Why doesn't my 'fridge work well on 12v?

[TMG51]

My van has a 3-way refrigerator: 120v AC, 12v DC, or propane.

Works great on propane. I fire it up and stuff gets cold within an hour. The freezer even freezes.

I'd like to be able to run it on 12v though and take advantage of my solar so I'm not using up propane all the time. When I set it to run on 12v, the pipes and such on the back of the unit get warm, so I know it's "working," but items inside don't get cold. At least not noticeably. The unit is about 16 years old now and I have no idea if it's ever been serviced. Should I take it to a tech? Am I going to get my money's worth? I took the back panel out and couldn't see anything obvious that needed cleaning.

 

[Bela's Mom]

I have a similar fridge in my van.  Running the fridge on 12V is only intended to keep already cold items cool while driving.  Running it on the house battery or the chassis battery without the engine running will deplete the battery in 2-4 hours.

There is a 20 amp fuse in the back that runs between the battery and the little electrical block.  You might check to see if it is blown.  Mine did not appear to be blown because it was blown below the metal contact on the glass fuse. 

You might put a multimeter on your battery and check the voltage.  Then turn your fridge on 12v and see if the voltage drops.  If it doesn't, maybe the fuse is blown.

When boondocking, I run mine on propane. It only requires .5 amp per hour for the 12v requirement on propane. It will take alot more to try to run it off of your battery alone, even with solar.

 

[Almost There]

16 year old fridges are power hogs to start with!

As Bela's Mom said, the 12 v on the RV fridges was only designed for running down the highway, not for continuous use. It was expected that once you were parked you had access to 120, use the generator or switch to propane.

If it's running on shore power and on propane, there's not much else that could be wrong on 12v except for the fuse or the 12v line running to the fridge from either the power center or the battery.

 

[Optimistic Paranoid]

My van has a 3-way refrigerator: 120v AC, 12v DC, or propane.

Works great on propane. I fire it up and stuff gets cold within an hour. The freezer even freezes.

I'd like to be able to run it on 12v though and take advantage of my solar so I'm not using up propane all the time. When I set it to run on 12v, the pipes and such on the back of the unit get warm, so I know it's "working," but items inside don't get cold. At least not noticeably. The unit is about 16 years old now and I have no idea if it's ever been serviced. Should I take it to a tech? Am I going to get my money's worth? I took the back panel out and couldn't see anything obvious that needed cleaning.

Have you tried searching on the web for a downloadable manual for your particular make and model fridge?

I think the other two responses you got were right.  Household fridges use electric to run a motor and compressor.  RV fridges use propane and electric to HEAT the working part.  They were really designed to be run off 120 volt AC at campgrounds, and off the propane if boondocking.  The 12 volt DC heating element probably wasn't designed to be that effective.  Might be possible to upgrade it, either with a special order factory part, or via redneck engineering.

Regards
John

 

[TMG51]

Interesting. I guess I thought 12v cooling was possible. Maybe I'll look into upgrading my 'fridge some day.

Although with it on 12v all day long in the sun my battery level stayed good with 200w of solar on the roof. Maybe I'll try cooling with propane, then turning the 12v on a while.... when I left the propane on constant it used about 1/2 of the on board bottle in a weekend. But I don't think I realistically need it on constantly.

 

[Almost There]

Interesting. I guess I thought 12v cooling was possible. Maybe I'll look into upgrading my 'fridge some day.

Although with it on 12v all day long in the sun my battery level stayed good with 200w of solar on the roof. Maybe I'll try cooling with propane, then turning the 12v on a while.... when I left the propane on constant it used about 1/2 of the on board bottle in a weekend. But I don't think I realistically need it on constantly.

To the best of my knowledge, even newer 3 way fridges are not designed to run efficiently and continuously on 12v.

If you really want 12v refrigeration then the compressor fridge/coolers are the way to go.

It will also work better and take less energy to run if the back side of the fridge is not facing the sun. A lot of RV's have the fridge on the drivers side of the kitchen which has no awning there to provide sun. The insulation in behind the fridge is most often lacking or non-existent and in the full daytime sun heat builds up both from the fridge operation itself and from the sun making it almost impossible for the fridge to stay cold. It will then run constantly eating up either solar/battery or propane.

If it indeed is on the drivers' side then providing some shade might cut down on your energy use.

 

[Almost There]

A late edit!

It should read:

A lot of RV's have the fridge on the drivers side of the kitchen which has no awning there to provide sun
shade.

 

[Optimistic Paranoid]

BTW, Google "RV Refrigerator Fires".  Certain makes and models are known for causing a rash of RV fires.  There's at least one class action lawsuit over it, and I believe there are special automatic fire extinguisher systems available designed specifically for mounting near these fridges. 

Regards
John

 

[Bela's Mom]

Mine barely uses enough propane over several days to move the monitor, even at the beach in the sun.  You might want to have it checked out.

 

[ccbreder]

16 years old. uses too much propane, doesn't work on 12 volt heater. Sounds like you need a new one.

 

[highdesertranger]

on 3 way refers the 12v part is only meant to run the refer while driving. the 12v heating element is marginal at best. you also know that you are not supposed to run the propane while driving(illegal) also while refueling(also illegal) in fact your propane is supposed to be shut off at the tank when refueling. highdesertranger

 

[TMG51]

Mine barely uses enough propane over several days to move the monitor, even at the beach in the sun.  You might want to have it checked out.

16 years old. uses too much propane, doesn't work on 12 volt heater. Sounds like you need a new one.

Hmmmm. Interesting. If I got a couple weeks out of a fill I would be thrilled with that. I guess I'll have to look into what to replace it with.

 

[highdesertranger]

if you replace it and you have solar go with a 12v compressor refer. there are several that are direct replacements for the old 3way refers. highdesertranger

 

[ZoNiE]

A 12V computer fan to push the heat up and out the top vent of the compartment helps a lot. Many installations don't have proper venting to allow for proper bottom to top convection.

At the end of the day, the other responses are correct. Compressor models are much better if you have at least 300W of solar.

 

[TMG51]

if you replace it and you have solar go with a 12v compressor refer.  there are several that are direct replacements for the old 3way refers.  highdesertranger

Does anyone know where I can find a reference of compressor style replacements? I can't seem to find anything. I seem to mostly only find top-opening chests.

The fridge is a Dometic 2333. The manufacturer lists replacement options that are 2 or 3-way absorption. 29 3/4H 20 1/2W 21 3/8D

 

[Optimistic Paranoid]

Refrigerators for boats are all compressor style - I don't think they're allowed to use propane fridges on boats.  Here's one example:

http://www.westmarine.com/buy/norcold--de-0061-ac-dc-refrigerator-freezer--5388699

Regards
John

 

[TMG51]

If that one fit I would be sorely tempted! I think I could make this one work though.
http://www.westmarine.com/buy/norcold--3-6-cubic-ft-refrigerator-freezer-de0078--10899169
Guess I should be looking at marine refrigerators. Thanks for the tip.

 

[TMG51]

Wow or all these. Much better reviews.
http://www.westmarine.com/buy/isotherm--isotherm-cruise-refrigerators--P011020443

 

[eDJ_]

A friend of mine had a Winnebago Lesharo that was having problems with the refrigeration.

He got it serviced, mainly a good cleaning, and it worked almost too good afterwards.
He and his wife were going to Myrtle Beach, SC and loaded the fridge with cold foods
and set out with the 12v running as they went down the road driving straight through.

When they got back he told me everything in the fridge had frozen,  like the fridge
had become a freezer.

Here's an overview of how these absorption cycle refrigerators work.

http://www.rvdoctor.com/2004/02/rv-absorption-refrigeration-basics.html


http://www.rvdoctor.com/2004/02/rv-absorption-refrigeration-basics.html



An animation of this process



http://www.hvaceducationaustralia.com/Resources/Images/Absorption System.gif



His outfit worked on Propane, 115 volt AC, but not so great on 12 VDC sitting in the driveway.
But when on the road and underway the 12 VDC did a good job.  He had to stop and check
to see that it wasn't freezing things on longer trips.  Often he turned it off  for an hour or two
before turning it back on when underway just so his stuff wouldn't freeze.  I don't know if this
is typical or if others have experienced this with their outfits or not ?

 

[ZoNiE]

http://truckfridge.com/models.html