Like the others, I did the external vent thing many years ago on my previous van. I do think it worked to reduce back of fridge temps.

Caveat, it’s hard to determine the amount of the effect, none of us have set up side by side vans , with and without, etc etc , to do real tests.

Same fridge is now in my westy converted Syncro. But I don’t have the external water hook up port to use as a fan vent. And I have done lots of fooling around with mods on the fridge in its new home. Different and multiple fans etc.
 And I have insulated the exhaust pipe from fridge , the stainless corrugated pipe, with Fiberglas exhaust wrap.

I think that helps reduce the temps back there.

The incremental improvements in getting the heat away from the back of the fridge does not hugely improve things, but I think it does help.

Alistair 

> On Jul 30, 2019, at 6:22 PM, David Beierl <dbeierl@gmail.com> wrote:
> 
> ---------- Forwarded message ---------
> From: David Beierl <dbeierl@attglobal.net>
> Date: Tue, Jul 30, 2019 at 9:21 PM
> Subject: Re: Dometic Fan
> To: David Boan <dboan@outlook.com>
> Cc: vanagonlist a <vanagon@gerry.vanagon.com>
> 
> 
> 
> 
>> On Tue, Jul 30, 2019 at 9:08 PM David Boan <dboan@outlook.com> wrote:
>> 
>> I wonder what "working well" means with a dometic fridge, so I gathered
>> some numbers. ...
>> 
>> Running on 12v from the house battery, engine not running, for one hour,
>> the temp of the cooling fins inside the fridge is 49 (measured with an
>> infra-red sensor).  The outside temp, both in my garage and inside the van,
>> is 98.  The temp on the outside of the fridge door is 96 (an indication of
>> marginal cooling loss?).
>> 
>> During that hour, the house battery went from 12.5 volts to 12.3 volts.  I
>> do not have resistance or amp data to know if this is reasonable.  I
>> anticipate running this from my solar panel, which will keep the battery
>> charged during the day, but obviously not at night.  I am curious to
>> calculate how much the battery will be drawn down after 12 hours.
>> 
> 
> The fridge on DC will draw 7.5 amps continuous, with no thermostat.
> 
> 
>> 
>> I then switched to 120v.    Understanding the fridge was already cool, I
>> wanted to see if 120v would get it cooler.  After an hour the same spot
>> (cooling fins) were 40.  The outside temp was 97.
>> 
> 
> Run it for 24 hours on 120 VAC with thermostat turned to max to get your
> benchmark.  These fridges can't move much heat, so everything happens
> slowly with them.
> 
> It's been a long time, but I think box temp (not fin temp) 40F below
> ambient is doing pretty well.  Someone will correct me on that.  Keeping
> the van ventilated with the skylight for a chimney effect and shading the
> fridge side from the sun will help.
> 
> In reasonable weather they can make ice in the little toy ice trays.
> Slowly.
> 
> One of the things that will kill performance is if the fins inside lose
> intimate contact with the cooling tube.  May help to pull the fin assembly
> off, clean the old heat sink compound off both surfaces, and reinstall with
> a *THIN* I mean Really Thin layer of compound.  Ideally you want only
> enough to fill the irregularities in the apparently smooth surface, because
> heat sink compound is actually not a very good conductor.
> 
> In theory operation is equally effective on all three modes.  In practice
> DC tends to perform less well unless the wiring is absolutely tip top,
> because a half volt drop at 12V is a much greater percentage than at 120V.
> Gas normally works as well as AC.  Again, there is not thermostat on DC.
> 
> Yrs,
> d