[W126 Coupe] 1985 SEC clock

[Andrew Seidel]

Group,
Sorry I've not been in touch recently; quit job, moved to Colorado, and been fighting to get my e-mails to post to the list.

I just did the clock repair on my '85 Lorinser:

Parts needed:
QTY 2: 100uF electrolytic capacitors,  with axial leads of 5mm pitch, voltage rating of at least 24V 
( e.g. digikey.com P/N 493-1936 )

Procedure:
-remove instrument cluster, unscrew clock/tach module (need to remove the speedometer as they share a mounting screw)
-cover faceplate with lint-free cloth backed by lots of cushion, flip over and desolder the clock's GND pin from the brass ring
-remove screws holding tach faceplate and also the screws going into the plastic pegs of the clock assembly
-gently separate backing plate and turn to one side, exposing the capacitors (and a neoprene shim that needs to be pulled out of the way)
-desolder the now-exposed old capacitors 
-solder on new capacitors in correct orientation (polarity is well marked on the circuit board), clip excess lead length
-test with fused +12V and GND connections and look for movement (as much quieter than e.g. W123 clock)
-re-assemble the face and backing plates with the mounting screws
-re-solder the ground pin to the brass ring
-screw the module back in to the instrument cluster and re-install the cluster

Tips:
-be careful not to over-stretch the wires feeding power to the tach when the backing plate is opened out
-be careful during desoldering as the faceplate/tach/needles will be floating around without their moorings 
-for cap removal, recommend combo of brief heat from the soldering iron while pulling with needle nose pliers, then clean with copper braid
-use light machine oil, if anything, to oil the gears
-use *low*-pressure air, if anything, to clean
-clock's GND connection is through a brass ring that is simply punch-mounted to the backing plate
  --inspect the ring's connection is still good and be careful not to pop it out by tightening the screws after the GND pin has been soldered in place
  --tack solder the ring to the backing plate if it needs repair
  --clean the backing plate of oil, etc. where it makes GND connection with the rest of the cluster (through the screw shared with the speedo)
-use good soldering practices such as not applying heat too long, cleaning off excess flux
-the old parts will likely contain lead, so wash hands and dispose of the parts and used braid properly

Hope this helps,
 
Andrew Seidel
1986 560SEC
1985 500SEC
1983 300D Turbo




       
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