Tach installation in a 300D - PeachParts Mercedes-Benz Forum

juanesoto · #1 02-14-2007, 09:43 AM

Hello guys! What's up?

I just got my hand on this (check pics) and I was wondering if this can be installed in a 300D. What would I need? How complicated will that be?

Thanks for any advice you can give me!

winmutt · #2 02-14-2007, 10:20 AM

You dont have a tach pickup on that euro. Trust me it drives me up the wa.ll.

juanesoto · #3 02-14-2007, 10:41 AM

I know that. I have access to the parts needed. The pick up unit and the amplifier. I only need some guidance through the process. I also have doubt about the tach, is the same unit in both diesel and gasoline engines? I remember seeing a tach from a 300TD and I'm almost sure it had a 3-pin connector. The unit I have is for a 2-pin connector.

DeliveryValve · #4 02-14-2007, 10:43 AM

The 3 pin unit comes from a computer controlled tach (no tach amplifier)found in the 84-85 300d. The 2 pin comes from 82-83 300d's with the tach amplifier.

Yours is correct.

juanesoto · #5 02-14-2007, 11:10 AM

Ok, so I'm in the right track. Where is the pick up unit located? Maybe a pic... Any advice about how to wire the thing?

I have access to the parts at a local junkyard. All I have to do is know exactly what I need and go for a little junk diving.

I've heard that the tach was an optional item in euro models, so that they came prewired in case the buyer wanted the accessory. Is this true? How can I tell if my 300D is prewired?

winmutt · #6 02-14-2007, 01:27 PM

He has an NA. There is no place for the pickup to go. You will need to find another solution.

DeliveryValve · #7 02-15-2007, 03:58 PM

Quote:

Originally Posted by juanesoto

Ok, so I'm in the right track. Where is the pick up unit located? Maybe a pic... Any advice about how to wire the thing?

See attached pics. You will need figure out how to attach the magnetic peg on your orginal balancer and the RPM Pickup to the engine block. The next step is to route the wiring and find a power supply for the the Tach Amplifier and Tachometer. If you are successful in doing this project, you should post a "How To" here because a lot of people would like to know.

Good Luck!

EDIT: I am not sure if the peg/pin is actually "magnetic", I am only assuming.

pizzachef · #8 02-21-2007, 10:59 PM

I think I have what it takes!!!

Well, as far as the wire and sensor anyway, i saw what looks like a sensor near the balancer, although it was a little grime covered. And a gray wire leaving the sensor going to the drivers side wall near the wheel well. It ends at this thing in the picture, looks like a connector. It has a screw-on cover that I took off for the picture. Can I get a tach and run the wire from it to this thing? Do I need an amp? Where does the amp go?

Thanks for the help,
-Geoff

Hit Man X · #9 02-21-2007, 11:41 PM

My '85 is open like that too as I have the computer controlled amp. I would assume either of these two will work:

1. Just plug in that tach and see what happen

2. Plug in tach and install amp.

Hard to say as Euro vehicles have odd bits stock over the US cars.

FWIW - my 240D has the pin and bracket already.

DeliveryValve · #10 02-22-2007, 01:57 AM

Quote:

Originally Posted by pizzachef

.... Can I get a tach and run the wire from it to this thing? Do I need an amp? Where does the amp go?.....

The tach amp goes into that connector with the screw on cover. Now this part I am guessing base on my observation. If you look on the connector, you notice holes with numbers associated with them. #2 is gound and #6 is power and leads to the firewall. I think you will need to add in a wire for #3. Get the wire and plug for the back of the tachometer (instrument cluster) from the donor vehicle. The green-black wire from the tachometer plug goes to the #3 prong on the tach amp and the red-black one goes to switched power that you will need to find. Then hope it works!

EDIT: Added Picture of Tach Amp

#11 02-22-2007, 02:17 AM

Quote:

Originally Posted by rmarzan

EDIT: I am not sure if the peg/pin is actually "magnetic", I am only assuming.

It's not. It's just a pin. The sensor is magnetic.

As the pin enters the sensors magnetic field, it pushes up a voltage. When it reaches the center, it stops. As it leaves the magnetic field, it pulls a voltage down. In other words, it generates an AC voltage that the tach amplifier on the fender amplifies (duh) and sends to the tachometer. The tachometer is just a glorified AC voltmeter.

billybaru13 · #12 03-05-2007, 02:39 PM

any luck getting that tach to work?

I am trying to trouble shoot my own tach.

I have a 300sd and the tach has never worked since i owned it.

Do you need to have the tach amp to have the tach work? My plu has nothing in it. Just a cover.

Is there a way to measure to see if your sender is working? I assume that you could use your meter somehow ...

DeliveryValve · #13 03-05-2007, 03:28 PM

Sounds like you have an '84 or newer SD. The tach is computer controlled. Adding a tach amp will not do anything. If you wanted to use the tach amp, you will need to re-wire and have the '83 or older setup.

billybaru13 · #14 03-05-2007, 06:57 PM

Yes mine is an 84 ...

So can I stick my meter in any of those 9 pins on the connecter to see if my pick-up is working?

DeliveryValve · #15 03-06-2007, 03:17 AM

No. That pickup is for diagnosis information only. Your tach pickup is actually located on the bellhousing plate, it gets the signal off of the flywheel. The wire then leads to a computer on the passenger side kick panel. You will have trace your issues through there. I am not familiar with that setup so hopefully someone else can help you out.