Checking if rain sensor is connected to common wire and working?

Recently installed a Rachio 2nd generation to replace my Rain Bird ESP-6TM controller. My home has a rain sensor outside attached near the roof, but the old controller didn’t have any connectors for a rain sensor, and the cable coming out of the wall going to the old controller also only had 4 wires which were connected to “COM”, and 1,2 & 3 so I’m assuming these are common and 3 zones.

I’ve got these connected to the same connections on the Rachio controller, and everything appears to be working fine with starting the sprinklers in each zone (tested using the manual start, haven’t tried the scheduled jobs yet).

There were also 3 wires connected from the power adapter from the wall power outlet to the old controller, which do not appear to have anything to do with the rain sensor, and I think they can be safely ignored.

The cable from the rain sensor outside drops into a PVC pipe which runs down the outside of the house and into the ground, so I’m not sure exactly where it leads to. However, I’m assuming that as the old controller did not have connectors for a rain sensor, it’s using the alternative way of wiring where it hooks into using the common wire instead.

We had a short thunderstorm today and while it was pouring down, I tried to manually start the sprinklers in zone 1 for a couple of minutes using the Rachio app to test the rain sensor and they began running immediately for the 2 minute duration before turning off.

Does this mean that the rain sensor is not connected / not working? I would’ve thought that if my assumption is correct about this being hard wired into the common connector is correct, then when the rain sensor is tripped, even a manual start of the zones should not work?

Well, I won’t be too much help, sorry :frowning: BUT, most rain sensors,have a threshold, meaning they have to accumulate a configured amount of rain before they trip.

So the fact that things worked while it was raining is not really a major concern. Also, if it is a really old rain sensor, it might need to have a few parts replaced. I had an old hunter that used cardboard disks to,slowly absorb water (simulate pr) but they wore out (rotted), so it no longer worked very well ( meaning it did not trip at 1/8 inch of rain accumulation) iso i replaced it with a wr2 as I could no longer find the disks I needed.

Yep, that’s a valid point. Done some more reading up, and think there might be a button on top of the rain sensor to cause it to trip, so I’ll take a look at mine later in the week to see if I can use that for testing. Might be better to just replace the whole thing though as it’s over 10 years old and a new one is relatively inexpensive, though I wanted avoid messing with the wiring but might just have to bite the bullet and try installing a new one. Thanks for your help.

A wr2 by rain bird is,very straightforward to,install, I can send you pics of mine showing the wiring/

Can you send before/after pictures to They should be able to help with this.

Does the rain sensor have a manual button to test? This explains how to test it and see the results if it does.

When the rain sensor is tripped (activated), scheduled schedules will not run, but manually running zones will still work.


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To my understanding you can MANUALLY override the rain sensor by YOU manually turning on the sprinklers. So even though you had rain AND the rain sensor MAY be working, by telling Rachio to Manually run a zone will bypass your rain sensor. I still, however, would replace that old rain sensor as others have recommended. Cheap an inexpensive insurance . Also to see if the rain sensor is activated, just pull up the app and you should see when the rain sensor is activated and deactivated listed right there.

Yes, I understand that manually running the sprinklers would override the rain sensor in a normal configuration. However, as my old controller did not have connectors for a rain sensor, and there were no wires for the rain sensor coming out from the hole in the wall, I’m assuming that it’s wired directly into the common wire. The new Rachio controller does not know about the rain sensor as there is nothing connected to the rain sensor connectors and as far it is concerned, there isn’t one. However, if it is really connected and working to the common wire, then I’m assuming it should stop the sprinklers from working when rain is detected by interrupting the common connection.

Here is the wiring from the old Rain Bird ESP-6TM controller:

Wiring from Rachio controller:

Rain sensor outside:

I’m not sure if the rain sensor has a manual button to test, but will check later this week. Hopefully that can be used to determine if it’s connected and working.

i know im being a touch pedantic, but i would trim some of that copper off of zone 1 and 2, it looks like if you bump the zone wires some they are going to short across each other and open both valves when either zone runs.

Yeah, good point. I moved the wires around a bit to make them neater and less likely to short out. I’m reluctant to disconnect them and trim the copper as getting them into the connectors on the Rachio in the first place was an absolute nightmare and I ended up breaking the little tab above the common connector in the process (can probably see it in the picture). Fortunately, it doesn’t seem to affect anything, but I do wish those connectors were better designed to make the wires easier to connect.

Hi, new here and just installed my Gen 2 system last night.

Apologies for the thread resurrection but does anyone know what the spare blue wire in Mun’s install photos is for? I’ve just done the exact same switch from the RainBird to a Gen2 and have the same unused blue wire.

@R3dg3ckoRob - Post of picture of your wiring. It could be an unused field wire if it is in a bundle with a black case or it could be the rain sensor wire if a Hunter wireless model.

I’m guessing it’s for an unused zone. Most controllers seem to support a number of zones that is some multiple of four, and my lawn only has three zones, which are presumably the yellow, green and red wires connected to the terminals marked 1, 2 and 3.

its the exact same wiring layout as above. Blue wire looks like it’s never been used.

@R3dg3ckoRob - I*'m going with @mun and saying that the field wire had five wires in it (common plus four zones) and this is an unused wire in the system.

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