Re: [A/S] '64 Globetrotter 19' electricals

["Christopher H. Dow" <dow@xxxxxxxxxx>]

> Chris,
>  Sounds like you have a mellofahess on your hands. :-(

Yeah, it's almost like Joe Lucas got into the trailer from the Land
Rover while I was towing it :-).

> First thing, get a copy of Barre's "Managing 12 Volts" and Livingston's
> "RV Maintenance and Repair". You need them both!

Thanks for the recomendation.  Leslie had already ordered the Livingston
book, and I just ordered "Managing 12 Volts".

> I think you're confusing "Inverter" and "Converter". The former is
> somewhat unusual in a travel trailer; it makes 120VAC from the 12VDC
> battery(s). The latter supplies 12 volt power when connected to shore
> power and charges the battery. Some of them supply 12VAC for the lights
> and a seperate 12VDC circuit for battery charging, others have only the
> 12VDC output.

I realize now that I wasn't being very clear.  The inverter in the
cabinet in the back of the trailer is not mounted. It has alligator
clips (not like the ones on a battery charger as I previously stated)
going in, and two 110VAC outlets going out.  One of those outlets has a
2-prong to 3-prong converter in it.  My hypothesis is that the PO used
this to create his own "shore" hookup while he was boondocking by
hooking the inverter up to the battery, and plugging the shore hookup
into the inverter.  I think this was his fix for the trailer not working
on battery power.

The gizmo on the floor--what I called a transformer--is made by GE.  The
Fluke DMM I've borrowed tells me it has 12VDC and 19VDC outputs.  This
corresponds to the wiring diagram in the manual, which I have recreated
and placed at http://www.thelen.org/airstream/ASWiring.pdf (perhaps it
can be of use to others).

> The fridge PROBABLY only works on 120VAC, not 12 volts (AC or DC). It's
> uncommon for TT fridges to have a 12VDC heater, but very common for MH
> fridges to be so configured. The fact that your fridge won't work when
> switched to "Electric" probably has nothing to do with your botched up
> 12-volt system.

At some point in the past, the refridgerater was replaced with a
Dometic, which is capable of being connected to 12V, 110VAC (according
to the manual and the information on the back of the unit), or running
on gas.  The wires going to it are connected to the posts on the unit
marked for 110VAC.   I wonder if those wires originally went to the
outlet (near the fridge) which does not work.

> If you have multiple charging sources such as solar, converter, and tow
> vehicle, it's usual to simply have them all connected together and to
> the battery. The highest-voltage source will be the one actually
> charging the battery(s). 

OK.  That's what I'll do then.

> I don't know what you have in your tow vehicle, but the most common setup is to
> have an "isolator" between the tow vehicle battery and the "charge" line going to
> the trailer connector.  Some folks use a diode isolator, others use a relay; I
> prefer the latter myself.

I opted for a diode isoloator.  I'm interested in why you like relays
better.  I originally wanted a relay, but decided on a diode-based
system which only charges the trailer battery when the tow vehicle
battery is in good shape.

> If you want to isolate the 12 volt problems most quickly and safely,
> here's what I'd do:
> 
8<

Thank you for your good advice on this.  Here's what I've done so far
(using a borrowed Fluke DMM instead of a light bulb):

I removed the "black box" and found the wire which I had connected to
the battery was connected to the place where the 12VAC output from the
converter came in to the City/Battery switch for lights.  This may
explain why it dead-shorted, and may not.  Anyway, I know how it's
hooked up now, and know that it's wrong.  This was after recreating the
wiring diagram, which got me VERY familiar with the way it *should* be.  

Next, I tested to see where the 12VDC was going inside the box.  I found
that the switch for lights had 12VDC going into the top of it, but
coming out nowhere--even when the switch was set to 
"Battery  Power" (clue number one!).  I then switched to "Cityy Power",
hooked up shore power, and found that when the switch was in the "City
Power" position, the bottom connector had 12VDC and the middle connector
had 12VDC as well.  I conclude from this that at least my switch for
lights has a faulty contact when in the "Battery Power" position.

> Leaving the converter ("inverter") output disconnected from the battery
> and everything else, connect your shore power cord. Get your 120VAC
> circuits working. If you have no "dual" light fixtures (with both 120
> volt and 12 volt bulbs), you'll have only receptacles to worry about.
> One will be behind the fridge and may be the cause of its not working on
> "electric". One will have the converter plugged into it, or there will
> be a pigtail from the 120VAC circuitry that is hard-wired to the
> converter.

Yes, there is a pigtail from the 120VAC circuitry that is hard-wired
into the converter. I still need to work over on the 'fridge side to see
what's up there.

This trailer has only 12V lights.  My guess (still haven't tested the
sockets) is that they are 12VAC when on shore power, and 12VDC when
battery power is correctly applied.  

> Then, check out your converter to make sure it's wired correctly and is
> working. Reconnect it to the battery and trailer circuits. If it's the
> kind that feeds 12VAC to the lights, etc. and switches to battery power
> when disconnected from the 120VAC, you'll need to connect it
> accordingly. Better yet, toss it and get a modern converter/battery
> charger such as the InteliPower with Charge Wizard.

I have come up with a new schematic for what I want.  It's at
http://www.thelen.org/ASWiring-mod.pdf 

It shows a charger, tow vehicle, and solar setup connected to the
battery as well as an inverter.  Since most everything is 12V, that
gives me all I need for hookup, tow charging, and solar charging, and
leaves me the outlets when I'm boondocking.  I don't expect to need them
much, but it would be nice to have them occasionally.  I think that that
will make it so that I don't even have a switch to thow when hooking up.

> Good luck!!

Thanks!

> "Christopher H. Dow" wrote:
8<
> > First, a description of the electrics as described in the manual:  It
> > states that ours is a univolt trailer.  It further states that there are
> > two 12V systems, and one 110V system.  There is a 12VDC system for
> > lights, and a 12VAC system for the 'fridge and the pump.

Actually, what I wrote here was wrong.  There are two outputs from the
GE transformer:  12VDC and 19VDC.

C