VN V8 Ignition Module Repair

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pman92
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VN V8 Ignition Module Repair

Post by pman92 »

Hey guys,
I've been given a faulty VN V8 ignition module.
I plan to repair it if I can. Not because I need to or have any use for it but because I want to and hopefully I can learn a thing or 2.
The person I got it off said when it failed it got very hot, hopefully this is normal and doesn't mean it won't be repairable.

I've found information about the operation of (I presume) similar Bosch module, which I've read and makes sense.
http://users.tpg.com.au/pschamb/boschrepair.html
I assume most of the extra electronics in the VN module is for the EST.

Also found plenty of information saying the fault it usually the main transistor, and it can be replaced with a MJ10012 packaged as T03, is the true? Is this the most suitable replacement?

Also trying to get my head around the operation of the EST.
I understand the distributer has a pickup with 30 degree open windows and 15 degree closed windows (45 degree per cylinder).
When bypass is not active (diagnostic mode, cracking speed etc), does the module switch off the main transistor and create the spark as the Hall effect signal switches high (window opens) or low (window closes, as in link above)
When bypass is active, I understand a delayed signal is fed back to operate the module.
I have read something about this being based off a 70degree BTDC signal from the previous Hall effect window (2x 15 degree closed windows, 1 30 degree open window, 10 degree base timing), delayed to the commanded value. However this doesn't make sense to me, because the 10 degrees is crankshaft speed and Hall effect windows distributer speed.
Can someone explain how the EST output is created?

Also is there anything else I should be doing other than changing the transistor?

Thanks in advance
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Gareth
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Re: VN V8 Ignition Module Repair

Post by Gareth »

I dont have anything to add but just wanted to say that I'll be watching this with great interest, i have a box full of dead modules, it would be great if you did a write up of this when you work it out :thumbup:
According to chemistry, alcohol is a solution...
pman92
Posts: 464
Joined: Thu May 03, 2012 10:50 pm
cars: HZ One Tonner
VE Ute
Location: Castlemaine, Vic

Re: VN V8 Ignition Module Repair

Post by pman92 »

I got myself a MJ10012 for $11 from the local jaycar stockist.
I've dismantled the module, and diode tested the old main transistor. It does have a 1.4v junction where the new one is 0.6v, but there is no shorted junctions. This makes me think maybe it isn't the fault.

The module looks like it is very similar to the one in the link from my first post. Obviously with a lot of extra components for the EST.
I'm thinking maybe the failure is the smaller transistor that drives the main one as in the link above.

I'll refit the main transistor and wire it up on the bench this weekend
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vn_ss_cm
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Re: VN V8 Ignition Module Repair

Post by vn_ss_cm »

any luck with this?

I have replaced the transistor in mine and now the car starts but then dies straight away!..hall effect is fine as it was replaced recently and tested with a working module
pman92
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cars: HZ One Tonner
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Re: VN V8 Ignition Module Repair

Post by pman92 »

It hasn't been forgotten I've just been busy with other stuff.

I've mounted it all on a plastic board and ran hook up wires to make it operate on the bench. Set up a light globe as the coil etc.

When I initially set it up it was working (grounding the hall signal would cause the light globe to light up).
And then it stopped working. I gave the smaller transistor a few taps and it started working again. So I'm pretty confident that is the fault but won't be able to prove it until it faults again?

Interesting things I noticed is its current limiting (can see the light globe dim slightly after initially being full brightness). And it doesn't actually require a moving hall signal to operate the coil (so if you switch the ignition on/leave engine off and the distributer is in the right spot, the coil will stay switched on while the ignition is on. Like an old points system if the points were closed).
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Tinker
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Re: VN V8 Ignition Module Repair

Post by Tinker »

I know this is an old post but has anyone fixed this module with success ?
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