Skip to main content ↑ ↓
Topic: Dometic roof air E1 Error (Read 355 times) previous topic - next topic

Dometic roof air E1 Error

While doing my monthly running of all systems, I noticed that my Dometic Thermostat was showing E1 as it relates to the Zone 2 unit. I do have the upgraded Penguin II units, most recent road trip all was working fine. Some searching online states this is an error code for " cant see that unit" on the communication path. Common issue to be a possible loose connection, or just an occasional bug in the Tstat. Ive powered down/disconnected the Tstat, as well as i've tested the RJ11 connections and cables and getting a good signal over the entire path. But as of yet have not got on the roof to pull the main unit cover and check the other end...having some of those famous 200 deg deep south humid hot days, so would have to be a very early morning or late eve thing to do.

Has anyone seen this issue and know of any common issues to look for?

Thanks,

Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Dometic roof air E1 Error

Reply #1 –
Finally got around to fixing this issue.

As nobody ever commented or replied, I am assuming maybe I'm the first? here is what I found and what it took to resolve.

The E1 error code, on Dometic type roof AC's is a communications error between 1 or more of the roof units and the thermostat on the wall. Multiple roof units are wired in series for the communications to the 1 thermostat that controls all units. The coach came wired with RJ type connectors (5pins) that go from Tstat to front ac unit air intake box(filter), And from the Front AC filter box back to the rear AC unit air intake box (filter), and the same to a 3rd unit if the coach has one.

Inside each Roof unit is a control board with 2 smaller RJ cables (4pins) that plug into 2 RJ jacks on the boards. P1 plug is the primary that talks with the Tstat, P2 is used for going to the next roof unit. If you say have two roof units, the P2 is not used on the rear unit as there is no 3rd unit to connect it to. Inside the Air intake box the coach provided cables, splice to the Unit cables by use of a splice plug.

In the case of my E1 error code on the rear AC the small P1 cable on my rear unit had all 4 conductors open. Using a RJ cable tester easily found once I had the cover off the roof unit and the control board was removed by which to attach the tester. As I don't have a 3rd unit in our coach, I used the spare P2 cable on that unit to fix the issue. But, I did order a few 3' RJ11 phone cables as spares for the future.

I might add, at least on Dometic Penguin 2 units, the 12vdc control power is NOT provided by a coach fused source. The 12VDC is sourced from the control board outward after the 110vac going to the board is rectified and reduced. Flipping the 110vac breaker under the bed for the rear unit is all that was required on our units.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918

Re: Dometic roof air E1 Error

Reply #2 –
Thanks for letting us know what you found  ^.^d  ... thats a new one to me with all 4 conductors open.  Did you find the line was cut/broken or had the crimp gone bad?
2000 / 36' / U320 / WTFE
WildEBeest / "Striving to put right what once went wrong"
 

Re: Dometic roof air E1 Error

Reply #3 –
Quote from: steve –
Thanks for letting us know what you found  ^.^d  ... thats a new one to me with all 4 conductors open.  Did you find the line was cut/broken or had the crimp gone bad?

Shocker for me also, as I worked in industrial automation for many years and dealt with RJ and CAT cables every day. Almost daily we would deal with the loss of say 1 channel but not all of them. Both RJ and CAT type cables are poor quality choices for any situation with any vibration at all, Yet our coaches are full of them. Probably why so many new coaches these days are having electrical/communication issues. To simply re-crimp usually does no good, as the problem is not so much the crimp point as it is the fact the original crimp was too tight and more than likely near severed the strand, which ultimately broke. The old RJ crimpers did not have a calibration point for pressure and over crimping was always an issue. Most new CAT crimpers do, but can do the same thing IF the user doesn't occasionally check the tool for bite depth.

  The OE cable is actually inside of a larger plastic sleeve and from what I could tell no issues anywhere. I might add, that even though there are 4 conductors, only 3 were active (guess that is all that is needed), and this included the cables on my front unit as well as I tested all of them. The new spare RJ11 cables I bought show all 4 channels active. Just like having a few spare compressor/motor start capacitors on board, having a spare RJ cable or way to retip aint a bad idea as cheap as these items are.
Mike in AL
2001 U295
8.3 ISC 350
Build 5918