my tach amp wires got pulled out of the socket today i've looked around not found anything can anyone tell me the color of the wires for the #2,3 and 6 going into the tach amp?

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

If I may recall,

#2 is ground (not sure what color but maybe brown)
#3 is green-black (goes to directly to the tach)
#6 is red-black (switched power)


Hope this helps.

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1983 123.133 California
- GreaseCar Veg System

Well, I do have a picture with the socket cover removed, but now I can't find it. This schematic should help, you'll need to use a multimeter to figure out which ones are hot and ground.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

Brown is always ground.

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Gone to the dark side

- Jeff

OK Now ya done it... I may have to go out and build these puppies.... The Variable Reluctance amp (IC) is available for $3.60 each. I have already picked apart the sealant on one of these.

I am tired of my Tach flopping about (rarely) or just showing ZERO(most of the time).

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NC Benz
Fuquay-Varina, NC
1979 300D
1983 300D Turbo 260,000 Miles
1984 300D Turbo 345,000 Miles (sons car)
OBK #31
1998 Ford Expedition 5.4l (fer Haulin'!) 145,000
1973 19' SeaRay with 115 Mercury TOWER OF POWER!
Club Car Golf Cart 36V
Ex toys:
1967 Mustang 289 (First Car)
Fiat 124TC
1975 Honda CVCC
1980 Audi 5000 Turbo

I used a microcontroller. About 1/4 the cost of the LM1815.

Of course, you need to program it.......

Designing a Better Tach Amp

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Bob
'82 300D Petrol B-G Metallic

make too i think mine's busted after fiddling with the wires for about 30 min i broke on of the ones off on the base the female that fits into the #6 socket so now i've gotta find another to see if mine was just not making contact or what the silicone and whatever was holding the #2,3,6 wires was shot 25 yrs of heat has everything looose... so i'm up for something that replaces this junk and makes my tach not look like a top fuel dragster tach.

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

Here's a link to my post after reverse engineering the tach amp:

How the Tach Amp Works

If you follow the links to the second page, I posted a simple schematic for a circuit you can put together to test your tachometer.

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1984 300TD

This schematic has some glaring errors - be careful. For instance, pins 8 and 9 are connected together - which is problematical since pin 9 is the input from the variable reluctance sensor and pin 8 is ground! Also the inductor between pins 2 and 3 of the LM1815 isn't an inductor - it's a 0.0033 microfarad polyester capacitor, etc. Use the one I posted in my explanation - I took a Tachometer Amplifier completely apart and checked out each component individually.

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1984 300TD

Honestly, all I ever used this schematic for was the pinout for the amp in the upper right corner...I don't remember where it came from, but it was on this forum somewhere. Thanks for the info...I'll save yours too for future reference.

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

one of the female pins in the lower portion is broke any ideas on where i can find a replacement?

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

How's it broken? You can pop the lower part open and see what's under there...they're just female bullet connectors crimped/soldered to a wire. I don't know if a regular female bullet connector will fit right in that space, but you could give it a shot. Or take apart another connector in the car that you don't need...they're all over the car. Or a junk yard...

Hey, I found my pictures! Here's the connectors...

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now

yah that's the ones that are broke off i haven't looked much i have a tiny tach digital tach but i can't see it at night so i might fix it or might keep it taped up and say heck with it. I'd like to find some replacement ones just incase tho i've tried the normal bullet ones and they are a bit too big to fit in the plastic housing.

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2004 Infiniti G35 3.5L 6mt Coupe 73K miles 25.6mpg ytd
2001 Green Audi TT 225 AWD Roadster 71K 6sp 30.9mpg >>STOLEN<<
1982 300D Turbo 231K 120hp? 28.1mpg YTD

I thought the regular female bullet connectors might be a little too big, I've never tried though. Well just about every electrical connector in the car has these female bullet connectors in them. If you can find a junk car, you could score a good sized handful. Or take apart another connector in the car, like one of the rear door switches (my car doesn't do anything when you open the rear doors anyway).

What kind of digital tach to you have? Where is it connected?

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1985 300TD-euro 352,000 mi
1974 240D (1?)52,000 mi - has a new home now