This is a too-longish report on what I have learned recently about horns on
6-Volt 1955 Chryslers. Much is from the Parts Manual and some is from
observation and experimentation. The Parts Manual says this information is
only for non-CA built cars, but provides no information on CA-built cars.
Were some 1955 Chryslers made here in sunny CA?
Production of Windsors, New Yorkers and Imperials started with two Trumpet
Horns, each starting downward from the housing, then through a right-angle
bend towards the center of the car and ending in a flared horizontal
opening. The passenger's side horn continued as a Trumpet Horn throughout
the year, was the longest horn and was the low note horn.
During the production year, the driver's side trumpet horn was changed to a
more compact horn called a "Sea Shell" by Chrysler. The Parts Manual gives
the VIN's at horn changeover for the Windsors, New Yorkers and Imperials as
51982, 31836 and 7837, respectively.
The Parts manual does not address horns on 1955 300's, but early 1955 300's
have two trumpet horns and 1955 300's produced later in the year have one
Sea Shell on the left and one Trumpet Horn on the right. It would seem
Chrysler changed all the 6-Volt cars' driver's side horns over at about the
same time. Chrysler horns carry part numbers that are different from De
Sotos and other 1955 Chrysler products.
Imperials standard equipment may have included two Sea Shell type horns on
the driver's side along with the standard passenger's side Trumpet Horn.
There are two different Sea Shell Horn tones. If there are two Sea Shells
installed, the upper horn has the lowest note and the lowest horn has the
highest note (go figure). It is unclear which Sea Shell was standard if
there was only one Sea Shell installed.
It would appear that the second Sea Shell may have been an option on some or
all of the Chrysler models. Our judges deduct concours points if there are
more than two horns total on 300's. From that, it would appear that it has
been confirmed that the three-horn option was not available from the factory
on 1955 300's.
1955 Chrysler horn relays are supposed to be wired so that the hot side of
the coil in the horn relay only receives power if the ignition switch is on.
A wire runs from the ignition switch to terminal (I) on the horn relay. A
second wire is attached to the same terminal (I) and proceeds on to the
coil. 1955 Chrysler horns should not be able to honk unless the ignition
key is on. (My 1999 Jeep Wrangler and 2005 Durango DO honk without the key)
But who ever tries the horn in the garage? Try it and let me know if this
is not so on your 1955 6-Volt Chrysler.
My early C-300 actually has a rather damaged three-lug horn relay that is
wired so that it can honk at any time. Only the coil is connected to the
ignition switch. I feel this was a repair and modification and will rewire
it and install a replacement four-terminal horn relay.
The ground side for the coil (S) in the horn relay is provided when the horn
ring is pressed (or when the connecting wire shorts out in the steering
column--usually at an inopportune time).
Power for the horns comes from a heavy #12 green wire running the short
distance from the big lug on the starter relay to horn relay terminal (B),
through the horn relay contacts to terminal (H) if the ignition key is on
and the horn ring is depressed, through another green #12 wire to the horn
on the driver's side. Another green #12 wire is attached to the first horn
and runs across the radiator support to the passenger's side horn. There is
no circuit breaker in this circuit, so it is especially worth inspecting
periodically to assure its wiring is properly supported and not rubbing
through its insulation.
Non-operating horns might be returned to service if the magnet coil and
resistor are intact and if the diaphragm and housing system has not corroded
past the point of no return. I got mine working again with only minor
effort, but I'm not sure what the secret was. The horns are easily
accessible and easier to work on if they are removed. Tape and secure the
disconnected hot connection if you don't plan to immediately return the horn
to the car. You don't want a dead short if the horn circuit is actuated.
Horn noise is generated by a vibrating diaphragm in between the upper and
lower housing and the diaphragm is riveted in place between the housings.
The "hemi" horn cap that has AUTO-LITE stamped on it can be removed by
prying open the two short sections of the cap that wrap around the bottom
housing. I have only been inside one Trumpet Horn, but assume the Sea
Shells are similar (try saying that fast).
My driver's side Trumpet Horn was not working, although it would click. I
tried adjusting the small lock-nutted screw, but to no avail.
I tried the highly recommended low-tech fix of trying to loosen up a
possibly corroded-in-place diaphragm by loading up both sides of the
diaphragm with WD-40, Deep Creep and Kroil. By itself, this didn't work,
either, but I think it aided the final fix. I also gave the horn a shot of
12 Volts. That just made the mouse milk smoke as the coil got hot quick.
A fellow member sent me some pages of tech tips on similar GM horns that
suggested drilling out the rivets to access and clean the rusty diaphragm.
I was ready to try that, but decided to clean the electrical contacts in the
horn with an ignition file and try a few adjustments and measurements first.
There is an apparent resistor in the circuit between the horn vibrator coil
and its ground. An Ohmeter confirmed the resistor was intact with under one
Ohm resistance. Likewise, it was possible to measure the resistance of the
coil as the coil wire ends are obvious and accessible. The coil resistance
was also under one Ohm. The horn vibrator coil is made from fairly heavy
wire as it may carry 15 Amps. It and its connections look pretty rugged.
I removed the small adjusting screw and the larger nut on the threaded post
that is attached to the diaphragm. I'm not sure there are points in between
the leaf springs of the horn, but after removing the adjusting screw and the
larger assembly nut, it was possible to open up the leaves enough to get the
ignition file in there and I filed away at whatever was in there. It didn't
really look too corroded or burnt in there. Horns work by a high-frequency
making and breaking of the circuit providing power to the coil, so there
must be points in there somewhere.
After the large nut was removed it was also possible to adjust the gap
between the heavy steel disc and its mating housing by rotating the steel
disc on its threaded post. This apparently adjusts the volume by adjusting
the allowable travel of the diaphragm. I set it about .040", ran the
adjusting screw in about half way and, wonder-of-wonders, the horn sorta
started working. Fiddling with the adjusting screw and the rotating disc
tuned it up and resulted in the emanation of a rather pleasant, loud
K-Whopper grade tone.
I wire brushed the two bolts that secure the horn mounting bracket to the
horn. These have one end riveted into the housings and they were rather
dirty, painted and perhaps providing a poor ground connection. I also wire
brushed the contact areas near where the single bolt fastens the horn
support to the radiator support to assure a good ground there.
While I have the horn out, I'll bead blast and paint its exterior tomorrow.
In retrospect, the adjustments were probably the key factor in the return to
service but the diaphragm housings create a natural place for condensation
to collect and corrode the steel diaphragm and this could affect the
diaphragm to the point of locking it or severely limiting its action. The
WD-40, Deep Creep and Kroil can't hurt anything and may have broken down the
housing to diaphragm corrosion enough to enable the system to function. The
electrical measurements, filing and adjustments could probably be done
without removing the horn if the cap is removed.
Preventive maintenance might involve giving the upper chambers of the horns
a good shot of WD-40 once a year. There is a large, rectangular and
readily-accessible hole in the housing underneath the cap to apply this
Water Displacer 40.
I can't wait to try out the repaired and tuned dual Trumpet Horns on the
next airhead that is so busy on their cell phone and subwoofers that they
haven't noticed the light changed.
At future meets, I'll try to get comparative tones of the several types of
1955 Chrysler horn configurations. Concours judges may want to begin
checking to make sure both horns work if they are not already doing so. A
single horn tone would be a dead give-away.
Thanks to the experts and fellow 1955 C-300 aficionados that provided
feedback to enable me to prepare this report and return my horn to service.
Input on various NY's and Imps was also valuable. Further input to correct
or enhance this report is welcomed. I have a few pictures of the exposed
horn assembly. If they would be helpful to anyone, let me know and I'll send
them.
Fully doubly horny once again and C-300'ly,
Rich Barber
Brentwood, CA
1955 C-300
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