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ukcats07

Ignition wire (BW) shows 12v in "LOCK"

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I'll start off by saying I solved my problem, but I'm unclear of why it worked. 

 

Bottom line is that I was receiving 12v on the Black/White keyed wire while the key was in the “LOCK” position, 0v in “OFF” and “ACC” then 12v in “RUN” and “START”.  All of this is normal with the exception of the “LOCK” position.  Measurements were made at the ignition switch.  I was also getting ground indications from this wire (one side of the multi-meter on the B/W and the other would have continuity when touched to any ground on the car). 

 

My Black/Yellow crank wire was also spiking around 6v if I turned the key slowly from “LOCK” to “OFF” (which resulted in a WTF moment when the starter kicked over), but otherwise only showed 12v in “START” and also didn’t spike if I turned the key rapidly from “LOCK” to “OFF”. 

I’ve “solved” the problem by removing the Air Cond (factory option, but none installed for this swap), Wiper motor, and Flasher fuses which resulted in normal behavior of the ignition switch wires when turned to the appropriate location.

 

I’ve attached my BLUE, GREEN, WHITE, BLACK dash to engine harness plug pin-outs, marked-up body electrical page from FSM and pictures of my power distribution to the harness. 

I’ve stared at the wiring diagram and cannot figure out why removing those fuses result in normal behavior.  Even worse, I have no idea how this wire is getting 12v when the key is in the “LOCK” position.  Any help or insight would be beneficial.  I suspect something with the Flasher circuit considering it is battery hot at all times and is the logical choice for why a wire that shouldn’t be hot was showing 12v. 

 

Background

1973 240z, been the owner for the past 13 years.  PO didn't hack anything up, I received it with no engine/transmission in preparation for a 302/T5 swap.  My current setup is a 5.3L/T56 using a re-worked truck harness and PCM (did it myself and very familiar with most every wire) and EZLSX Power Distribution Module for power delivery from the PCM.  My power distribution for the engine harness and rest of the car is through a Littelfuse 07981003ZXS LTX MEGA & MIDI Fuse Block Kit.  I have a brand-new battery and have verified LS and Z harness grounds are good.  My Z fuse block, and wire harness in general, are in excellent condition. 

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I removed my Z engine harness and modified it wire-by-wire to remove wires that were not needed for this swap.  I have attached my pin-outs for the 4 colored connectors under the passenger side of the dash.  Generally speaking, only lights, power, wiper motor and horn wires remain.  The Black/White, Black/Yellow and Green/White are snaked into the car to connect to the EZLSX PDM through a weather-pack connector. 

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My large gauge White and White/Red wires are running the littlefuse fuse block kit on the same 40A fuse.  My 12v source for the PDM is also on this fuse.  My headlights are on a different fuse through a relay block as well as the taurus fan. 

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IMG_20200921_225600.jpg.ca005b1566c08178cd4bde96f2060144.jpg

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12 hours ago, ukcats07 said:

My Black/Yellow crank wire was also spiking around 6v if I turned the key slowly from “LOCK” to “OFF” (which resulted in a WTF moment when the starter kicked over), but otherwise only showed 12v in “START” and also didn’t spike if I turned the key rapidly from “LOCK” to “OFF”. 

 

Check the wires at the back of the ignition switch.  There's only four.  Sounds like the electrical portion of the switch is worn out and shorting.  You can get replacements.  There's a screw that you have to drill or cut the head off of.  Anti-theft measure.

 

image.png.e843e8bb2413c994c55830a072327c7a.png

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6 minutes ago, NewZed said:

 

Check the wires at the back of the ignition switch.  There's only four.  Sounds like the electrical portion of the switch is worn out and shorting.  You can get replacements.  There's a screw that you have to drill or cut the head off of.  Anti-theft measure.

 

image.png.e843e8bb2413c994c55830a072327c7a.png

I have a 5 point ignition switch in my Z.  My Dad gave me a spare switch and lock combo that I tested and it checked out good as well.  To be clear, my plug that goes into the ignition on the steering wheel has five wires-- W/R power, L/R accessory, B/W ignition, B/Y start, G/W tach-resistor.  I tested for continuity at each spade and it all checked good--is that sufficient testing for an ignition switch?  Also, I'm still unclear as to why it operates normally now that the fuses are removed.

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13 hours ago, ukcats07 said:

Bottom line is that I was receiving 12v on the Black/White keyed wire while the key was in the “LOCK” position,

 

You described a whole bunch of stuff.  It's not clear where on the "B/W" wire you measured.  And there's a lot of B/W wires in the car.

 

If you're not getting power through the switch with the key in the Lock position then the power on the B/W wire is coming from a short or some other weird wiring thing.  You said it all tested "good" which means that there was no continuity from the power wire through the switch with the key at Lock.

 

Disconnect the switch entirely and put it all back together.  If you still get power on the B/W wire then the Lock position on the switch is irrelevant.  Forget about the switch and keep searching.

Edited by NewZed

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2 minutes ago, NewZed said:

You described a whole bunch of stuff.  It's not clear where on the "B/W" wire you measured.  And there's a lot of B/W wires in the car.

 

I measured the B/W wire at the ignition switch, in the plug.  What I don't understand is how I was getting 0v in OFF, but suddenly receiving 12v when turned all the way to LOCK.  The wiring diagram is unclear, but I assume that none of the contacts (with the exception of the W/R wire contact) should be hot in LOCK.  I removed the key assembly as a culprit by testing another known good key with my 5 pin ignition switch and I only received continuity on the appropriate pins when it was turned their respective positions--i.e. only the ACC pin had continuity when the key was in ACC, etc.  

 

9 minutes ago, NewZed said:

If you're not getting power through the switch with the key in the Lock position then the power on the B/W wire is coming from a short or some other weird wiring thing.

 

I'm leaning towards a weird wire thing with my ignition wire circuit and the air conditioning, wiper, or flasher circuit.  I'm really just trying to make sure I'm on the right track before I start hunting and pecking.  

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The other thing that's not very clear is the 2 wires on the lock assembly with male spades.  I believe they are for the door buzzer and door closed switch, but not sure how they work with respect to key position and whether they can somehow be tied into the other parts of the cars wiring unintentionally.

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Disassemble the electrical switch from the mechanical portion and see if it works correctly.  Maybe the electrical portion is over-rotating.

 

You're describing two things happening that can't both be correct.  The swatch tested "good", but it allowed power through at Lock.  

 

Here's the 5 contact diagram from 1976.

 

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I'll put this up here....was useful to me when I had a failing switch in my ignition switch (i.e. the non-keyed barrel behind the keyed portion of the ignition switch).  It's really nothing more than a visual representation of the information you guys have already posted/discussed. 

IG switch wiring schematic.png

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35 minutes ago, jhm said:

I'll put this up here....was useful to me when I had a failing switch in my ignition switch (i.e. the non-keyed barrel behind the keyed portion of the ignition switch).  It's really nothing more than a visual representation of the information you guys have already posted/discussed. 

IG switch wiring schematic.png

 

Actually, that fills out the thread.  I was looking for a good image of that but didn't find one.  You can see what should have power (continuity from the B terminal) at each position and test those.

 

p.s.I think that the R, IG, S, B, and A are molded or printed on the back of the switch.

Edited by NewZed

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Thanks for all the input.  My ignition switch checks good when disconnected from the lock assembly.  I'm going to focus on the battery hot circuits and see if a wire is mixed up somewhere giving power to the BW wire somehow.  I can deal without the wiper and flasher circuit for the time being until I find the problem.  

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