Neil:

It looks to me the internal fan will see +12V from either home or shore
battery depending on the position of the DPDT switch.

If the rear fan switch is closed (conected) you will not get 24 volt.
It will still get +12V from either the home or the shore battery.
But if it gets +12V form the shore battery (through the DPDT switch)
and the thermal switch is closed at the same time it will put both
batteries in paralle, meaning it shorts the +12V leads of the two
batteries. This is a problem. If one battery has a higher voltage than
the other there will be current flowing from one battery to another,
which is like charging the of a lower voltage. It may not cause
any damage to anything if the voltage difference between the two
batteries is very minimum. But if the difference is not very small
It would be like shorting a voltage of the difference, which could
easily burn the wires or the switches at the moment they are connected.

Batteries should never be connected in parallel.

David

--- neil N <musomuso@GMAIL.COM> wrote:

> Hi all.
>
> The diagram:
>
> http://web.mac.com/tubaneil/iWeb/Site%205/DometicWiring.html
>
> Fans work properly from both power sources. Internal is switched at
> DPDT, and rear is switched dependent on power from DPDT.
>
> IF thermal switch went "on" AND power still "on" from either source,
> will rear + internal fan see app. 24 volts if "rear fan switch closed?
> Or are they in series? (remains app 12V)
>
> Many thanks, if anyone can answer!
>
> Neil.
>
> --
> Please send me your Vanagon/Westfalia links!
> http://vanagonlinks.googlepages.com/home
>
> Neil Nicholson. 1981 Air Cooled Westfalia.
> http://web.mac.com/tubaneil
>

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