tachometer frustration - Page 3 - PeachParts Mercedes-Benz Forum

toomany MBZ · #31 05-14-2011, 09:24 PM

Not sure, I'm only familiar with auto trannies.

But, no, the egr will not accept the flywheel signal, (or vise-a-versa) a completely different animal, AFAIK.

Ya Mar · #32 05-14-2011, 09:52 PM

Hey toomany,

Well it looks like the trans sensor will not it on the manual transmission.

Since the two sensors are not interchangeable, I'm going to need to find an amp and a 2 prong tach.

Bummer!

Thanks for all your help!

toomany MBZ · #33 05-14-2011, 09:57 PM

I still have that cluster, with a two pronged tach.

There was a poster here, Techguy 512 that had solid state amps, but otherwise, they're getting pricey.

Ya Mar · #34 05-14-2011, 10:27 PM

Here is a link Army posted on his thread.

http://mbelectronicupgrades.com/Tachometer_Amp.html

$49.00 for a digital replacement.

Do you think this will work with the dustcap diagnostic port I have now?

Or do you remove the diagnostic port and put this in it's place?

Ya Mar · #35 05-14-2011, 10:32 PM

Nevermind, answered my own question.

The above digital amp is not compatible with the diagnostic port as it lacks a metal contact in port 3 (signal out to tach)

Is it possible to rewire the diagnostic port to add the signal output in port 3?

funola · #36 05-14-2011, 10:32 PM

Another possibility is if you can find a EGR computer from a 240D (year 83 has one for sure, maybe 84 also). then you don't need a tach amp.

Here's a thread with some pics that may help you.

http://www.peachparts.com/shopforum/showthread.php?p=2524588

The cluster pic (2 prong) is marked + on one terminal and W on the other (which is the signal from the tach amp). I am not familiar with the 85 3 prong cluster. Maybe the extra prong is just a ground? If everything else is the same as a 2 prong cluster, it should work if you wire up the respective terminal correctly.

Take a look at FSM 82_300 warning/indicator gauge page, it shows wiring for the TDC sensor, TDC amp, tach and power distribution to the tach.

DeliveryValve · #37 05-14-2011, 11:06 PM

Quote:

Originally Posted by Ya Mar

Nevermind, answered my own question.

The above digital amp is not compatible with the diagnostic port as it lacks a metal contact in port 3 (signal out to tach)

Is it possible to rewire the diagnostic port to add the signal output in port 3?

Third time I posted this for you. Twice here and once on the other thread.

http://www.peachparts.com/shopforum/showpost.php?p=2418514&postcount=10

Going the EGR computer retrofit route for only tach functions is not worth the time and doesn't make sense when you can easily accomplish the same thing with a tach amp and a couple of wiring.

.

.

Ya Mar · #38 05-15-2011, 12:42 AM

Deliveryvalve,

Thank you for your posts. I did read the link thoroughly and found it helpful.

I was originally trying to work with what I have rather than buying extra parts. That's why I continued trying to use the ERG computer. Which may have worked if I had an auto trans.

Thanks again,
Ya mar

techguy512 · #39 05-15-2011, 02:45 PM

Quote:

Originally Posted by Ya Mar

Is it possible to rewire the diagnostic port to add the signal output in port 3?

Yes it is easily done. All you need is a female pin inserted into pin 3, with a wire run thru the firewall to the input pin on the two pin tach.

I'll help you if you want.....

Ya Mar · #40 05-16-2011, 10:34 PM

Quote:

Originally Posted by techguy512

Yes it is easily done. All you need is a female pin inserted into pin 3, with a wire run thru the firewall to the input pin on the two pin tach.

I'll help you if you want.....

Hey TechGuy,

That's great news, I will try to get it working.

Where do you suppose I could find a female pin to insert?

Would I run the wire out of the top of the amp?

Stretch · #41 05-17-2011, 03:29 AM

Quote:

Originally Posted by Ya Mar

Hey TechGuy,

That's great news, I will try to get it working.

Where do you suppose I could find a female pin to insert?

Would I run the wire out of the top of the amp?

Any decent automotive repair shop should have a nice selection of pins and connectors.

Re-wire the plug that fits in the amp for a nice factory look!

Ya Mar · #42 05-17-2011, 12:56 PM

Cool! Thanks All.

Ya Mar · #43 05-17-2011, 12:59 PM

I realized when I installed the sensor the tip of it got clipped by the flywheel. Picture attached....

I'm hoping I can still use it since I just bought it! Maybe some electrical tape?

Ya Mar · #44 05-17-2011, 01:10 PM

Hey Techguy512,

So I just went out and looked at the diagnostic port and I don't really understand how adding a female pin and running a wire out from the 3 port to the back of the tachometer will send the signal.

Are you saying I can use the diagnostic port once I have the amplifier screwed on top?

Or can I use the diagnostic port without an amplifier?

Right now I just have the dust cap screwed on top.

Lemme know what you think?

funola · #45 05-17-2011, 01:24 PM

Quote:

Originally Posted by Ya Mar

I realized when I installed the sensor the tip of it got clipped by the flywheel. Picture attached....

I'm hoping I can still use it since I just bought it! Maybe some electrical tape?

Measure it with an ohmeter. As long as it is not open circuit (infinite ohms) or shorted (zero ohms) and shows somewhere around 80 ohms it should still work. Put some epoxy to seal it from the environments before installing it.