Tachometer wiring confusion

[ein bora]

I’m having problems wiring the tach on my b5 passat gas to diesel project. I’m using the dakota digital DSL-1 and can’t seem to find the pin for running the tach. As I’m not using the ECU and from what I understand the tach gets it’s signal from a speed sensor mounted on the block. I tried connecting the dakota to the speed sensor pin’s on the ECU connector - but nothing.
Another thing I read is that the signal also comes from a crank positioner, but I can’t seem to find nothing supporting that in the bentley.
I then took the cluster apart and using an ohm meter - I tried to pin point the tach's terminal's on the wiring connector going into the cluster, but I couldn't even pin point that, nothing from the tach terminates directly to the clusters connector – soooo I thought I could just wire direct to the tach itself, thereby bypassing all the other stuff and just run the leads separately. Problem is there’s four terminals and I think I only need three, power, ground and signal.
Any wisdom or guidance appreciated. Thanks.

[CRSMP5]

well bout to run into same thing on b3.. so lets hear it..

[92EcoDiesel Jetta]

If the cluster is CE2, tach input pin is T28/10.

[ein bora]

I contacted Dakota Digital on this and this is the response I got. Not good!

Quote - What year is your Passat?   We found that many VW tachs, after ’88, would not work with our DSL interface due to built in filters for the high voltage spike from the coil.  Cars built after ’96 used data bus to the das from the ECU.  In ’08 they switch to CAN bus.

And later this - By 2000 the dash was running off the data bus from the ECU.  Without the ECU it is doubtful that much of your dash will function at all.  That is also why you cannot find a single wire for a tach input.

So the dakota digital is of no use for anyone trying to convert certain vw. I took the tach off of the pc board and tried to figure out how to wire it up direct to the DSL but to no avail. I was hoping that might work as I could wire it separate from the cluster.
It's a shame as I would have liked to keep the original cluster and also have a tach.
Not sure what to try next option wise.

[rodpaslow]

I just read this quickly, but the signal for the Dakota Digital will come from your W- on the alternator. My A3 golf has a bosch style connector (square two pin) with one wire connected.  I think the one wire is the D+ on the alternator.  Anyway the second wire is not in the connector is for the W.  I just found a bosch connector with two wires and hooked it the second wire up to the Dakota Digital.

If your using a stock tack, I'm not sure how to do that, but this should get you a signal to the dakota digital unit without trying to hook up an aftermarket crank sensor of some kind.  I used a aftermarket VDO tack and replace both the tack and speedo with vdo electric units since speedo uses a vss sensor from the trans.

[ein bora]

I've had enough and I'm going with a total custom cluster. I like the VDO gauges too so I'm going that route as well.

Thanks for the responses, hopefully others will read this and not waste their money on the dakota.

[fatmobile]

 I've heard of people that used a dakota digital with a stock tach.
 The tach circuit hasn't changed,.. from '84 to '92.
 Same pulse conditioning, chip same circuit.

[R.O.R-2.0]

I've heard of people that used a dakota digital with a stock tach.
 The tach circuit hasn't changed,.. from '84 to '92.
 Same pulse conditioning, chip same circuit.

B5 is not 84-92 tho..

[ein bora]

Not being one to give up and for those who are interested - I finally got a tach to work in my b5 conversion. What I did was buy a gas cluster out of a 81 rabbit, removed the tach and mounted it into the original tach’s location on the b5’s cluster.
I had a few challenges to over come, like the tach’s post (the post that the pointer sits on to) was to short and a different diameter than the b5’s, the rabbit’s tach was not strong enough to move the larger therefore heavier b5’s pointer, and then there was clearance issues.

In the end I used my dakota digital, the rabbit’s tach and the pointers out of a mk3 and she works. Bonus thing is everything else still works too, which finally puts an end to this chapter of the conversion.
Now on to the next challenge.....