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AC Data Cable Wiring Problem


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I lost power to my 10 Button Dometic CCC-2 Thermostat located in the bedroom.

After spending hours troubleshooting, I have narrowed the cause to a bad data cable that plugs into the back of the thermostat that snakes from side of the upper storage cabinet next to the bed to the rear AC in the ceiling. There is NO way that I will be able to snake another cable from the same location to the AC in the ceiling. It is part of the bedroom slide.

Does anyone have any ideas as to what would be a good fix for this situation?

I can attempt to replace the one end at the ceiling to see if it is a bad connector but there is not enough cable at the cabinet end to redo that connector.

I am in a jam on this plus the coach is up for sale so I do not want to jerry-rig this making it look like a cheap fix.

I appreciate any and all suggestions.

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Routing a new communication wire to the rear AC might be possible.  

Option one would be to pull the new communication wire through the AC duct.  My duct terminates right at the edge of my closet door.  I think you could pull the wire, run it along the edge of the closet doors at the top and then down to the right hand side.  If your rig is like mine I have a plastic tub in the bottom of the closet, you remove the tub and you can rout the new wire under the bed, will have to dismantle the cabinets next to the bed to get the cable up to the current location of the thermostat.

Option 2 would be to do the above but move the thermostat to the other side of the room routing the cable through the cables behind the TV & service panels. 

Either won't be easy but I think it's possible. 

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I would try using an eraser on a pencil to rub on the RJ11 connector end to clean the contacts. If that doesn't work re-terminating the ends before trying to pull new cable.

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The unfortunate situation is that I tested that specific cable with the Sperry Instrument Cable Tester that I own, and it tested good, green light. That's why it took me so long to narrow this problem down. I checked the 12 VDC supply going up to the AC, OK. I checked the 12 VAC at the control board in the AC on the roof, OK. I then went back inside to the bedroom and plug in a long data cable from the CCC-2 and ran it out the window onto the roof and plugged it into the AC control board, the Thermostat lit up. So, I buttoned up the rear AC on the roof knowing that everything up there is OK and went back inside to the bedroom and ran a data cable from the head of the CCC-2 to the coupling at the AC in the ceiling, thermostat lit up OK. So, this was telling me that the cable from the CCC-2 at the wall was actually BAD even though the Cable Tester said it was OK. Go figure. Still can't wrap my head around THAT one.

That brought me to post my situation. I still don't know if the ends are the problem or possibly some area of the cable itself is bad somewhere between the wall hole and the AC opening in the ceiling. Sometimes it is easier just to run another cable versus trying to find the bad spot if indeed it is a bad spot in the cable.

I will do some more work on it tomorrow once the sun comes up and gets a little warmer

Thank you everyone for your suggestions and feedback.

I appreciate all of them.

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19 minutes ago, vito.a said:

Usually it's the RJ11 couplers just under the A/C units (above the air filter) .  They tend to get moisture on them.

I remove the coupler, clean the RJ11 cable end connectors with DeOxit and install a new coupler.  

Hope this helps.  

What Vito said. 

I think he is referring to a coupler something like this.   Telephone In-Line 2-Way Splitter RJ11 Female Duplex Adapter (White)or like this  NECABLES (2 Pack) RJ11 Coupler Phone Line Connector Telephone Cord Adapter RJ11 6P4C Female to Female for Landline Phone and

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Richard I hope it is not a bad cable. However I have removed ceiling and wall panels in order to install new cables a few times. New T lock is available  and usually necessary as the existing deforms when it is removed. The female component is reusable if one carefully removes the T component in a gentle rolling action using a pair of pliers. On my Diplomat Monaco used 1/2" foamboard with fiberglass insulation above. The T lock is about a dollar a foot on Amazon.

Good luck

Edited by Gary Cole
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Problem solved! Yahoo!

Started with more troubleshooting on the inside this time by cleaning all of the RJ-11 connectors, couplers, etc. that go from the CCC-2 Thermostat to the AC in the bedroom ceiling. I used an eraser plus contact cleaner. Put everything back together and NO JOY. I knew that the coupler at the ceiling was good as my test wire was using that coupler plus it was the one that came with the new AC back in 2018 so it wasn't that old. Next, I went to the coupler that I use to lengthen the cable coming out of the large hole where the CCC-2 is mounted and replaced it with a new one. Voila! Problem solved!

I am thankful that I did not have to run new cable as that would have been a nightmare.

Thanks to all that responded with your thoughts and suggestions. it really helped.

Edited by Dr4Film
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