Yes, it's true. Thanks to the helpful advice of many list members, I've
just spent the last hour enjoying an icy cold breeze blowing out from the
dash vents of my '72 Lebaron. I managed to bypass the ATC servo (that is
missing from my car anyway) and make the system work. I intend this to be a
temporary fix, only until I can locate a working ATC servo for a reasonable
price. Once a suitable ATC servo is located I plan to restore the system to
it's original functionality.
Forgive me for not mentioning everyone by name, but at least half a dozen
listers were good enough to provide advice and technical information.
Special mention goes out to Norman (sshaddow%att.net) who was kind enough
to scan all 12 pages of the AutoTemp II section of his factory service
manual and e-mail them to me. Without this very valuable information from
Norman I wouldn't have been able to complete this project so quickly!
For those who have no recollection of my saga, I recently acquired a '72
Lebaron with non-functioning A/C and heat. The ATC servo in the engine
compartment is missing, and the heater hoses were connected together
resulting in constant heater core flow. NOT a good thing here in Arizona as
the temp is rising above 100* this time of year.
The solution:
First, I obtained a manual control heater valve. This is the part common to
most full-sized Chrysler products equipped with manually controlled heat
(or A/C and heat) from the late '60's through the mid '80's. Cost of this
part was under $20 at Checker/Kroger/PartsAmerica.com. The valve allowed me
to stop the flow of hot water through the heater core. This alone made an
amazing difference in the comfort level inside that car on Phoenix's first
100* day a couple of weeks ago! :^) Next, I purchased a "manual choke
control cable" at WalMart. $6 plus tax. I ran the choke cable from the
inside of the Lebaron, through the firewall (right next to all the existing
vacuum lines that run to the ATC servo when it's there) to the manual
control heater valve. Some minor fabrication and a couple of screws and I
had myself a nice, workable heater valve. Next January, when the temp falls
below 70* for that ten minutes around midnight, I'll be able to reach down
and turn on some heat (you know, for the sensitive lady folk...).
Next I sat down with an electrical schematic (kindly provided by Norman)
and decided what needed to be hotwired in order to make the compressor
clutch engage, and the fan motor blow. Master switch, passenger compartment
ambient sensor, compressor switch were all patched. The ambient sensor
under the hood appeared in good working order and didn't have to be
bypassed (this sensor cuts off the compressor circuit if the temp falls
below 32*). At this point I had a functioning system... compressor on, fan
blowing on low.
Finally, I had to get more airflow, so I jumpered the fan circuit at the
speed controller. Jumpering from "feed" to the "high" terminal produced the
results I required. Now I could turn the system on and off using the
dashboard push button control. The only remaining problem is to jumper the
vacuum lines to control the blend-air, outside air and discharge air
servos. Currently my airflow is split among the floor, dash and defroster
vents. Comfortable now, but when the heat climbs over 110* or 115* this
summer it won't be as comfortable. A few minutes with the vacuum schematic
and I should be able to accomplish what I need.
Oh yeah, one last thing... my A/C guy had to remove the ETR valve before
recharging the system. Apparently the solenoid was stuck closed. After
consulting the electrical schematic I've determined that there is a thermo
controlled compressor cutoff switch that works in conjunction with the ETR,
so removing the ETR won't have a dramatic impact on the system. Anyone who
wishes to offer an opposing viewpoint to this subject, please do so. I
always appreciate the advice of more experienced individuals. We also chose
to bypass the rear A/C lines rather than replacing the ruptured hose. This
had two advantages... first, the system used less Freon to recharge, also,
there's 20 or so feet less hose to possibly rupture again in the future.
His expert advice and labor cost arount $50. $30 for fittings and a new
hose. Freon came from a donor car, so there was no cost for that, other
than the labor to have it evacuated.
Total project cost is around $120. This would have been much less if my
system was holding pressure, but the ruptured rear air line created half
the cost. Still, a small price to pay for comfort! :^)
Once again, thanks to all who provided advice during the course of this
project.
DD
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