Lose wire in Dometic Duo Therm Airconditioner

mdfas · 08-07-2021, 03:28 PM

I am restoring a 2006 Rockwood HW256. The air conditioner has been running fine for about a month ( since I started going inside and fixing things ). I just noticed that after it runs for about 5 minutes I start to smell something like burning plastic so I shut it off. I replaced the filter and also there was a large mud dauber nest appended to the side. Thought that would have got it back going, but it's still starting to emit this smell after a few minutes.

Note in the picture the lose wire. What is it and how do I reattach it?

Thanks !

Matt

flyerdp · 08-07-2021, 03:53 PM

The style of connector on the end is the type that slips over something like perhaps the frame. I am just speculating here, but could it be ground and it clips over the metal framework of the AC?

At second look is it a solid metal piece that is not part of the wiring in that yellow bunch? It may well be the temp probe for the A/C. If so it measure incoming air temp to know when to shut off the compressor. Perhaps with that clip its simply meant to hold it in place?

mdfas · 08-07-2021, 05:51 PM

So I figured out the melting smell was the wire nut in the AC power supply. The lesson for me here is to replace the wirenuts and anything else that is plastic and has to do with electricity or plumbing. This camper has been sitting for 4 years ( in Texas ). I was surprised that I was able to get everything to work, but I would like to let everybody know that the plastic parts cannot withstand the kind of heat we have here. One after another is failing. I had a shutoff on the plumbing fail right away. Replaced it and then let it sit on city water for 3 days without any issues. Got all the appliances working. Then turned it back on and another plastic shutoff piece cracked.

I open the drain to the 22 gallon tank after camping to let it drain. Tried to close it and it crumbled like paper. Anyway, hopefully this will help somebody out. I love the camper, but man it's alot of work getting it going again!!

Any tips on the AC let me know. I had been running it for 4+ hours so it may heat up again. The ground looks good, but I will clean it up at least.

yes that lose wire looks like the thermostat that got detached. I dont' think it's life threatening like the wire nut, though maybe if it was clipped on correctly the AC would shut off like it's supposed to. Thanks!!!

flyerdp · 08-07-2021, 06:24 PM

Honestly, I have never had a wire nut break like that and I live in Central Texas myself.

Its entirely possible the A/C is making the wires hot and melting/softening the plastic which led to a short?! That black worries me on the wire nut.

The things I have seen fail possibly due to heat would be the sink drain tube because its flexible (swing galley) and bunk end attachments etc.... that are plastic.

I suggest you run the AC for a bit, pull power from the A/C and see if that join is warm or hot.

The sensor technically isn't a wire in the normal sense so you are right its not really an issue.

mdfas · 08-08-2021, 12:52 PM

I just wanted to complete this thread and pass on what I learned about AC maintenance. First off, the Dometic AC in the 2006 Rockwood HW 256 is awesome. It simply cools down the entire pop up in a few minutes in 95+ degree weather. I don't think you get that with most RV's.

To avoid a near fire like I almost experienced I would advise that if you have not used the pop up in say over a year, don't turn on the AC right away. I would pull off the cover and inspect the cavity very carefully. I think the melted wiring and wire nut were due to the AC having constrictions and having to overwork to pump out air.

I am running the entire camper off a single 110V plug and this AC is rated at 115V.
I have had the AC running while I work inside sometimes for over 4 hours. Last time I took it camping I had no problem running it 24/7 off a 220V plug. Anyway, two things that had constricted the airflow. First the charcoal filter disintegrated and some of it got stuck in the fins of the cooler. Secondly, I think some bugs figured out how to get in from the outside and made two large mud dauber nests appended to the cavity. I had been running the AC with both those things in the cavity.

I rewired it this morning and was able to run it for two consecutive hours and do not feel any heat inside the power supply so I think it's fixed. I love this forum. Even replies that don't lead directly to the solution give me ideas of where to look and some added confidence.

ICanFixIt · 08-08-2021, 01:56 PM

That loose wire could be the antifreeze sensor lead. The end of it would normally would be wedged inside the coil fins about 3 inches from the bottom.
I had a similar issue with melted wire nuts with one of my Dometic A/Cs. My fan motor froze up with a bad bearing and caused the wiring to overheat. Came close to starting a fire but fortunately it melted through the wire causing the wire to ground against the junction box throwing the breaker before it got worse. Normally the resistance from the motor should have thrown the breaker but the wire nut connection must have also been loose causing it to overheat. I would advise to check your wire nut connections to make sure the connections are twisted and tight before putting the wire nut on. When they install these in the factory they are in a rush and sometimes just use the wire nut to cause the twist within the nut. Not good.

On the issue with the fan motor bearing - they are merely brass bushings and not actually bearings so they do wear out. I just replaced the bushings with some bought on Amazon ($6) and saved buying a $130 motor.

**Flybob** · 08-08-2021, 02:01 PM

X2 it appears to be the coil freeze sensor. Should be clipped to the cooling fins.

Mike91 · 08-10-2021, 04:10 PM

Quote:

Originally Posted by flyerdp

The style of connector on the end is the type that slips over something like perhaps the frame. I am just speculating here, but could it be ground and it clips over the metal framework of the AC?

At second look is it a solid metal piece that is not part of the wiring in that yellow bunch? It may well be the temp probe for the A/C. If so it measure incoming air temp to know when to shut off the compressor. Perhaps with that clip its simply meant to hold it in place?

I agree, that wire nut shouldn't had burnt like that. The conductor/wire could be pulling to much current/amperage and overheated the wire, and caused arcing.

Perhaps the run or start caps are bad?? This causing the circuit to draw to much current and overheat the conductor??

I would have it checked out by a qualified HVAC Tech. Electrical fires aren't a place to save money.

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