Testing M with voltmeter

post by greenhut on Jun 30, 2023

My Rachio has been working well for a while. Setup with 2xMunro pump relays for lake water.

Rachio connected to wifi and appears to be fine from the App.

Noticed sprinklers weren’t running, and pump solenoids weren’t clicking “on” when Rachio activated a zone.

Seems like the Rachio might not be energizing the M connection properly (it is setup properly in the software for a pump relay).

Connected the M wire running to the relays to the C connection and both relays activated properly.

How do I test this with a multimeter? I do see 24v AC between M and C, but this is even with no zones on.

thanks!

post by Thomas_Lerman on Jun 30, 2023

Can you post any pictures and or tell us which wires for the pump relay are going to which terminals on the Rachio?

post by greenhut on Jun 30, 2023

Pics tomorrow, but pretty simple - the M connection goes to the positive of the pump relays. Again, this configuration has been working perfectly for at least a year - no wiring changes.

It’s almost like the Rachio has partially failed in its ability to properly control its ports.

post by Thomas_Lerman on Jun 30, 2023

You should have a wire to go to “C”

post by greenhut on Jul 1, 2023

Thanks for working through it with me Thomas. I do have wires going to a couple of the C terminals. I assume these only go out to the valves, but one might make its way to the relays. Is this common any different in practice from another house neutral? Im wondering if I may have wired a “common” from a source other than the Rachio to the relays. If so, its possible it was disconnected when some other recent electrical maintenance was done…

Still - not sure why I see 24V between Rachio C and M when Rachio isn’t running any zones?

post by Thomas_Lerman on Jul 1, 2023

I do not know what would happen if you connected the “C” to just any common. It might work, but seems like it could be dangerous. I would be wrong though.

I presume that you configured that terminal, through the app, to be a pump?