Date:         Tue, 16 Nov 1999 14:16:44 -0500
Reply-To:     "John P. Stoneback" <jps@CS.MORAVIAN.EDU>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         "John P. Stoneback" <jps@CS.MORAVIAN.EDU>
Subject:      Dometic Fan Upgrade- Addendum
Content-Type: TEXT/plain; charset=us-ascii

Last April Bill Davidson posted his modifications to the Dometic fan. In Bill's
normal, indomitable fashion he shared with us his research and explicit
details for his modifications. In fact, after recently following his design
for installation of an Auxiliary Battery, I'm hoping Bill's next project is a
coolant pressure gage (hint).

This note details my modifications to Bill's design. For reference see

  davidson- Dometic Improvements Adding Fans- 26 April 1999

First, Bill argues that the free vent area to cool the Dometic is insufficient.
Rather than modify the grill, I opted for power ventilation. I mounted a Radio
Shack 12v brushless fan directly behind the grill facing the rear of the van.
Running machine screws through the slots in the grill- no modifications to the
grill.

I contend that my original Dometic fan never functioned. When I removed the
fridge I discovered that the thermal switch was so loose in its housing that
it likely never made good thermal contact. I threw this switch away and
replaced it with the switch which accompanies the FrigeMate fan. I used heat
sink paste as others have suggested. The new switch works fine.

Like Bill, I purchased and installed an extra FrigeMate fan. I can't recall
exact details but I used the FrigeMate mounting bracket but to keep it from
being mounted too far away from the back of the fridge, I straightened the L,
cut it off and re-bent it. If you do this, be sure you allow for the diameter
of the fan blades when you modify the bracket. Since my Dometic fan seemed to
function fine, I left it in.

My primary change to Bill's suggestions was to install three micromini spst
switches at the top of the grill where I mounted the brushless fan. These
switches, which I got from Radio Shack, mount in the grill slots. Again, no
drilling was required.

  One switch is wired in series with the thermal switch and activates/
  deactivates the entire system. This allows one to turn the system off to
  prevent the unlikely event that the cooling fans would go on when the
  fridge is not on but the vehicle is heated (from the sun, perhaps).

  A second switch is wired in parallel with the thermal switch. This allows
  one to turn the system on regardless of the temperature of the cooling fins.
  I normally do this when driving. My thought is that it may improve
  performance while running the fridge on 12 volts.

  The third switch is in series with the grill-mounted vent fan. This fan makes
  a fair amount of noise and draws more power than the others. I often have it
  on when driving but turn if off when sleeping. I wired the fan so that it
  is controlled by the thermal switch and, in series, by its own switch. It can
  be turned off but for it to be on, either the thermal switch has to be on or
  switch 2, above, must bypass the thermal switch.

All the wires running to these switches are labeled and have disconnects. You
don't want to have to fuss too much the next time you remove the fridge. The
Radio Shack switches are rated at 3 amps and should be ample for the current
drawn by the three fans.

Subjectively, I believe that the addition of the FrigeMate fan and the grill-
mounted cooling fan have improved performance of the Dometic on 12 volts. I
never had performance problems on propane but it sure lights better after
cleaning the burner.

A small bonus of this installation is that I can always tell when the thermal
switch is on by turing on the grill-mounted fan. The two fans in back of the
fridge are quiet enough so that you can't always hear them but there is no
doubt when the grill-mounted fan is running. I have actually done this at
night to make sure the fridge hasn't gone out (or I'm out of propane).
These switches are easy to reach from the lower bunk and I don't keep the
LED's on all the time.

Anyone wishing to try a similar installation is welcome to contact me with
comments and/or questions.

  John
  89 westy
                                                John P. Stoneback
                                                Computer Science Department
                                                Moravian College
                                                Bethlehem, PA  USA  18018

                                                610-861-1341 (fax 610-861-1595)
                                                jps@cs.moravian.edu