Power Supply Issues

The device wouldn’t turn on so I swapped out the AC adapter with one I new worked. The device turned on, but only long enough to connect and run 1 zone for a couple minutes. It then died. I think there is some sort of faulty device in the head unit that is causing it to lose power. Is this an issue than can be fixed like a faulty fuse or is it new head unit time?

The power supply is likely fine, it is possible that something within your setup is shoring out (drawing too much current). There is a self reset fuse within the controller. If a zone or a master valve is faulty, it may be tripping it.
Try unplugging the device for a few minutes. If it turns on again, check to make sure that your wiring is in good shape & try different zones to see if it’s a particular one which causes an issue.

The problem repeats regardless of the zone and no matter how long I wait to plug it back in. I can get every zone to fire once before the thing shuts itself off…. It can only handle one command without cutting off. The original AC adaptor doesn’t work at all and it only powers up with alternate AC plug in I’ve started using.

Since the original power supply is dead, and the new one triggers an overcurrent protection, it’s clear that issue lies with an MOV, which is a surge protector within Rachio controller.
Seems it has done it’s job and protected the controller, unfortunately it seems to be now shorting.
Repair is pretty cheap and easy, in case you (or your friend) are comfortable with a soldering iron.
There were several discussions (link) on the movs, usually this issue occurs when new users try to use original supply overseas.

That might be above my ability level. If I buy a new controller and install it, can I tie it back in to the app he already has on his phone? I don’t want to have to reset all the zones and set it up from scratch if I don’t need to.

Yes, you can transfer the old settings on the new controller. When you get the new one set up, log in with his information, and it will ask if you want to transfer settings from the old controller.