Bypassing a bad ATCII heater servo unit - options
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Bypassing a bad ATCII heater servo unit - options



suggested that as a temporary
> solution to my leaking servo I take the 2 water hoses
> coming from the motor and splice them together.Is the
> heater the only thing which will be affected and will it
> not harm anything?

This is correct.  If you don't have a service manual, you
have just reached the point where one will pay foritself
with drawings and explanations.  This portion of your car
is quite mysterious until you see a picture of how it
works.  After this, you'll have a working knowledge of
every heater in every car that I can think of, excepting
the late '50s units that came with a gas heater and are
rare and noteworthy for that reason.

To explain:

Your block has 2 hoses for the heater that go from the
engine to the firewall, through the Auto Temp Control II
Servo, which I call the ATCII.

One goes out to the heater from the engine block and one
returns the water from the heater into the engine block. 
This is common to almost all cars.  The heater is a
miniature radiator that the incoming air gets blown across
to yeild hot air in your car's cabin if hot water is
flowing through it.  Your heater does not work until your
engine heats the water in the engine block, and this
explains why a heater set to "hot" on a cold engine will
only come up to being hot as slowly as the engine warms the
water flowing through it.

The heater water also goes through a valve.  -Most cars,
that's a manual slider bar on the dash that you slide or
twist to open, with the strength of your hand moving the
valve, just like a home sink faucet.

The Autotemp is electronic/vacuum operated and is designed
with a thermostat so that you set the desired temperature
and the unit keeps that temperature, actuating the A/C or
heater as needed.  One could theoretically drive from Saudi
Arabian desert to Siberia without touching any buttons and
keep 68 degrees or whatever inside the car at all times
that the windows/doors were shut and the motor running.

If you decisde to bypass your Auto temp system, you have 4
options.  

1.  Bypass the ATCII unit only, but reconnect the hoses. 
You'll have 100% hot air all the time because the hot water
from the block can not be turned off as it goes through
your heater.

2.  Bypass the ATCII and return the hotwater "out" to the
hotwater "in" on the block before it gets to the ATCII
servo.  No hot water flows in the heater ever, and you have
no heater.  This is viable where I live in California.

3.  Bypass the ATCII and replace it with a manual slider
switch like regular cars have.  A hack (like me) could put
it where the ATCII servo is under the hood, neccessitiating
that the hood be opened to adjust the heat.  Kerry
Pinkerton did the slightly tougher, but more elegant method
of using a standard early '70's "Chrysler car" (newport?
new yorker?) manual heater valve and mounting it to his
dash in place of the ATCII control wheel.  I seem to
remember that the plates were the same cutout size and fit
right in, but you'll have to reread Kerry's description to
verify that.

4.  Pay for a new aluminum bodied ATCII unit.  Most seem to
 agree that junkyard ATCII units are destined to fail, so
probably a waste of energy, that.


Dive into this.  There's nothing that will bite.  Make
certain that your hose connections are tight.  If a hose
pops off, all of your radiator coolant will exit that hose,
making lots of steam and possibly hurting your engine if
you run it when there is no more coolant and the engine
overheats, but it's tough to do this unless you are really
inattentive to getting your hose clamps tight.  This
project is a good point at which to replace your radiator
hoses, too, if you have not done them in recent memory. 
They're cheap and a real bummer if they pop due to age.

Please write back with any more questions - we are always
happy to feild them.



=====
Kenyon Wills
6o LeBaron - America's Most Carefully Built Car 
73 LeBaron - Long Low & Luxurious

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