for the first time this week. When I tried to turn the air on, nothing happened - thermostat was blank on all 3. I looked at the circuit breaker and fuses, found a blown fuse. Replaced it, now the bdrm and garage air come on at the same time and the front room doesn't come on at all, no matter the position of the transfer switch. This shouldn't be possible, since those two should be on separate zones, but I guess they wired it so that the bedroom is the main and front or garage can be chosen. I'll have to get that corrected.

The front room thermostat shows an E7 error code, which is "Loss of 120 VAC power to all power mod- ule boards on the system. The system will shut down."

I saw another thread about this, which resolved when the romex wire feeding the transfer switch was checked and found to be damaged.

My question: is there anything else that could be causing this… for example, could I have done something differently when I replaced the blown fuse? I tried to power everything down for a restart, by unplugging the shore power, but then the battery kept everything powered and I was so hot and frustrated that I just plugged the new fuse in.

I have a tech coming out to my site in a few weeks (soonest available), but I would love to know if there is anything I could be trying in the mean time.

Thanks,

Erika

I'd check the wires on the back of the 3-way switch. Carefully. Sorry I have no idea how it's wired, but perhaps there'll be an obvious problem with one of the wires. If you do find something obvious, before working on it, turn off the main breakers coming into the RV, either at the pedestal, or in the circuit breaker box.

Thanks. I will probably at least take the cover plate of the switch and visually inspect. I am very hesitant about doing anything involving electricity, but at least this doesn't involve a ladder! I'll be sure to unplug, turn off the battery AND turn off at the breaker - just in case!