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toddspeed 04-30-2021 09:56 PM

Eplex, HVAC, and 5 button controller option
Resurrecting this thread from the dead:

I just purchased an 06 Essex (eplex) and only had one HVAC unit (zone 4) working when I got it. 90 deg sunny day here at Daytona Speedway and it was getting unbearable. I had purchased the 5 button controller after reading the thread linked above and had been meaning to try it as a means of troubleshooting since two of my room thermometers were reading 50deg or more off (one is pegged at zero). I wasn’t sure what the issue was but fans wouldn’t run nor would any other mode work in zones 1 and 2.

I plugged RJ cable above the driver into the 5 button controller and got code EE, which from another thread I found I needed to hold the mode and zone buttons while turning the controller on. Then boom I was able to get all 3 zones working properly for the first time.

Which still begs the question as to why they weren’t working on eplex. I suspect the 2 room thermometers that are reading incorrectly could have something to do with it? But even the fans wouldn’t run before which I think have nothing to do with thermometers. Possibly need to repair the RJ connectors at the roof units themselves? If so not sure why the 5 button allows them to work properly thru the same RJ connection.

It does seem like the temperature is now controlled by the 5 button. I had it in the upper cabinet above the driver and it was quite warm up there. The ac stayed on well below the set point. When I moved the 5 button out of the cabinet into the room air, all 3 ac shut off within a few minutes. So it seems like the 5 button controller is also acting as a single room thermometer for all 3 HVAC zones. Which is better than nothing but doesn’t really “zone” the coach anymore if you wanted the bedroom colder than the living area, for example.

Or is all this simply the sign of an eplex system on its way out? All other functions seem to work great. Do I neeed to just get new room thermostats for eplex or is it the RJ connectors on the roof or both?

Anyway, huge thanks to whoever figured this out!

azSkier 05-01-2021 09:31 PM

Your eplex is old, obsolete and on its way out. I replaced mine several years ago. Recommended.

You are correct that you now have a 1 zone system. The eplex temp sensors are not used by the dometic controller. You will need to add 3 more dometic sensors to get the 4 zones to work again. See my posting history for details.

If the new controller is working, then the rj connections are fine.

Good luck. Once eplex is removed, your coach will work fine.

DandyDon 05-01-2021 10:01 PM

In reading this and other related threads, and checking my coach's controllers, it appears I do not have the eplex system in my 05 Essex. No touchscreen anywhere that I can see, but then again, I don't even know what I'm looking for??

azSkier 05-01-2021 11:37 PM

2006 was the first year for eplex. Todd needs to make his essex operate like yours.

DandyDon 05-02-2021 03:58 PM


Originally Posted by azSkier (Post 5734599)
2006 was the first year for eplex. Todd needs to make his essex operate like yours.

Gotta feel badly for Todd, but I'd say it's good news for me. It's been 5 years that we've been spending eight months or so a year in a motorhome and I haven't even begun to scratch the surface as far as a learning curve. Most everything I do know I've learned here!!

toddspeed 05-03-2021 06:58 PM

The plot thickens.

I found a binder with sooooo much e-plex info. It looks like it was a factory presentation back in the day. It has hand written addresses and clock info and where each module is located.

I figured out I have 3 bad modules. One for fresh water tank level, one for hvac interface, and one for zone 1 thermometer.

Looks like if I replace those 3 modules it will all be back up and running!

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