Zone 2 lost on 4 button CCC

[followingsea]

hort version: Replaced A/C bedroom ducted vent with Dometic Air Conditioners 3314851.000 Adb Man Control
https://www.amazon.com/dp/B00HJQ86UO...roduct_details

Long version: Used to think that you were doing camping wrong if having a TV and air conditioner were needed.

Camping with small in a small trailer loaned out by the navy was great fun. So we bought a 16' lowliner. More great fun and better than motels between duty stations. Children get bigger so bought a new bunkhouse TT.

Without A/C!

July in 1980 found us in Tulsa OK at the KOA. A few days later on the way home from my new job, I backed the IH TravelAll to the TT and boosted a new A/C on the roof. Plugged it in, turned on, set the temp. Aaaaahhh!

When we retired on an old MH with 30 amp service. I am the proud owner of a duo-therm 4 button Comfort Control Center. Obsolete ten years later.

Welcome to the modern gadget filled RV world. At least we have the internet so we can ask for help and share experiences.

Same issue with the current MH except it is 50 amp and can run both A/C at the same time. Got another refurbished card for the CCC and was good to go. From the records from the previous owner, not the first replacement.

All is good for a few years, then zone 2 was no longer seen on the CCC. Could not run the bedroom A/C.

A frequent poster here linked a troubleshooting guide. My CCC is inconveniently located on an outside will with a heating duct blowing it.

What is the part number for the uncomfort control station?

I was able to determine the root cause. Failure of engineers to follow the KISS principle.

Option 1. Replace 4 button CCC with 5 button CCC and new cards for both A/C for $550+. This does not address root cause.

Option 2. Hire someone to find and fix a bad connection. This does not address root cause because a bad connection could occur again.

Option 3. Keep is simple stupid. If in 1980 you could control the A/C with knobs mounted on the A/C, why could it not be done the same way.

The answer is yes. First you much carefully check that wiring on the old duct and the new duct match. Since it was a Domestic roof unit I would expect inside part to match. Second, the opening to the vented ducting must be covered if you do not want to use them. Third, the holes for connecting the all thread have to me matched.


Bottom line is that I am happy with the fix for the rear A/C. If the front stops working from the CCC, I will use the same fix.

[RKins]

I think I understand the problem to be that the rear stopped working and then you lost me.
And then you fixed it and I didn't see it happen in the text.
So what was the fix?

[followingsea]

Originally Posted by RKins

...
So what was the fix?

I replaced the existing A/C return air cover for ducted systems with a cover for not ducted systems. If you look at the link in the post you will see that it has manual controls.

[RKins]

I get it now.

[MarvinG]

That’s a great work-around.

My dad had a class C similar to the install you did and the board and thermistors (or whatever) failed. The cheapest way out was I installed a window AC (line voltage) thermostat to replace all the electronics. Worked just as well as the original pieces did.

[followingsea]

Originally Posted by MarvinG

That’s a great work-around.

.... Worked just as well as the original pieces did.

I would suggest that it works better because there are few failure modes

The first thing I do when something electrical doesn't work is check fuses, breakers, and voltage. Had 120 v ac but no 12v dc.

Once I had a 19 page document, I determined that there were at 12 reasons that I might not have 12v dc.

With this fix, 12v dc is not needed. No hidden fuses that require taking apart the A/C duct.