wiring the Dual VR on a smd-3.57 board

http://jbperf.com/dual_VR/index.html

wiring the Dual VR on a smd-3.57 board

Postby pocpoc » Tue Nov 15, 2011 6:58 pm

Hello to all,

I have a short question.
Probably a typically noob's question but I don't found a clear answer to my question!!


I've wired my Dual VR like described hereafter:

VR- and ground are wired to groung pin of Q16. Q16 is not in place
VR+ is wired to pin 24 on DB37 main plug
+12 is wired to S12

more datas concerning the VR sensor itself: it's a 3wires one. At the end, near DB37 plug, the shield is wire to the VR-. Both are wired to pin 8 of main plug.

My problem is the following: when I switch on the car, not on cranking position, the RPM gauge is reading around 350 rpm. So fuel pump is already swicthed on and so on...

When I remove the ground (linked to pin3 of Q16): this problem disappear.

Have you already seen that and how could I solve it?
What do I must check?

Thanks a lot for your support.

POCPOC.
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Re: wiring the Dual VR on a smd-3.57 board

Postby jbelanger » Tue Nov 15, 2011 9:47 pm

VR- is not really meant to be connected to ground. It should be connected to the second wire on the VR sensor and the wire should also not be connected to ground.

But you say that you have 3 wires on your sensor? What are they connected to? Usually a 3-wire sensor is not a VR sensor but a Hall sensor.

Also, if you simply leave VR- not connected to anything, do you get an RPM reading when you crank?

Jean
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Re: wiring the Dual VR on a smd-3.57 board

Postby pocpoc » Wed Nov 16, 2011 5:43 am

Hello Jean,

thanks for your reactivity!

This sensor is a 3 wire (like a Hall sensor...) BUT it's a VR one.
You could see in attachment voltage value for different RPM, it's an extract from the workshop manual.

I've never tried with the VR- not connected.

In your opinion ground and +12 connected (from Q16 gnd pad and S12) are OK.
So it's a problem of VR-?

POCPOC
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Re: wiring the Dual VR on a smd-3.57 board

Postby jbelanger » Wed Nov 16, 2011 10:49 am

Yes, the 12V and ground connection are fine. And my guess is that the issue is on the VR- connection.

Jean
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Re: wiring the Dual VR on a smd-3.57 board

Postby pocpoc » Wed Nov 16, 2011 5:48 pm

Ok.
I will try with VR- unwired.
Do I must disconnect from the DB37 or on VR board?
If I disconnect from VRboard: ground and VR- will be at same potential because the VR- is connect to a pin linked to ground board.

Do I must check other thing?


Thank you,

POCPOC.
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Re: wiring the Dual VR on a smd-3.57 board

Postby jbelanger » Wed Nov 16, 2011 6:03 pm

I'm not sure I understand what you mean. Do you mean that the VR- at the sensor will be grounded? If that's the case, the best thing to do is to use another pin on the DB37 (one of the spare pins) and connect the sensor VR- to this pin and also connect the VR- on the dual VR board to that pin. But don't connect ground to it.

If that's not what you mean, just make sure the dual VR board VR- is not connected to anything for your test.

Jean
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Re: wiring the Dual VR on a smd-3.57 board

Postby pocpoc » Thu Nov 17, 2011 5:42 am

jbelanger wrote:I'm not sure I understand what you mean. Do you mean that the VR- at the sensor will be grounded?

If that's not what you mean, just make sure the dual VR board VR- is not connected to anything for your test.

Jean


today the VR- is connected to pin 8 of the DB37. This pin is at ground plane (no?).

So I will try:
1 - VR- only connected to the VR- input on dual VR board
2 - VR- connected to nothing

I'm right?

Thanks.

POCPOC
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Re: wiring the Dual VR on a smd-3.57 board

Postby jbelanger » Thu Nov 17, 2011 10:22 am

Yes, you're correct. Option 1 is the best solution if it works and should be the way to go. However, I have seen where this was a problem so it may need option 2.

Jean
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Re: wiring the Dual VR on a smd-3.57 board

Postby pocpoc » Tue Nov 22, 2011 5:42 am

Thanks Jean for your help!


Now I have a strong square shape seen by the MS3. Very good!

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