Absorption fridge woes

[scottydl]

The Dometic absorption fridge in our 2016 Keystone fifth wheel has worked perfectly (since I purchased the trailer last year) all the way up through last weekend while camping in extremely hot weather. However, I had recently noticed it making an audible, low pitched hum… like a mechanical vibration of some kind.

I left some food and drinks in there after this past weekend, and today when I went out to get a soda… my fridge was 67° (usually 37) and freezer was 74° (usually 7). The orange “check” light is illuminated, and no switching between gas and Auto mode has made any difference. The hum is gone, so I’m assuming whatever was making that noise finally died and shut the whole thing off. It still has 12v power, as the external control unit and the internal light still function fine.

I am mildly familiar with how absorption fridges create cooling through heat, but I don’t know much about the mechanics of what makes the system work. Is there a pump in there that that’s replaceable as a DIY project? Or is this a good opportunity to cut my losses and replace with a 12v or residential unit prior to our next trip in a few weeks?

Any comments or guidance are appreciated!

 

[House Husband]

It sounds like you might have a restriction in the absorption unit.
A quick/temporary fix might be to take a 1/2 lb. ballpeen hammer and lightly tap on all the tubing and tank.
It worked for me once to get me home for a more permanent repair.

Richard

 

[scottydl]

What was your more permanent repair? I’m back home now so there’s no urgency today — just need to have it figured out before we leave on our next trip in 2 weeks.

 

[John From Detroit]

The Dometic absorption fridge in our 2016 Keystone fifth wheel has worked perfectly (since I purchased the trailer last year) all the way up through last weekend while camping in extremely hot weather. However, I had recently noticed it making an audible, low pitched hum… like a mechanical vibration of some kind.

I left some food and drinks in there after this past weekend, and today when I went out to get a soda… my fridge was 67° (usually 37) and freezer was 74° (usually 7). The orange “check” light is illuminated, and no switching between gas and Auto mode has made any difference. The hum is gone, so I’m assuming whatever was making that noise finally died and shut the whole thing off. It still has 12v power, as the external control unit and the internal light still function fine.

I am mildly familiar with how absorption fridges create cooling through heat, but I don’t know much about the mechanics of what makes the system work. Is there a pump in there that that’s replaceable as a DIY project? Or is this a good opportunity to cut my losses and replace with a 12v or residential unit prior to our next trip in a few weeks?

Any comments or guidance are appreciated!

No pump it is all convection powered. I have heard that sometimes turning them upside down (While off of course) is a "Fix" but I class that as Rumor. The usual failure mode is a leak

 

[scottydl]

No ammonia smelliness or anything typical of a leak. What would that vibrating hum sound have been coming from the back side recently?

 

[TheBar]

No ammonia smelliness or anything typical of a leak. What would that vibrating hum sound have been coming from the back side recently?

Since there are no moving parts the noise must be coming from the fluid moving past a blockage in the lines? Or a hornets nest in the exhaust vent?

 

[scottydl]

I’ll take a closer look behind the service panel tomorrow morning. I have a few theories…

 

[Gary RV_Wizard]

Do you have a fan in the cooling unit area behind the fridge? That is most likely the humming you heard. The fan would come on if the cooling unit got quite hot (and boiler overheating is the classic sign of a failing cooling unit). Your Dometic fridge has a safety sensor/switch that shuts off the cooling unit if the overheating gets severe (a fire prevention measure).

While an ammonia odor or yellow residue is a sure sign on cooing unit failure, the lack of it is inconclusive. Many failure have neither symptom. The chiller gas is a mix of ammonia and hydrogen that rapidly evaporates, so seeing or smelling it is the exception rather than the rule.

 

[Kirk]

I have a few theories…

My experience has been the same as Gary's and I suspect that your cooling system is dead. But I'd be interested in your theories as one never knows all of the answers.

 

[scottydl]

** User Error Alert **

So… my fridge is fine, at least for now. After a bunch of troubleshooting (and my wife commenting that she couldn’t get any outlets to work when trying to vacuum the RV), the brain bomb dropped that perhaps the rig didn’t have any 110v AC at all. Everything we’d turned on since arriving home last weekend had been 12v DC it turned out.

Sure enough, I eventually realized I’d connected the 30/50amp adapter incorrectly that brings power from my garage receptacle to the rig. Meaning the fridge had switched to propane for several days (plus we’d accidentally left the gas water heater on) until that LP tank ran dry. Fridge shut off and I was left scratching my head.

Power is restored and fridge cooled fine back to normal temps overnight. No buzz/hum currently either, so that remains an unknown & we’ll see if it returns.

$40-50 worth of propane and spoiled food taught me another RV lesson. I’ve been doing this since 2007 and it’s still easy to make these mistakes!

 

[8Muddypaws]

The buzzing may have been from the pressure regulator on the propane tank.

 

[scottydl]

The buzzing may have been from the pressure regulator on the propane tank.

Good thought, but I’d actually noticed that noise for the last month or so… unrelated to the last few days after our recent camping trip. At this point I’ll wait to see if it returns, and do more digging to chase it down.

 

[Rene T]

Sure enough, I eventually realized I’d connected the 30/50amp adapter incorrectly that brings power from my garage receptacle to the rig.

Scotty, Can you explain a little bit so others will understand. Maybe a picture

 

[Kirk]

Can you explain a little bit so others will understand.

I would like to hear more too.

 

[OldWEB]

Did you get into the back of the fridge? Maybe the hum are installed fans to move air in the rear.

The orange “check” light is illuminated, and no switching between gas and Auto mode has made any difference.
Was this the "Gas" light? I know ours is a steady orange light, flashes when it does not ignite.
Ignore....

 

[scottydl]

Sure - I have a dedicated 30amp connection on the side of my extra garage, that was installed ~15 years ago when the garage was built. That was great for my previous 30a rigs, but the current one is a 50a. I bought a 30/20-to-50 adapter from Amazon (Amazon.com) that produces 50 amps (or close anyway) by combining a 30a RV plug + a standard extension cord plug.

I had plugged in the 30a portion when arriving home last weekend, mistakenly assuming I’d at least get stepped down power to the rig until I could find an extension cord for the other half of the adapter. Turns out, it doesn’t produce ANY power unless both inputs are plugged in. Now I know!

 

[OldWEB]

Sure - I have a dedicated 30amp connection on the side of my extra garage, that was installed ~15 years ago when the garage was built. That was great for my previous 30a rigs, but the current one is a 50a. I bought this adapter from Amazon (Amazon.com) that produces 50 amps (or close anyway) by combining a 30a RV plug + a standard extension cord plug.

I had plugged in the 30a portion when arriving home last weekend, mistakenly assuming I’d at least get stepped down Power until I could find an extension cord for the other half of the adapter. Turns out, it doesn’t produce ANY power unless both inputs are plugged in. Now I know!

Your link shows me a "old dryer" outlet conversion. Is that the set-up you have? It says 125V, but I think that is wrong as they were 230V.

 

[Kirk]

. Turns out, it doesn’t produce ANY power unless both inputs are plugged in. Now I know!

To understand what happened you need to first understand that an RV 50A power cord has two hot pins, one neutral pin, and one ground pin. the adapter you were using supplies one of the two hot pins with 120V power from the 30a plug and the other hot pin is connected to the smaller plug.

In your situation you would have had power to one side of the RV distribution panel but no power to the other side.

 

[DutchmenSport]

If you are going from a 30 amp RV outlet to a 50 am RV camper, this is the one you should use. I agree... the one above is a 220 adapter for a clothes dryer.

Click Here.

 

[scottydl]

Don’t worry, I don’t have the dryer option… Scroll down on the Amazon page and you’ll see they sell 20+ other adapters you can select from. The link appears to have directed to a different than I have, which converts a 30a RV plug + household plug into a 50a RV outlet.

Click Here.

I have one of those too, but that just puts 30 amps through a 50a plug. My newer Y-splitter adapter essentially combines two power sources to provide closer to 50 amps for the rig. I’ve run both roof A/Cs with no issues.