A/C lines freezing - rattling

Hi All,
  Have a new 2020 264BH travel trailer with a Dometic 13,500 BTU A/C.  We've been having a problem where the A/C would make a loud rattling noise 'sometimes' after it ran for a while.  On our last trip it did it on and off from 2AM until 5AM when I finally gave up and turned it off.  I've had it into the shop twice and they cannot diagnose.  I figured it out today when it was hot (90F) and humid, but not sure what to do next.  What's happening is that the cold suction copper line coming from the evaporator going to the compressor gets covered with ice and starts to vibrate excessively.  When it does this, the bottom bend of the copper line hits one of the mounting screws and bangs on it, echoing throughout the camper.  When the unit is off, the line is less than 1/4" from the screw.

1. In my limited experience with home and auto air conditioning, the suction/return line is always insulated to prevent condensation.  Do they skip that in R/V systems since they are so compact?  Or is this a manufacturing defect?
2. Where the line has vibrated into the screw, it is now dimpled or eroded from the movement.  Should I demand that this line be replaced since it would be a weak spot in the future?

I'm expecting that the tech at the shop is just going to grab the line and bend it away from the screw, problem solved for him.  But then I'll have problems down the road that I shouldn't have on a new system.  Before I figured out the cause of the noise, I was planning to insulate the lines myself which would have solved the problem.  Except that I was doing it for cooling reasons and not for clearance reasons....

Thanks!
+Doug

I think it is low on refrigerant and they should replace the unit.

A (very) dirty filter or dirty evaporator can cause this.

ChasA said:

I think it is low on refrigerant and they should replace the unit.

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Ditto that is a sign of low refrigerant.

Get a leak detector and check for leaks especially where the screw damaged the line.  Harbor Freight has a cheap one if you can't borrow one.  Remove the air filter and check all outlets to be sure that air flow is not restricted.  Take down outlets and look inside using a flashlight and mirror to see the condition of the ducts.  You might need a new AC but you still need to know for sure that the air flow is good.  Depending on others will get you nowhere.

This is a warranty problem and it should be handled by your dealer.

When you take it in for repair, focus the complaint on the freezing lines, and oh ya, it rattles.  I agree with others, a new unit, should not ice up.  On a modern house unit, there is a defrost cycle, I'm not sure if Dometic RV unit does the same.  Might be a simple board issue?

ChasA said:

This is a warranty problem and it should be handled by your dealer.

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I believe he already had the geniuses look at it twice and is hesitant to turn them loose on it again.

Find a good mobile repair guy who will work with Dometic to solve your problem .
Most RV dealer repair guys are lacking in refrigeration skills

lynnmor said:

I believe he already had the geniuses look at it twice and is hesitant to turn them loose on it again.

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What's to diagnose? The A/C is most likely still in warranty. Get them to replace the unit.

I've carefully bent A/C lines away from interference points on RV's a number of times over the years to eliminate vibration noises. They usually don't need much more clearance to stop the noise. As for the line icing up, that's not unusual in humid weather and as long as the condenser isn't icing up should not cause any performance issues. Insulating the line with foam pipe wrap will help though. Running the fan on high in humid weather will minimize condenser icing.

Thanks to all for the excellent advice.  It reinforces my thoughts.  Also appreciate that everybody lives up to the heading of the "friendliest place on the web for anyone with an RV". 

I'll probably start with tech support at Dometic and get their advice since it is in warranty.  They may be able to recommend an experienced and knowledgable repair shop.

Good news, Dometic agreed to replace the entire A/C unit.  Thanks to all for the good advice!

That's great to hear.  Thanks for posting  )