Date:         Tue, 27 Apr 1999 16:06:11 -0400
Reply-To:     David Beierl <synergx@IBM.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <synergx@IBM.NET>
Subject:      Re: Dometic Improvements Adding Fans
Comments: To: kevinm@RED.PRIMEXTECH.COM
In-Reply-To:  <3.0.2.32.19990427103121.007bfde0@red.prmx.com>
Content-Type: text/plain; charset="us-ascii"

At 10:31 4/27/99 -0700, Kevin Mikkelson wrote:
>
>I wanted to get the lists opinions, are there any unseen dangers (current
>draw?) in my wiring the stock fan in series with a second fan?

That gives you half-voltage to each fan (incidentally, "Muffin" is the
brand name of the original box-shaped electronic cooling fan -- now there
are probably twenty brands).  At half voltage if you're lucky or if the
motor is a brush-type DC motor the fans will run slower and quieter, and
give less output.  If you're *not* lucky and the motor is an electronic
one, the fan will sit still or rotate slowly backwards.  This obviously
does not provide the desired effect.  I'd suggest testing your fans with a
varying voltage and see for yourself what voltage they need to run.  If you
don't have access to a variable supply, get a pack of power diodes from
Radio Shack (p/n 276-1653, $2.29) and solder six or eight of them together
in series with the banded ends pointing the same way.  Hook the *non*
banded end of the array to your +12v and then connect the +lead of the fan
across one, then two, then three etc. diodes (letting it stop btw each
test).  When the fan quits running, go back one step and measure the
voltage across the fan.  Or figure that each diode is giving you a
half-volt drop, that errs a little on the side of caution.  Don't forget
that you won't always be running with a full battery; might go down to
eleven volts total, or maybe lower depending on where you get the fan
power.  The fans won't give you much voltage drop in the wiring, but the
reefer element will.

Yell if you need...
david
David Beierl - dbeierl@ibm.net