I am looking at a 78 300D. The issue is its my first diesel and I have
been told by the owner that the climate control servo needs to be
replaced. They have set the servo so the heater works and purged the
system of freon. Here is my issue, after talking to a couple of shops
they are saying they would need to upgrade the AC at the price of $900
which would remove the climate control servo. Is there a way around
this and can you still buy the old style freon? Other than that this
car is in great shape with less than 150K on it.
Thanks in advance.
YES. This servo / amplifier system is awful and ought to be junked.
Go to www.unwiredtools.com and look at their digital retrofit kit for
this application. Their kit replaces the servo and the amplifier, both
of the troublesome elements of the OEM climate control system.
I installed one in my '80 300SD and am pleased with its performance.
Hopefully there are no other "modifications" to the climate control
system of the car you have in mind.
Are you satisfied with the acceleration of the 300D? If not try a 300D
Turbo or a 300SD which uses the same turbo motor.
I've been wondering about this setup. What happens when the heat is
off? I mean, is the electric water pump also turned off, or does it
push on the closed valve, or does the coolant get shunted somehow? When
I rerouted my hoses to bypass the ACC, the only thing I could imagine is
that the secondary water pump keeps pumping but that the servo shunts
coolant flow. Is that the case?
Last year I had the R-12 Freon "topped up" in my 300SD's and was told
that the R-12's cost, though high was not too much higher than the R134a
whose price has risen a lot. Price it both ways: R-12 and conversion to
I had mine converted to R134A about 10 years ago, with original hoses
and no leakage problems to date. However, I did the conversion based
on the R12 becoming increasingly high price and forecast to disappear.
With the way things are now, I'd keep it R12.
Regarding the climate control system, another alternative to consider
is replacing the servo with one from Performance Analysis, in TN.
They rebuild them and use a lower case made of aluminum, which
eliminates one of the main failure modes. Cost is $600, I think, and
after the 1 yr warranty, they will fix it for life for $100. As
pointed out, this assumes they haven't screwed up and modified the
whole climate control system in your car.
Also, I don't think I'd be too excited about this non-turbo diesel.
There are 300SD's available from that era that have much more HP,
making them more drivable, plus you get a bigger, nicer car for not
much more money.
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