Tach signal ? - Page 2 - PeachParts Mercedes-Benz Forum

NC Benz · #16 07-15-2008, 08:54 AM

Thanks Too Many!!! I have been looking for this for a while! Good work.

toomany MBZ · #17 07-16-2008, 05:58 AM

Quote:

Originally Posted by NC Benz

Thanks Too Many!!! I have been looking for this for a while! Good work.

No prob, happy to help.

uvula · #18 07-17-2008, 06:44 PM

Quote:

Originally Posted by sixto

Behind the driver side headlight there's a 1.5" diameter cylinder. Spin off the tethered cap. A piece inside with electrical connectors is free to slide in the cap. Pull it out -- pull it to the end of its travel then rock it out. Carefully scrape off as much of the silicone goop as you can. Don't cut any wires, solder or traces. Use your imagination to figure out what insulating material you can fit between the cap and the sliding piece to put pressure on the solder joints. I used a couple of furniture pads. Some folks use a foam packing peanut or a cigarette butt. Put it back together and tighten it just enough to get the tach to work and maybe a little more. I owe you a worn silver rack damper pin if that doesn't do it.

Oh, also clean the magnetic sensor at the 1 o'clock position over the crank pulley.

This is a fantastic fix! I traced every wire in that circuit trying to figure our why the tach in my 300 SD worked roughly a third of the time. All to no avail...

...until I read this thread & wandered out to my car, pulled the cylinder, scraped off the silicone, tidied things up at the circuit board in the cylinder, stuck three used cigarette butts in there and put it all back together again. BOOM! The damn thing works like a champ.

Unbelievable. Thanks sixto!

82300sd · #19 07-19-2008, 07:21 AM

I would like to report that I was able to fix my tach too, by following sixto's advice. After 4 years of owning the SD with a non functioning tach, it now works great. Thanks.

Doug183 · #20 07-23-2009, 09:04 PM

I have an 1983 300D and am trying to fix the tach which seems dead. I will try the silicon removal and cigarette butt fix, but one other concern is that someone cut the wires to the tach amp, butt spliced red wire to wires and shoved exposed ends into the female receptacle for the amp - I assume to make a good connection. The wire are shoved into pin holes # 2,3, and 6. Is this right? Can anyone point me in the direction of a wiring diagram of this device or know the pinouts?

Thanks
Doug

techguy512 · #21 07-23-2009, 09:53 PM

Quote:

Originally Posted by Doug183

Can anyone point me in the direction of a wiring diagram of this device or know the pinouts?

I have a wiring diagram for the 300SD. This area of the schematic should be the same for the 300D. PM me with an email address and I'll forward it to you, since it's too large to post.

frank1943 · #22 10-18-2009, 08:00 AM

Dear TechGuy,

Thanks for all the hard work and information that you have seen fit to give us. I would like to request the aforementioned schematic. My email address is: frichards1943@verizon.net

I would also like any information on your new tach amp with the risk computer chip. Are you still providing them? How much would you charge now for the replacement?

My car is a 1982 300sd.

Thanks much,
Frank Richards, Virginia Beach, VA

techguy512 · #23 10-18-2009, 11:03 AM

Quote:

Originally Posted by frank1943

I would like to request the aforementioned schematic.....

Schematic and PM sent.........

jbritt1084 · #24 10-30-2009, 11:14 PM

Unbelieveable!!! Mercedes dealer wanted $500+ to fix...pulled it apart as instructed & whittled away while talking to my mechanic nieghbor (who thought I must be drunk) and ask my wife for where the furniture pads were...done!!! let my 3 year old fire her up and instant tach...THANKS!!!