Yes, the by-pass wire is equilivent (electrically) to the rain switch. The by-pass wire is just a jumper; a short piece of solid core wire connecting two terminal points. The terminal block on the output board (upper right side) is marked by-pass. You can check the rain detector with a multi meter. Remember the rain sensor is adjustable. You may need to adjust it to respond to different levels of rain.

Thanks GardenGuy. I am aware of the adjustment on the irritrol rain detector/transmitter (outside my house). The Irritrol wireless receiver (wired to my timer) lights up appropriately (green power light on; green signal light on; red rain light on during precipitation). The Irritrol reciever does have a "smart bypass" switch--I think this a manual switch to activate the rain delay--even if it's not raining? What sort of electrical signal should I be able to detect using an ohm meter? If I disconnect the 2 red wires from the rain switch which are currently connected to the jumper terminals, should I be able to detect -/+ continuity depending on dry versus wet?

Many Thanks

You can test the rain switch using an Ohm meter. The red wires should be connected to the two 24 vac power terminals, keep them connected. Disconnect the brown and the white wires from the two sensor terminals, these are the switching wires. When the switch is not activated you should have a SHORT condition across those two wires. When the switch is activated, you should read an OPEN condition across those two wires. If it is switching, the problem is the timer, if not the problem is the rain switch. Keep in mind that the Custom Command will override the rain switch in a MANUAL start, also make sure that the Rain Switch Bypass Switch is in the ACTIVE position.