Judy, might I ask: what garage are you visiting? Are they suggesting that
you need an AC (usually stands for Air Conditioning) amplifier????
re the servo.... servo control for what?? you 79 diesel has a spinning cable
to run your odometer via the speed indicator I would think.
She is talking about that monster climate control unit/heater valve unit
used on her car and the W123...
As for the odometer... you need to check your cable first... at the
transmission to see it is loose. Otherwise, you might need to replace the
gears on the odometer.
On Jul 14, 12:08 pm, email@example.com (Guenter Scholz)
It's the servo for the climate control system. The amp drives the
servo which then makes the world go round. The servo is the highest
failure rate device in these cars. The sevo brings together
electric, vacuum and engine coolant all in one kludge design. MB
didn't even design it, they got it from Chrysler.
The servos fail for a variety of reasons, one of the main ones is the
bottom made of plastic where the hot coolant flows cracks and they
start leaking. I replaced my last one about 7 years ago. I got one
from a small company in Tennessee, Performance Analysis. They sold
servos that were made with a cast aluminum bottom half where the
coolant resides. This eliminates the cracking problem. I think it
was $600, but it was also warranted for 1 yr and then had a lifetime
guarantee where they would replace it for $100 if it failed. Now
mine has a very tiny weeping leak, but not enough to warrant
replacing. Overall I've been very satisfied, but eventually I expect
to have to use the $100 warranty.
There is also an aftermarket conversion kit that replaces the whole
servo/amp system with a microprocessor and solenoid valve
arrangement. TG on here has installed one and I'm sure can tell you
more. Last I heard he was very happy with it. Since you need both
a servo and amp, that could be the best way to go as it gets rid of
the whole crap system.
One thing I would definitely not do is buy either a used servo or an
amp from a salvage yard or similar, where you don't know what you're
getting. New ones are expensive, but trying to buy a used on is a
losing strategy. I've seen them on Ebay where they are being sold as
"pulled from a working car", etc., which is meaningless. It could be
10 years old and from a car that ran, but the climate control didn't
Regarding the odometer, is it just the odometer that is not working,
but the speedo is OK? If so, then it's the odometer itself. It can
be replaced or rebuilt. Pulling the instrument cluster is fairly
easy. I've seen places online that rebuild speedo's for you.
Good luck with the car.
you 79 diesel has a spinning cable
Interesting... you can convert it to a Manual Heat Control for far less.
The retrofit kit that replace that original servo is rediculously
expensive... Performance Product sells them for $1800!
The retrofit kit can be had here for reasonable price... to maintain
Still pricy but compared to some paid $600? Even rebuilt one cost as much as
There are some speedometer shops that sell repair kits - the little
gears that your car needs. Do an internet search for "Speedometer repair"
I own a '80 300SD - for 28 years - and replaced its cursed servo and
amplifier with a digital retrofit climate control. It's made and sold by
a Tucson AZ company. www.unwiredtools.com This system fits all M-B
models that used the old Chrysler servo/amplifier system; it comes with
a five year warranty. Best of all it works!
Motorsforum.com is a website by car enthusiasts for car enthusiasts. It is not affiliated with any of the car or spare part manufacturers or car dealers discussed here.
All logos and trade names are the property of their respective owners.