Eaton Cooper RF9640 3 Way Synchronization?

Hi - one more observation and I feel like you will know the answer to this. It’s not a big deal, but one thing I noticed is that when I turn on the Eaton master Dimmer 9640 and the accessory Dimmer 9642 is off, the master dimmer does not turn the accessory dimmer on. So if I then want to turn off the light from the accessory dimmer, I have to press the button twice, once to turn it on and then again to turn it off.

I suspect this is a hardware limitation. Since the master dimmer cannot control the accessory dimmer, there is no way to tell the accessory dimmer to turn on at the same time that the master dimmer turns on.

Again I can live with it, but was curious if this is a common issue. Maybe now that the accessory is associated to the master, I can solve for this with a routine :thinking:

Under the independent third-party Z wave specifications, it should be your choice. If you want the master to turn on the accessory, you just create an association going the other way.

Most of the time, this is not a problem, and does not create a feedback loop. you can turn on either switch and the other switch turns on.

There have been some reports by some users that they did get looping, but my own hypothesis on that has usually been that they had set up Multiple Loop Controls, one with direct association, and one with Automations in the app, and it was sometimes a timing issue. I can’t prove that one way or the other, though.

But you can certainly try setting up an association in the other direction and see what happens.

In that case, the master is the trigger, and the accessory is the target. So you would be configuring an association group in the master, so that it would list the device ID of the accessory.

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I take it from this that, in the Eaton brand, the accessory dimmer has its own Z-wave radio.

I’ve got Leviton Z-wave, Zooz Z-wave, and GE/Jasco ZigBee devices set up as three-ways. Each with its proper accessory dimmer, of course.

For all those brands, the accessory dimmer is a dumb device that uses the traveler wire(s) to communicate with the master. Zooz uses the original dumb switch for three-way so you can only adjust dim level at the master.

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Eaton Z-Wave 3 way switching can be done in 2 ways.

You can use the traveler wire and a dumb switch or you can use Z-Wave association with a smart auxiliary switch.


When you use the traveler option the traveler wire goes to the dumb switch and the other terminal on the dumb switch can be connected to the hot wire, neutral wire or ground wire per the manual. So you don’t need a neutral for the traveler. I use the neutral and the traveler is a low voltage installation.


Yup you are right. I did exactly what you said. It worked. No feedback loop. Thanks so much!!


Yeah just set it up going the other way and it worked. I was originally disappointed in the Eaton switches as they are not exactly user friendly, but in the end they worked out. They look pretty sharp too.


Gotcha. Yes I was told by Eaton that 9640 master can only work with the 9642 accessory using associations. Apparently, people were having lots of trouble with this so they recently released the 9643 master which allows you to use the traveler wire and a dumb switch (albeit for some reason Eaton told me that the dumb switch could not be a dimmer). Not sure how true that is as the individual that I spoke to at Eaton did not sound very confident with his advice.

Unfortunately for me, I did not find out about the 9643 master until after I purchased two 9640 master dimmers and two 9642 accessory dimmers, and had already installed them. So I was committed to figuring out how to get them to work, which I was able to do today thanks to all the help from this amazing forum.

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I would guess that the dumb auxillary switches are strictly on/off, not dimming.

I don’t have any Eaton dimmers so it is just an educated guess. All my Eaton devices are on/off switches, outlets or plug in sockets.


First rule of home automation: the model number matters. The older model Eaton Cooper dimmers, such as the OP has, can only support RF 3 ways. Some of the newer models do allow the use of a physical traveler wire.

@Tom11 it is quite common for RF masters working with a traveler wire-connected accessory to only allow on/off at the accessory, not dimming. That’s because the on/off just requires a pulse to travel along the traveler wire, the physics are pretty simple. To allow dimming from the accessory you have to synchronize the level, which is much more complex. So most Z wave masters do that with Zwave association, not a physical wire connection. This is true for all brands. :sunglasses:

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Ahh, that makes sense. So, in the end I am glad I stuck to it and figured out how to set up with associations since I ultimately have more functionality by being able to dim at both ends of the hallways.

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I believe my GE/Jasco’s use a paddle switch with a traveler and I can dim from there or the dimmer switch.

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Yep. That’s why I said “most,” not “all.”

Again, the model number matters. :wink:

In the case of the GE models, which are dumb devices without a zwave radio, when you hold the accessory switch down it sends a continuous current flow to the master, which interprets that as a dim command. Note that for those models it’s not a true synchronization: the master just starts from whatever level it’s at and then goes down for as long as the traveler wire has current (or it reaches 0%).


The Eaton Cooper RF9642 accessory is itself a smart device. It has an 8 step LED indicator display in the upper left. If it used the same method as the GE, pretty soon the indicator lights on the two switches would get out of synch.


Zwave direct association for multilevel devices includes the step level in the command, so the two devices will actually be synchronized, making the indicator lights the same.

So, different features, different methods. :sunglasses:

Makes sense…and I defer to you as the Z-Wave Master :wink:

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Just a former field tech, but thanks. :sunglasses: Having to actually make things work rather than just design them back at the office does keep you alert to the practical details! LOL!

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Both GE/Jasco and Leviton require specific accessory dimmers for n-way use that have no radio.

Both brands allow dim level control from the accessory dimmer.

I have multiple pairs of Leviton Z-wave dimmers/accessories and a couple of different models of GE/Jasco ZigBee dimmers/accessories.

Edit: didn’t read to the end so didn’t see @JDRoberts comments about the GE/Jasco internals.

The Leviton DD00R accessory dimmer has no radio. But it does have the same small secondary rocker to control the dim level and same row of LEDs to show the current dim level. Once installed the appearance and operation of the two sides of the 3-way are identical.

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Yeah My RF9642, looks slightly different (see below), but I think it works the same as the one in your picture. Also when you say “multilevel” that is not to be confused with “multi-channel”, just in case others are reading, since my RF6942 is a single-channel device.

Screenshot 2023-03-31 173409

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Right, Eaton offers two styles of these models, “Designer” and “Decorator.” Both have the step level LED indicator, I just thought it was more obvious on the one with the individual dots. :sunglasses:

And, yes, in the independent third-party Z wave specifications “multilevel“ means a dimmer or other device, which allows for multiple values, not just on/off, and “ multichannel“ means has multiple endpoints.

Some devices are both multilevel and multi channel, but the RF9640 is single channel multi level.

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Hi @Tom11

Although it is not a multichannel device, many support multichannel association, since they might need to send association commands to other multichannel devices and you have to use that command class to introduce the destination enpoint of the commands.


Hi All - So the latest update on the association of my Eaton RF9642 Accessory Dimmer with my RF9640 Master Dimmer is that last night I noticed that the RF9642 suddenly stopped working. It shows offline in the ST app and is unresponsive to physical button presses.

It is effectively stuck in the “on” position and the light display on the switch is frozen (e.g. pressing the dimmer up/down does not move the blue light up and down on the switch.) I tried holding down the on/off button for > 30 seconds to see if I could manually factory reset it, but it remains frozen and stuck in the “on” position.

The master RF9640 works fine. It functions properly both manually and within the SmartThings App. Any suggestions? The RF9640 has a small tab that you can pull out to manually cut power to switch, but this tab does not exist on the RF9642 model.

Should I try to manually remove the RF9642 from the SmartThings App? If I do this I worry I will not be able to ad it back since the switch is currently unresponsive so there will be no way to pair it to my hub

I also tried repairing the Z-Wave network and let it run overnight, but when I looked at the status in the morning it was still running. I suspect this is a totally separate issue, so I don’t want to try to solve this one for now. The rest of my 25 devices are working properly both with physical touch and via the SmartThings App. It is only the one RF9642 Accessory Dimmer where I have an issue


I would try turning the power going to the switch off and on using the circuit breaker.