Excellent info. Thanks for the help. I will try your suggestions.

How many pulses/sec per mph in 4th gear?

__________________
1983 Mercedes-Benz 240D
Automatic, A/C, Power Sunroof, Power Right Side Mirror
231K Miles FOR SALE MAKE OFFER

1 pulse = 1 rotation. The rest of it is drive train math.

__________________
1984 300TD

Does the W126 use the same Tach Amplifier system?

__________________
Current cars:
2000 ML55 AMG, 174k miles
2003 C240 T-Modell, 202k miles
1995 S320, 207k Miles

Some did. You should find amps in the early W126 diesels from 1981 until sometime in the 1983/1984 timeframe. I'm not exactly sure when the switchover occurred, but I know of at least one 1983SD that did not use the amp.

It's easy to tell. If you have the "trash can" on the left front fender, and it's at least 2 inches tall, and it has six 2.5mm electrical contact pins that hang upside down inside the cover when it's unscrewed, you probably have an amp.

Attached Thumbnails

   

__________________
Bob
'82 300D Petrol B-G Metallic

Where is the tach amp on a 1878 300SD????

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

The location of the tach amp beats me. I want to see the 1878 300sd first. Is the engine under the seat? Did you buy the car new?

Herr Doktor, it should be in the same location as is the W126s', on the inner left front fender. It looks like this when unscrewed from the socket...

Attached Thumbnails

 

__________________
Bob
'82 300D Petrol B-G Metallic

You should be able to see it in this photo in the lower portion. It's a 1980, but it should be in the same position that the 1978's is.

__________________
'81 MB 300SD, '82 MB 300D Turbo (sold/RIP), '04 Lincoln Town Car Ultimate

Sooner or later every car falls apart, ours does it later!
-German Narrator in a MB Promotion Film about the then brand new W123.

Yes, thanks to all for the photos and information....

We always called that an 'adapter' so I thought the 'amp' was somwhere else...

How in the devil do your get it apart without detonating cord????

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

When we were kids, we would call any really old car an '18**' instead of a '19**' just for fun. Dad and I still do it...

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

Here's an 1885 Benz...

__________________
1984 300TD

Found a cool thing today....

I placed a 3/4" OD x 1/8" thick nylon washer on the top of the silicon potting and re-installed the tach amp cover.

No more bouncing tach.....at leat for the time being.

Who makes a new tach amp????

__________________
Did you just pass my 740 at 200 kmh in a 300SD?????

1978 300SD 'Phil' - 1,315,853 Miles And Counting - 1, 317,885 as of 12/27/2012 - 1,333,000 as of 05/10/2013, 1,337,850 as of July 15, 2013, 1,339,000 as of August 13, 2013



100,000 miles since June 2005 Overhaul - Sold January 25th, 2014 After 1,344,246 Miles & 20 Years of Ownership

Hi, i know it's been a while, but has anyone got the larger version of the schematic posted in the first post ?
it seems it's now gone and the smaller one is a bit difficult to read.

Attached Thumbnails

 

Copy and Paste the the original image into Paint.
Then you can use the Zoom In function under the View tab (enlarges 100%).
The enlarged view can be additonally enlarged if need be.

In Paint, you can also use the Resize function to enlarge the image the percentage you choose.

__________________
78 W116 300SD 'Desert Rose' new as of 01/26/2014
79 W116 300SD 'Stormcloud' RIP 04/11/2022