First, I’m a bit new at this, but I’m a nuclear engineer and I understand basic electricity. I’ve also successfully done some troubleshooting with my own irrigation system. Basically, I believe you need to figure out whether the red wires are indeed common, and if so, connect them directly via jumper to another C terminal to improve the common connection. Then troubleshoot the bundle 4 wires to determine where the problem is.
Looking at the wiring, I see 4 bundles - if you number them from left to right in the photo, you see that
all four bundles have a red wire connected to a wire nut - this makes it pretty likely that red is common.
Bundle 1 - red to 4 connection wire nut, green to zone 1 valve
I’m thinking that if zone 1 works, then red must be common, and all 4 reds must also be connected to the white wire in bundle 2 somewhere out in the yard
Bundle 2 - red to 4 connection wire nut, white to common, green and blue unused
This bundle connects to no valve, but to white common and red (that seems to be common) - it could be this bundle that connects red and white together somewhere out in the yard
Bundle 3 - red to 4 connection wire nut, green pump motor, white zone 2, green zone 3
SInce you say that zones 1, 2, and 3 work, the white common wire must be common for valves/zones 1, 2, and 3
Bundle 4 - red to 4 connection wire nut, blue zone 4, yellow zone 5, white zone 6, and green zone 7
All four of these don’t work, so it’s logical to conclude the problem is in this bundle of wires, or the problem is in one of the connections out at the 4 valves.
I would disconnect wires and check resistance from white (common from bundle 2) to the bundle of reds. It should be zero if the commons are properly tied together somewhere out there. If it’s a few ohms that’s probably OK, but it shouldn’t be in the tens of ohms. Note that if bundle 3 serves only to remotely connect white and red together, then a shorter path to this is to run a white jumper from the 4 reds wirenut up to another of the C common terminals.
Now check the resistance for zones 4-7 - they should all be in the 20 - 60 ohm range, and since they’re probably the same model of solenoid, they should all be pretty close to each other in reading. If one or more have extremely high resistance, or infinite resistance, then there is a break in that wire that goes to those valve(s). If you can locate the three valves, you can do a couple of things: first, you can confirm that the red wire is indeed common for those three - in other words, at valve 4, the blue wire from the bundle should be connected to one of the black solenoid wires, and the red wire should be connected to the other AND the red wire should also be connected to the red wire in the bundle that runs to the next valve. To figure out whether the whole bundle has been severed, you can temporarily connect the wires going into one of the valve boxes together. It might be that the red wire is severed, and you could repurpose the (beige unused) wire in it’s place. At the very least, out at the valve you can connect two or more wires together temporarily, then see if the resistance back at the controller is zero for those connected together. If that’s the case, then for each pair that reads zero back at the controller, the two wires are intact out to that box.
Sorry for the length of this post, but I was thinking it through as I went. Hope it helps!
So “bundle 1”, the green wire is going to the M port, hard to tell by pic. Bundle 3 goes to zones 1-3 with red common bundled.