Electrical System
Like just about everything else in my
Overlander, both the 120 vac & 12 vdc electrical systems were completely
original with the exception of a new outlet in the kitchen when we first
started camping. Although I have no
formal training in either electricity or electronics, I have hobbied with both
since I was a little kid, and am quite comfortable working with both. You may not be.
But
if you are, and are looking for a little insight into what makes a vintage
Airstream tick electrically, there are a few observations worth sharing. Although I have tried to keep the “glaze
factor” down, my tendency is to drift into the minutia, so feel free to email
me for clarification if I should lose you in useless detail. 
The Wiring
Solid
aluminum wiring was all the rage in the late sixties because it was cheaper
& lighter than copper. What aluminum
wiring lacked in conductivity as compared to copper could easily be made up in
increasing the wire’s diameter. When
sized & installed by a properly trained individual, it works great. Unfortunately, if the correct connectors are
not used, problems can occur.
In
a nutshell, different metals expand & contract at different rates when the
temperature changes. If a wire is
connected to terminals made of metal with a different expansion/contraction
rate, after several temperature changes, the connection will loosen up. After that happens, arcing at the connection
can occur. Either the heat from the
arcing or the arc itself can prove to be a fire hazard.
It
is my understanding that a flood of improperly installed aluminum wiring forced
National Electrical Code changes banning the use of solid aluminum wire in residential applications. Stranded
aluminum wire, commonly used in high current applications, is still
allowed. Seems like I heard that solid
aluminum wire is still used in mobile homes.
Both
my Airstream, and my house use aluminum wiring for 120 vac circuits. My Airstream was in a great shape. My house, however, had several instances of
improper connections. If your Airstream has
aluminum wire, it would behoove you to check each outlet & breaker to make
sure it is rated for aluminum wire and that the wiring’s screws are tight. Most home improvement stores sell special
outlets & switches rated “Cu/Al” or “CO/AL” (copper/aluminum) wire. For what its worth, I have heard that the
terminals are made of zinc.
Copper
wire is used for the 12 volt circuits in my Overlander. I have a feeling the Factory would have used
aluminum if they could, but did not for two reasons. 12 volt circuits have to be able to carry a
lot of current since the voltage is so low.
10 gauge wire is the largest solid wire gauge I have seen available, and
that may not be big enough. But aluminum
wire was probably not used because its lower conductivity would result in an
intolerable voltage drop (dim lights, slow motors).
Update: My Airstream was built at the Ohio plant. I found out the other day that a friend of mine’s two ’67 Airstreams built at the California are wired differently. In both of his Airstreams, the copper wire carries 120 vac, and aluminum wire carries 12 vdc. For the reason outlined in the paragraph above, I think a boo boo occurred at the factory. But I did want to pass the info on.
The Univolt
I
like the Univolt. But I also appear to
like doing things the hard way like lighting pilot lights & winding
clocks. Sure, the modern day power
converters do a fine job of powering 12 volt circuits & keeping the battery
properly charged. But I enjoy having a
“say” as to when & how much my battery is charged. Everything nowadays is computerized to do its
job. Computerized control is great…while
it is working. New boards always seem to
cost at least $100 if they are still
available. Now that you realize I am
eccentric and cheap, 
here are a few observations on the Univolt:
Univolts
do not regulate the voltage they deliver. They were designed to output one single
voltage with as much current as available. A Univolt is amazingly simple: A big
transformer to step down the voltage, diodes to convert AC to DC, and
capacitors to tune the circuit.
If
you were to study power supply theory, you would find the Univolt’s circuit
listed as a ferro-resonant transformer.
I believe this particular design was chosen because its output terminals
will continue to deliver full current, with no adverse affect to the
transformer, even if they are shorted
together. 
While I have a schematic for those that are
truly interested, ferro-resonant basically means there is a capacitor hung off
a tap on the output windings to tune the circuit.
Some
people appear to think that a battery must be present for the circuit to be
properly tuned. This is incorrect. The battery serves to filter, and smooth the
Univolt’s output, but is not required
for operation. However, your 12 volt
lights will be dim, and your radio will have a lot of static in the absence of
filtering & smoothing. During the
refurb, and now in the winter, I keep a bank of old electrolytic capacitors out
of my toy box wired up to act as a “battery simulator”. The capacitors do all the filtering &
smoothing, and allow me to keep the battery in plain view in my Shop so I don’t
forget to check it every so often.
Speaking of battery charging
My
'67 owner's manual says that
the Univolt has a 100% shut off and that it is impossible to overcharge the
battery. I will give Airstream the benefit of the doubt, and assume that
some Univolts had a circuit breaker which would trip to effect "100%
shutoff". A Univolt has no "smarts" to it. It could care less if your battery is
boiling, simmering, or even there. It's
job is to supply roughly 13.5 vdc with as much current as it can muster. I put it that way because, the voltage will
drop as the load on the Univolt increases.
If you are actively camping and have a bunch of lights & fan motors
going, the voltage difference between the battery & the Univolt will be
small. In fact, the battery may even help the Univolt out if you have A LOT of
stuff on.
A
battery is charged by applying a DC voltage to the battery that is higher than
the voltage the battery currently has. The higher the voltage difference, the
greater the charge rate will be. I believe a fully charged battery will read
12.9 vdc on a volt meter.
Charging
a battery is an electro-chemical reaction. As the battery charges, tiny bubbles
of hydrogen gas & water vapor form on the plates, and eventually bubble
off. These bubbles eventually escape from even sealed batteries. The higher the
charge voltage, the more bubbles that are formed. It is this bubbling that is
commonly referred to as boiling although it does not occur the same way as
water boiling in a tea kettle.
But,
with no lights or anything but the Univolt on, the battery will be subjected to
the maximum voltage the Univolt can deliver. It will attempt to charge. After a
while, the water will bubble off.
My
Univolt is conveniently located under the bathroom sink. While reinstalling it during the refurb, I
took the opportunity install a simple, external ON/OFF switch. When camping on shore power, I leave the
Univolt off unless an electric motor is running, or a lot of lights are on. Between this switch, and the original analog
battery minder, I have yet to boil a battery.
Power Quality
Just
because a campground has a 30 amp receptacle for you to plug into does not
necessarily mean you will get power your Airstream is happy with. A lot of trailers at the campground all
running their air conditioners, may affect the line voltage. Ideally, you would like to measure 120 vac on
your voltmeter once you plug up. After
letting your air conditioner run for half a minute or so, the voltage will
probably drop a volt or two. As long as
the voltage stays at or above 115 vac, you’re in
Also,
if you have to use an extension cord to plug your Airstream into shore power,
make sure its wiring gauge is 10
gauge or lower. Lower gauge means
thicker wire. The wiring gauge should be
stamped on the outer insulation. If it is
not, it is a cheap extension cable & should not be trusted. I only point this out because I once saw a
vendor selling an extension cord with 30 amp fittings, but the wire gauge was
12 gauge, which is only rated for 20 amps.
Using the wrong gauge can result in an unwelcome voltage drop.
Light Bulbs
My '67 Overlander requires two certain light bulbs, an 1141F, and
an 1176, which proved impossible to find locally. All the big, on-line
companies sold one, but not the other.
I found a "Mom & Pop" place in I ordered a total of 40 light bulbs which
were UPSed to my door for a grand total of $10.36.
Their website does not list prices, but they do have a 1-800
number. Rosemary was quite helpful.
BTW, the 1141F, a frosted version of the common 1141, is now
designated as 1141IF. The version sold to me by AMT Electrical looks different
than I was expecting, but works just fine in my Overlander.
12 volt Circuit Breakers
In 1967, Airstream used three, 12 volt, 20 amp, self-resetting
circuit breakers to limit current flowing through the 12 volt DC circuits. Additionally, there is one, 25 amp breaker in
the belly which keeps an eye on the charge wire’s current.
Coincidental with replacing a bad light switch, I had one of these
breakers bite the dust. Kinda cool how simple the
breakers are. The autopsy showed the device has nothing more than a bimetallic
strip with [apparently] a certain amount of electrical resistance. When too
much current is drawn, the strip pops the circuit open. When cool, it closes.
In my case, the contacts had fused, and melted away from the
strip. The point source heating around the damaged contacts made the breaker
work in an interesting way.
Luckily, with minor modification, the breakers being sold nowadays
are physically quite similar to what I had. At $3 a pop, I replaced all three
breakers.
Light Switches
Everything
went fine on our first couple of camping trips.
But then the kitchen sink light switch failed in the every-bulb-ON
position. Although I could see the
original switch had been made by Leviton, they now no longer make it. Much time was spent on the Internet, and at
local lighting vendors to no avail.
Although 3-position switches are still being made, none could be found
that had the shaft length needed for my light fixture. So, at over $15/switch plus S&H, I ordered
two from an Airstream dealer.
The
previous owner must have used the kitchen sink light a lot because the
insulation on the light bulb sockets’ wires was dark & hardened. I was able to find new socket center contact
wiring at a local auto parts house.
A
couple more camping trips later, the second switch was installed in the bedroom
fixture when that switch failed.
Interestingly, the sockets’ wires did not need replacing in this
fixture.
A
couple more trips later…
Since
I could see where this was going, I broke down ordered three switches, and
replaced the rest before they could fail.
The bath fixture, judging by the wire caps used, appeared to have been
replaced before. But, to be on the safe
side, it was also replaced. My motto is
now, “Replace your light switches every 38 years whether you need to or not…” 