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Dometic..It controls the Atwood hydro-flame 8900-III..AC..RV…

I have a Dometic Duo-Therm...
I have a Dometic Duo-Therm IR remote control in my 2006 Keystone Cambridge RV. It controls the Atwood hydro-flame 8900-III-LD furnace and the AC unit. Last year when I opened the RV the remote wouldn't operate the furnace or AC unit. The wall-mounted receiver, in spite of good batteries in the remote and no fuse or circuit breaker faults, would not respond to the signal from the remote. I also couldn't override the system with the buttons on the wall-mounted receiver. I took the wall unit out and I think I disconnected the phone-type jack. When I reconnected it, the unit appeared to work the next time I tried it. It worked flawlessly the entire season. I closed up the RV for the winter and this season the same problem presented itself. I haven't tried disconnecting the wall-mounted phone-type jack yet. Any ideas why this system is malfunctioning and what I can do to fix it?
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Answered in 6 hours by:
5/20/2010
RV Mechanic: Randall, RVIA Certification replied 12 years ago
Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 28,711
Experience: RVDA/RVIA Master Certified Technician with many years experience.
Verified
Hi: Thanks for coming to Just Answer with your question. My name is XXXXX XXXXX perhaps I can assist you with this. The problem is caused by a voltage drop when you aren't using the coach in the control box in the ceiling unit. This has a computer board just like your home computer in many ways and doesn't work properly when the voltage drops or varies much. When you disconnect it that allows it to reset itself. They have had lots of problems with this and aren't making it any more. The parts are getting harder to get so if you like yours and don't want to upgrade the whole thing you might want to get some spare parts. If you need the manual for the reset and operation go HERE for a copy. Hope that helps. R.J.
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Customer reply replied 12 years ago
Whe you say "the control box in the ceiling unit" are you referring to the roof-mounted AC unit? I have no access to this unit through the ceiling of our RV, (only from the roof). When you talk abut "disconnecting the control box" are you referring to when I unplug the phone jack from the back of the wall receiver? What exactly are they "not making anymore?" Would I need to replace the entire AC unit or just this "control box" in it? When you say "if you like yours and don't want to upgrade the whole thing" what specifically are you referring to? What option would give me the most cost-effective fix for future trouble-free use of the HVAC system? (I have a pretty good working knowledge of things electromechanical in nature and wouldn't be afraid of tackling the repair if I knew what was needed).
RV Mechanic: Randall, RVIA Certification replied 12 years ago
Go HERE for the complete Service Manual on Duo-Therm A/C units. If you go to the proper section you will see the control box which is accessed under the ceiling grill. It has the various test procedures so you can do these yourself. You can disconnect the power and not the actual box. The A/C is fine......the later style control system comes in a kit. I think it does away with the remote and just uses a wall mounted t-stat instead. I just wanted you to know that if you like the remote setup you need to try and get a few spare parts as they are NLA in production. If the remote isn't a big deal then wait until it breaks and get the new style. You can install this yourself as it is all "plug and play" stuff. Hope that helps. Get back to me if you have any more questions. R.J.
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Customer reply replied 12 years ago
Again I say, I have no ceiling access in my RV. There is no grill underlying the AC unit. All I have are ducts embedded into the ceiling of the RV. My only access to the AC at all is by removing it's cover on the rooftop of the RV. Since the original components are still present since purchase of the RV, I can only assume at this point that the AC unit is a Duo-therm unit, but I haven't tried to get a model # XXXXX of it yet. I'll try to do this over the weekend when I'm at the camper. I'll give you a progress report early next week.
RV Mechanic: Randall, RVIA Certification replied 12 years ago
I have never seen an A/C that didn't have the air intake grill right below it. Yours would be the first. The control box is right underneath it. It will be right under where ever the receiver is. Is the receiver not on a grill? I will watch for your post.........R.J.
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Customer reply replied 12 years ago

You can verify with Keystone if you like, but there is no air intake beneath the AC unit. Everything is ducted. The IR receiver is on the wall between the kitchen and bedroom of our 5th wheel and it looks exactly like the one in Dometic's Duo-Therm IR operation manual. All air intake for the AC unit is via ceiling ducts. That control box that you speak of must be accessible somehow when the plastic AC shroud is removed from the rooftop. The phone-style jack installs into the back of the wall-mounted IR receiver at one end, and, presumably, into the control box at the AC end. I suppose I could look for it at the AC unit once I pop the cover off of the roof. I need to figure out if the control box is the issue, because if it is and needs replacing, I'll need to know how to locate it. It also sounds like the diagnostics are all located at this box. Am I on the right track with this?

RV Mechanic: Randall, RVIA Certification replied 12 years ago
Well, as I said.........this would be the first one I have heard of. Sounds like you are describing it properly. The Control box which is shown in the manual must be under the cover as I don't know where else it would be. There may be one shown in the manual that way I I just missed it. I will take my copy and go back over it this weekend while I am off. You can test it however by doing that one shown in the manual where you take a standard phone jack outlet and plug it onto the cable and then take a voltage reading. That would save you having to access it unless it is bad. Most of the time the problem is in the receiver itself, but I have replaced about a dozen or so of the control boxes. Cutting off the power will reset the unit as you found out. I would hope that they wrote the model number of your unit in the manual someplace if you can't see it. I don't know how they are holding it on as the bolts usually are accessed from the ceiling grill. Changing this unit out may be a challenge if you have to do that someday. All A/C units I have ever seen are mounted on the same sized hole as the standard 14" square roof vent. I will be interested to see what you find. R.J.
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Customer reply replied 12 years ago
I'll update you after the weekend, or sooner, if possible.
RV Mechanic: Randall, RVIA Certification replied 12 years ago
I will watch for your post..........
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Customer reply replied 12 years ago
I popped off the plastic shroud and found the control box mounted onto the fore-facing surface of the metal housing of the AC unit. The Model # XXXXX the Duo-Therm AC unit is: 59516.531, serial # XXXXX 31758. The control box part # XXXXX:(NNN) NNN-NNNN004, with serial # XXXXX (Do those numbers mean anything to you re: am I describing the correct items?) I have 120 V.A.C. entering the control box but when I ran the diagnostics on the 6-pin connector of the box with a light bulb as described on page 40 of the service manual, none of the pins showed any sign of power when co-connected to the #5 pin of the connector. I was also not able to get any power at what is referred to as the "comfort control center" (sounds like my receiver unit on the wall) when I ran the test for DC power, as described on page 52, figure 53C. I tested good continuity in all 4 wires of the flat phone cable that runs from the control box to the comfort control center. I neglected to check for 10-16 volts DC entering the control box through the red and black wires entering the control box, however, so I guess I'll need to do that first before I can go much further. I don't know if I'll be able to get back to the RV before next weekend to do that test, but if I can, I'll update you on the results. Any other suggestions when I go back?
RV Mechanic: Randall, RVIA Certification replied 12 years ago
Check to be sure you have power going into the control box. The(NNN) NNN-NNNN004 is the one. Then check the phone cord coming out to see if you have an DC to the receiver. Let me know what you find. I will watch for your post. Bookmark this to come back to it easily.
R.J.
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Customer reply replied 12 years ago
I have 13.7 V.D.C. into the control box and 120 V.A.C. in also. The power in seems fine. I have no power going out of the box at any of the circuits for fan, compressor, etc., and no power to the thermostat/IR receiver. Seems like the control box is shot, but will I need to replace both the box and get a new thermostat too? Can you advise me re: locating replacement parts for this unit, given that the original parts are no longer in production? Is there anything else in the diagnostic troubleshooting algorithm that I should be looking at or is this enough info to make the diagnosis?
RV Mechanic: Randall, RVIA Certification replied 12 years ago
I would concur with your diagnosis with what you told me. You may be able to get a control module only. I would check HERE for that. These people keep a good supply of parts and when I worked in California last year we ordered all our parts like this from them. Good prices and no tax. I also called my old boss and they have the complete kit with the new remote as well. That is part number(NNN) NNN-NNNN009 and you would need to call(NNN) NNN-NNNNand ask for RV John. That is $169 plus tax and freight to your location. Let me know if I can be of any more help on this. R.J.
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Customer reply replied 12 years ago
Thanks for the input. I have the complete kit ordered and it should be available at a local RV dealer on Friday morning. If I can pick it up that day, I'll install it over the weekend and give you an update on the results early next week. I'm feeling fairly confident that this should resolve the problem. If it doesn't, I'll let you know. (P.S. The RV dealer tried to sell me an entire new AC unit to solve the problem. Go figure).
RV Mechanic: Randall, RVIA Certification replied 12 years ago
How did the price compare to the one I mentioned? And yes, some dealers are not that interested in repairing units........just selling new ones! That is one reason we stay so busy here! Sure beats paying about $100 an hour at someplace that just wants to spend your money........Let me know how it goes. R.J.
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Customer reply replied 12 years ago
The dealer's price to me was $149.95 plus shipping, handling and tax, so it will probably be comparable to your figure. I'll update you when I pick up the parts and install them, hopefully, this Friday.
RV Mechanic: Randall, RVIA Certification replied 12 years ago
Good price.........I will watch for your post. You can Bookmark this and come right back to it at any time. R.J.
Randall
Randall, RVIA Certification
Category: RV
Satisfied Customers: 28,711
Experience: RVDA/RVIA Master Certified Technician with many years experience.
Verified
Randall and 87 other RV Specialists are ready to help you
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Customer reply replied 12 years ago
Picked up the parts. Turns out they were $149.95 out the door with no extra costs attached. Problem solved!!! System worked fine once I figured out how to decipher the conflicting information in the ops. manual for the remote vs. the instructions supplied in the service manual for the configuration of the dip switches that allow the system to work properly. Thanks for your help with this one. I'm sure that you saved me a fortune in repair costs.
P.S.: You'll probably be hearing back from me in the future re: our reefer unit, which also developed "issues" this season. I'll take a crack at it first and if I can't get it right I'll be in touch . I'd highly recommend you to anyone with an RV problem. You're clearly knowledgeable, responsive to needs and a pleasure to work with. I also appreciated how you went the extra mile for me by contacting your old boss re: parts availability, costs, etc.
RV Mechanic: Randall, RVIA Certification replied 12 years ago
Thank you for your kind words.........much appreciated and so is the bonus! Always great to work with people who are patient with the process and the limitations. Most of the time we can save you a ton of $$$ and that is never a bad thing. I got on here after asking a question about my Rivera that the dealer wanted over $500 to "check out" and it took me about $15 and 15 minutes on Just Answer to get it solved........sold me! Come back any time and you can always ask for me personally. Best2u, R.J.
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