Tachometer fix .... more swank than cigarette butt.

[David Dodge]

I tried several of the quick fix methods mentioned in regards to getting my tach to work.

They all seemed to work for maybe a day or two. It seemed that everything I put in there was squashed down to the point that there was no more spring or pressure being applied.

I got to thinking what could I put in there that would keep some spring. I decided to put rubber bands in the cylinder and snugged it down pretty good and it has been working ever since with no problems.

[jcd]

However, if anyone would like to try the cigarette butt approach, let me know. I'll be glad to send you some......I generate PLENTY every day.

JCD

David Dodge,

Could you provide some more description on your fix - like what parts, where is it located, etc. I've had a flaky tach on my '83 300D since I bought it. Some days it works, some days not. It feaks-out when I honk the horn or go over a large bump. I'm thinking I have a mix of mechanical and electrical issues, but I'd like to make some progress on this.

Thanks!

[fredjj]

I just purchased a 81 300SD and tried the cig. butt approach. This fix seems more permanent. Thanks for sharing with the group.

[David Dodge]

There's black cylindrical case on the drivers side engine compartment on the sidewall panel, If I remember right is about 5 inches long and about as round as a silver dollar. It has a plastic lanyard attached so as not to lose the top half when you unscrew it. When you get the top off, the female connection should be inside this piece. You have about an inch of room to grab on to this piece and pull it out. It will take some effort, but will come out if you have a decent grip. You will see on the bottom that there is a white waxy silicone substance on one end. Put the rubber bands in between the two parts and screw it down fairly firm. You may have to test the tightness + or - till it works just right.

Anyway this worked for me. Good luck

[engatwork]

Do the rubber bands go between the cap and the female plug in connector or between the parts that are exposed when the female plug connection section is exposed?
thanks

[David Dodge]

Here's an explanation from someone better able to describe the parts than I. I found this information on a previous tachometer thread from RSH. You can replace rubberbands where he uses cardboard if you think my method sounds better.... It worked better for me!

"The cylinder on the fender well is the diagnostic socket, sometimes referred to as the tach amp, there is a lead that runs from it to the tach sensor just as you observed. There are some tricks you can try to get the tach to operate. 1. Sometimes an engine thats almost twenty years old has alot of grease and grime and in the case of the tach sensor it can get really dirty at its pickup point and even though its pickup is magnetic I think it helps if the sensor is clean. 2. Unscrew the cap on the tach amp and look at the pins and mating sockets for corrosion, you can clean if necessary. 3. Separate the cap from the male portion of the pin assy, it will take a little pulling but it will seperate, on the back side of the male pin assy is a potting material (silicon rubber) check to see if it is intact and not allowing the pins to float excessively. 4. Cut out a piece of standard 1/8" thick cardboard in a circular shape the same diameter as the inside of the tach amp cap and position it inside the cap. 5. Install the male pin assy back into the cap. 6. Screw the male pin assy with cap to the female socketed base. 7. Start the car, the tach should now work, you may have to make adjustments as to how tight the cap is screwed on so that the cap with cardboard spacer applies the correct amount of pressure on the pins for good contact."