[Chrysler300] 1955 C-300 Power Seat Repair and Gearbox Lube

[Rich Barber <barber@xxxxxxxxx>]

I spent the afternoon getting the power seat in my 1955 C-300 to work.  
Before, it would just click, but not move.  I'm sharing my findings and 
procedure below, but have a question first.

Page 201 of the 1955 Chrysler service manual states:  "The vertical 
power unit shaft is equipped with a ball nut and should not be 
lubricated.  The horizontal power unit shaft is equipped with a friction 
nut that is packed with life-time grease requiring no further 
lubrication."    Additionally there is a gearbox on the horizontal power 
unit where a small worm gear drives and rotates the worm drive power 
unit shaft.  If that gearbox was also packed with "life-time grease", 
its life-time is over and the grease is gone, having leaked out and and 
accumulated on the exterior of the gearbox and assembly and attracted 50 
year's worth of dirt and dust bunnies..  Anyone have a recommendation 
for what kind of grease to pack that little gearbox with?

Findings and Procedure:

Inoperation was partially due to a buildup of crud on various rotating 
elements, especially the 3/4" (?) worm gears that position the links and 
torque rods.  With the assemblies removed and the motors direct fed from 
the battery, nothing would rotate until disassembled, cleaned and lubed.

Inoperation was also partially due to one of the two switches not 
feeding a ground in one position as it should. 

The ground cable was disconnected from the battery.

The front seat bottom can be removed by just lifting it up.  Pretty 
handy!  Looks like a plumber's and electrician's nightmare under there, 
but you don't have to understand the complex mechanical linkage to work 
on the system.

The six wires connected to the switch were tagged and removed.  This 
enabled checking the various switch positions for continuity.  One 
position was dead on the vertical switch, so the seat could not be moved 
down after being sent all the way up.  Jumpering a ground to the relay 
enabled reversing the motor.  It was possible to clean the worm drive 
power shaft of the vertical unit without removing the power unit by 
spraying with WD-40 and ragging it off.  So only repair of the switch 
was required

Both switch positions worked ok for the vertical power unit and produced 
relay clicking at the motor but no rotation.

The steel and aluminum surround at the driver's side of the seat base 
was removed by removing four small sheet metal screws holding it to the 
seat frame.  This enabled  access to the three screws holding the switch 
assembly to the surround..

The surround was cleaned and the aluminum polished.  The steel part of 
the surround needed repainting with black enamel, that for another day. 

The switches are serviceable, sort of.  Each of the two switches is held 
in the chrome pot metal housing by two spring steel clips.  I ended up 
breaking the clips to get the bad switch out of the housing.  Once out 
and cleaned, it became apparent the black plastic switch body was held 
together with small wire clips that were sort of like big square 
U-shaped staples.  These clips were easy enough to remove and enabled 
the inside mechanism and contacts to be accessed.  One of the sets of 
contact points had enough erosion and corrosion to prevent electrical 
contact.  Not having any contact cleaner, I just polished all the points 
with a little brass detailing brush and reassembled the switch using the 
two wire clips.  Much like filing a set of ignition points.

Not having replacements for the broken spring steel clips, I just jammed 
a couple of steel brads into the spaces where the clips would have 
gone.  This seemed to do a good job of securing the switch in the 
housing.  Time will tell how long this crude fix lasts.

I removed the vertical power unit after first removing two small snap 
rings from the mounting pins.  This task required a snap-ring tool with 
tiny points.  The relay box was removed after tagging the wires.  The 
relay functions checked out ok.  The wires from the switch provide 
grounds to the relay and cause high-amp hot current to flow to the 
armature and one or another of the fields of the motor.  There are three 
wires coming from each motor.  The two smaller wires are fields, one for 
each direction.  The larger wire is the armature connection.  To test 
the motor, I bolted one field wire to the armature wire and connected 
these two wires to the Negative (Hot) side of my 6-Volt battery.  Then 
connecting the Positive (ground) side of the battery to the body of the 
motor.  After completely removing the motor from the gearbox, The motor 
started and ran fine in both directions.  (Whew!--what a relief--don't 
have to go shopping for a motor.).  After cleaning the worm drive power 
rod and the gearbox, they were reassembled to the motor and the system 
worked fine in both directions with direct power from the battery.  
There was a large rubber flex coupling between the end of the motor 
shaft and the small worm gear driving the power rod.  I think some of 
the accumulated crud was surrounding the coupling and preventing rotation .

Reassembly went fine.  The seat can be levered as needed to allow the 
power unit to be slipped over the two mounting pins.  I WD-40'd the 
connection points on the linkage and torque levers.

Reconnected the battery ground cable and everything worked fine.  The 
motors ran smoothly and quietly.  Cleaned and buffed the leather seat 
base while it was out.  Also vacuumed the carpet under the seat.

Now that the power seat works, I can install the seat belts I bought 
last year.  I have sure felt naked without them and 
she-who-must-be-obeyed will not ride in the car without them.  One old 
report on the 1955  Chrysler 300 said the car cornered better than the 
driver, what with the slick leather seats.  Not so bad when you have a 
steering wheel to hang on to, but there is no panic bar for the 
passenger to grab.
I hope this may be helpful to anyone with inoperative power seats.  The 
bottom line is they are a complex electro-mechanical system, but can be 
services with simple tools and unskilled labor.  I assume they are 
pretty much the same in later years.  Consultations available and 
criticisms welcomed.

C-300'ly,
Rich Barber
Brentwood 94513




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