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Passat instrument cluster in T3

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syncroandy View Drop Down
Yardie
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Post Options Post Options   Thanks (0) Thanks(0)   Quote syncroandy Quote  Post ReplyReply Direct Link To This Post Topic: Passat instrument cluster in T3
    Posted: 13 May 13 at 12:49
My T3's both have alternative engines, and for some time now I've been wanting to upgrade the instrument clusters to better suit the newer engines. I've therefore spent a fair chunk of time recently on fitting the Passat 3B instrument cluster (pre-Canbus), this involved physically fitting it, wiring it in, and making EPROM changes to work with the T3 fuel gauge.

I've already posted up on 80-90 about this, but after it cropped up in the context of Tim's flipped Passat gearbox, I'm posting up some info here too for those that haven't already seen it. Quite possibly other folk on here have done similar stuff, and it'd be good to hear about it.

To try and recoup some of the resources I've already sunk into it, I'm hoping to make an 'upgrade kit' of some sort available, which I'd anticipate primarily be of interest to those fitting alternative engines, either petrol or diesel.

It's still at protoype stage, and I'd welcome any feedback to help me improve the design before the first batch gets produced. One thing I've not cracked yet is modding the car cluster to work with the larger T3 wheel size, which means the odometer will under-read slightly unless a Dakota Digital box or similar is used. It may be possible to use a T4 cluster to work around this, though I've not yet got one to play with. I'm hoping to get it working with Subaru engines as well as VAG, though I've not done any testing of this yet. I may end up building my own adapter box if that seems necessary.

None of this is rocket science, I'm sure its all been done before, but from the feedback I've had already it seems there may be enough interest for it to be worth pursuing further. Anyway here are some pics, happy to answer any questions.



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Post Options Post Options   Thanks (0) Thanks(0)   Quote syncroandy Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 13:29
Correction re. speedo drive. I'm using a Syncro so my drive spins at more or less the same rate as a TDI car, so my odo is only slightly off. On a 2WD it will be about 50% off so correction will be required. One option with a 2WD is to ignore the existing speedo drive and fit a sender to a CV joint designed to generate 4 pulses/rev.

Edited by syncroandy - 13 May 13 at 13:31
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Titus A Duxass Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 13:54
An excellent start to this thread.

I have a set of Passat clocks.
I also have:
the sensor that sits over a CV joint and uses the screw heads to generate the pulses.
the cable loom adaptor
the speedo converter

So I've got all the gear but no idea.

For example - the signal from the pulse sensor/generator - do I wire this up to the clocks or do I feed it direct to the ECU.

So any light that you can shine on this subject will be rewarded with beer (if we ever meet).



Edited by Titus A Duxass - 13 May 13 at 13:56
Bollocks to it all!!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote syncroandy Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 15:03
Hi Titus, on the wiring diagrams I've looked at, the instrument cluster is the 'gatekeeper' for the VSS. The gearbox sender output connects to the cluster, where a correction factor (k-value) is applied to compensate for the wheel size on that particular car. The cluster then outputs the vehicle speed signal onto a connection on the relay plate (on CE2 vehicles) or onto a common connection in the dash harness (on later cars). The engine control unit then picks up the VSS for its own purposes, including operation of cruise control.

In your case, you need to correct the pulse rate coming from your CV joint sender before it gets to the cluster. So, connect the sender output to your adapter box input, then connect the adapter box output to the speed sender input on the cluster.

On your 3A cluster, the input pin number is T28/27, which on the other end of the cluster harness is on the blue connector U1, pin 11. U1 is the one with the locking pin centrally located.

The VSS output from the cluster is on pin T28/07, U2/02. The VSS input on a 68-pin ECU is pin T68/43.

I'll try to post up a table with the 3A cluster pinout mapping to the T3 dash harness, if that doesn't work I can email it if you want.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Titus A Duxass Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 15:18
Fantastic, thank you so much.
I'll pm you my email.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote syncroandy Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 15:48
Tried to post it here but this forum doesn't appear to support BBcode tables, I'll email it.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Gtavalanche Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 17:25
I'd be interest in ones of these when they're ready for the market.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote fufflenarnia Quote  Post ReplyReply Direct Link To This Post Posted: 13 May 13 at 21:35
I originally ran with the golf sensor being driven by the speedo cable with a 'speedpuls' unit from Germany to correct the signal - it was, frankly perfect.

When I did my gearbox swap I tried using the passat gearbox sensor, the signal was fair, but the needle was jumping a lot, so I have reverted back to the golf sensor. The question is, do I have a dodgy sensor, is emf effecting the signal or does the speedpuls not like the signal. I did not get any error codes from the ECU.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote syncroandy Quote  Post ReplyReply Direct Link To This Post Posted: 14 May 13 at 11:11
Leroy, cheers I'll add your name to the list of interested.

Steve, thanks for that, sort of confirms my concern that the 3-pin and 2-pin senders are different electrically. Having said that the older 3-pin sender seems to work fine with the later cluster, but maybe not the other way round.
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