Duffy's 1/71 Series 1 240z build

[Zed Head]

On 8/15/2022 at 7:45 AM, duffymahoney said:

The coil positive has a full short in it.

 

5 hours ago, duffymahoney said:

But I found my first melted wire.

I don't want to muddy up the waters either.  But a "full" short would completely fry the insulation and the wire very quickly.  That wire has just seen too much current for too long.  But there is a load, some resistance, between the source and the ground somewhere.  Have you measured resistance through that IAC valve?  Easy to do and worth verifying.

[SteveJ]

57 minutes ago, Zed Head said:

 

I don't want to muddy up the waters either.  But a "full" short would completely fry the insulation and the wire very quickly.  That wire has just seen too much current for too long.  But there is a load, some resistance, between the source and the ground somewhere.  Have you measured resistance through that IAC valve?  Easy to do and worth verifying.

That's why I'm trying to get more information on the testing methods. There could be a hot spot from corrosion at the black/white, possibly short duration short circuit in the past, or someone tapping into that circuit downstream, increasing the load on the circuit.

[duffymahoney]

I will start doing more testing later.  I will get details on my meter and what I am seeing.  I feel like this all started when my son decided to leave my car in the on position overnight.  But maybe not.  

 

The short is strong enough now, to drop voltage down enough to cause the haltechs relays to drop connection and cause the ecu to turn off, while cranking.  It's how I started down this fun rabbit hole.  I can also smell, burnt wiring when the key goes to on.  Sadly it's not as simple as just finding another keyed 12v for the haltech, I will need to fix this properly.  

Edited August 16, 2022 by duffymahoney

[SteveJ]

That's a good piece of the puzzle. Did you have the points ignition or a first gen Pertronix in the car when he did that?

The worst case scenario is that I can probably walk you through making a replacement for that wire that you can "graft" into the dash harness. You know you wanted to have a reason to pull the dash. 😉 

[Zed Head]

2 hours ago, SteveJ said:

Did you have the points ignition or a first gen Pertronix in the car when he did that?

I think that he has a Hall sensor on a modified Jeep CAS.  And he has coil on plugs, AKA COP, controlled through the Haltech system.  Could be a coil circuit in the Haltech ECU, or the tach circuit with all six coils ganged, or maybe the Hall sensor on the CAS.  

Lots of things to check.  Meter time.  Check, check, check , check...

[SteveJ]

17 minutes ago, Zed Head said:

I think that he has a Hall sensor on a modified Jeep CAS.  And he has coil on plugs, AKA COP, controlled through the Haltech system.  Could be a coil circuit in the Haltech ECU, or the tach circuit with all six coils ganged, or maybe the Hall sensor on the CAS.  

Lots of things to check.  Meter time.  Check, check, check , check...

So that would beg the question about where he tapped into the ignition circuit to begin with since he said he didn't know how the circuit was routed. More questions than answers.

[duffymahoney]

First test. This is one of the black and white wires for the ballast/ coil. Grounding to my shock tower. Klein  MM200 multimeter. 
 

Both the behind the tach is unplugged and so is my keyed ignition 

Edited August 17, 2022 by duffymahoney

[duffymahoney]

4 hours ago, SteveJ said:

So that would beg the question about where he tapped into the ignition circuit to begin with since he said he didn't know how the circuit was routed. More questions than answers.

Well I thought I knew exactly what it was. 12v positive for the coil. Which I wasn’t using. Since I have coil on plug. Getting fed directly from my ecu. I thought it was a simple way to wire my iac. But that turned out to be less. I regret it for sure.  It would have been easier by a lot, to just run a circuit off my haltech. Whoops 

[conedodger]

Steve, gather your tools and head for Idaho. Beer is on Duffy. Oh, and some late season wakeboarding!

[SteveJ]

11 hours ago, duffymahoney said:

First test. This is one of the black and white wires for the ballast/ coil. Grounding to my shock tower. Klein  MM200 multimeter. 
 

Both the behind the tach is unplugged and so is my keyed ignition 

Now THIS is something I can work with. The good news is that this wire is not shorted to ground. While 15 ohms is low resistance, you could be reading through other branches on the circuit. That resistance would equate to less than 1A of current when energized. You just don't want the end of the wire floating around in the engine bay where it could short while you're driving. 

[duffymahoney]

1 hour ago, SteveJ said:

Now THIS is something I can work with. The good news is that this wire is not shorted to ground. While 15 ohms is low resistance, you could be reading through other branches on the circuit. That resistance would equate to less than 1A of current when energized. You just don't want the end of the wire floating around in the engine bay where it could short while you're driving. 

Well interesting, I will have to look which wire this is, ballast or off the back of the tach, I assume an ohm reading will be best for that.  I see the ballast circuit goes off to other branches, and would be a not as nice spot for me to tap 12v from.  I will ohm check the rest of the ignition wires, but they also seem to go off and branch.  I will put a fuse inline no matter what I do.  

What circuit would you tap for the keyed 12v to my haltech?  Behind my dash I found two, one was defrost(unplugged since I got the car) and the other is a ?.  I was using the defrost, it's just a relay switched 12v, so very thin wire, so I assume low amp draw.  

 

1 hour ago, conedodger said:

Steve, gather your tools and head for Idaho. Beer is on Duffy. Oh, and some late season wakeboarding!

I do own a brewery and a wakesurf boat:) Come on up. 

[Blitzed]

Duffy,

Have a 73, so don't want to assume your stock ignition harness is the same wire color combo. Remove ignition switch cover behind the steering wheel and test the 5 pin connector plugged to the back of the ign key switch. Believe it's the B/W wire for 12v switched on (it's been a year and reassembled). Attach the pink wire from the Haltech ECU.