I am hoping someone can answer a little question for me.
I have a w116 chassis 300sd, the tach worked very rarely, so
I found the little round screw-off thingy in the engine compartment
and un plugged the top portion, cleaned off the pins with 1500 grit
sandpaper, put dielectric grease in the female side of the connector
and now have a tach 80% of the time. (I think I need to repeat cleaning)
My girlfriend has a w123 chassis 300d, and when I unscrew her
round thingy in the engine compartment, there is no top part under the
cover! I only see the female connectors, no plug in part at all.
(she has never had a working tach in the eight months she has
owned the car)
Is she missing part, or did they change the way things were done
in between the two cars?
what do you call that?
Thanks for any help
Depending on the year of your girlfriends car, the fix for the tach can
be as simple as a blown fuse behind the glovebox. I have a 1984 300D Turbo
with CA Emission Package. If you remove the 2 piece clips that hold the
glove box in place, about 8 of them, with a small screw driver blade. Then
pry the glove box light out of the way. Remove the glovebox "Box", and that
will expose a few relays and black boxes. If you look all the way to the
right, you will see a small box with a 10 amp spade type plug in fuse on it.
Chances are good that this fuse is blown or maybe just "crusty". BEFORE you
button up the "Box", check it out. If that fixes it, button it up and enjoy.
If that is not the problem or the car is of a different build date,
repost and maybe we can supply you with a different fix...
As for your Tach, I have read that you can put a filter from a cigarette to
help "shim" downward pressure on the plug. This gives you a tight fit and
eliminates an intermittent connection.
Or it could be the sender...
I call this a "tach amp" and you need two of them.
I messed around with mine for years cleaning it, fixing
it, finally I bought a new one. Save yourself the hassle,
get a new one. They always work and at some point you
do get sick of fixing them and staring at a dead tach
I know in the past I've recomeneded dialectric grease on
tach amps. That was a mistake; in retrospect it never
did any good, in fact possibly the opposite. It is
an insulator after all.
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