Wiring all components for the LSX Swap

[kj280z]

I have been searching and have not found a thread that sufficiently covers this topic. I'd like for this thread to be the place where we share all of our knowledge on wiring for the LSX swap.

 

As part of my swap, we have been going through every single wire in the stock harness (1975 280z) and eliminating all the unnecessary wires as well as (more importantly) identifying all the wires that need to be retained for various reasons.

 

What we're finding is that in many cases when we trace a wire and look it up in the wiring diagrams there are several differences and incorrect information in the books! Granted they are 30 years old but there's quite a bit of stuff in the harness that has been quite surprising. (We even found wires for factory fog lights in the harness!! - never knew they were there!)

 

As part of our exercise, we're rewiring the dash in a few instances to accommodate several new items as well as to insure that the gauges operate properly. We also are eliminating the fusible links in favor of a maxi fuse block.

 

Most of the wiring, while overwhelming is pretty straightforward if you take your time. Some have probably not gone as far as we have, but anyway...

 

I have a few questions to start this topic off, then we'll begin to share in some subsequent posts on this topic the things we've learned.

 

Here's some questions that we're having some challenges with conflicting information in the wiring diagrams:

 

1. There is a black/white wire that comes off the ignition switch - It's labelled 3 different things in my books. We assume this used to go to the ground on the distributor, but it's also labelled "ALT". My assumption at this point is that it is no longer necessary. What have you guys done with it?

 

2. What wire are you using off the dashboard controls to actuate the magnetized clutch to turn the AC on? The JCI compressor is a single black wire... The GM compressor had a 3 wire harness.

 

3. The GM PCM wiring harness has an "AC" wire - We assume that this wire needs a signal (positive or negative??) so the PCM knows to increase the idle when the AC is on... Any suggestions? Or is this wire used for something else related to the AC?

 

4. Does the GM check engine light pull to ground or does it send 12V to light up the light?

 

5. What have you guys done for the backup light wiring? The connector is way too close to the tunnel and it will not plug in.

 

6. What have you guys done to make the stock voltage gauge work correctly since the "charge" light which was in the circuit to turn on the old Datsun alternator is no longer needed?

 

I will share all of the solutions to what we've already done on this post with pictures. It would be great if you guys could do the same as well.

 

Thanks for your insights - I think this post will be invaluable to future guys doing this swap.

Edited November 20, 2010 by kjones

[mxgsfmdpx]

Appreciate this!

[Boy from Oz]

..5. What have you guys done for the backup light wiring? The connector is way too close to the tunnel and it will not plug in...

Purchase a 90 degree reverse switch and pigtail as supplied on t56s fitted to Mustangs - not sure which model/s.

[kj280z]

Purchase a 90 degree reverse switch and pigtail as supplied on t56s fitted to Mustangs - not sure which model/s.

 

GREAT! I have located this switch at Autozone. It's out of a 2001 (probably other years as well) Ford Mustang GT. Here's a link to it: http://www.autozone.com/autozone/parts/Duralast-Back-Up-Light-Switch/2001-Ford-Mustang-GT/_/N-jfab1Z9cio2?counter=1&itemIdentifier=739222_0_0_3498,91964 The price on their website is $101, but I'm sure I can find it much cheaper.

[m1noel]

For the ac I just used the wire that used to run the magnet clutch on the L6- on my 78 it was blue. Didn't use the wire from the PCM. And my idle doen't change when the ac is on.

Edited November 20, 2010 by m1noel

[h4nsm0l3m4n]

GREAT! I have located this switch at Autozone. It's out of a 2001 (probably other years as well) Ford Mustang GT. Here's a link to it: http://www.autozone.com/autozone/parts/Duralast-Back-Up-Light-Switch/2001-Ford-Mustang-GT/_/N-jfab1Z9cio2?counter=1&itemIdentifier=739222_0_0_3498,91964 The price on their website is $101, but I'm sure I can find it much cheaper.

 

Thanks so much for finding this! I'm having as hard time dealing with this issue myself. I looked up the same part at RockAuto.com and found a little more reasonable price. $26 for the same part.

 

[kj280z]

For the ac I just used the wire that used to run the magnet clutch on the L6- on my 78 it was blue. Didn't use the wire from the PCM. And my idle doen't change when the ac is on.

 

Thanks - again the Nissan Wiring diagrams are not accurate (I have 3 different versions)

 

I guess the disparities are caused by the differences between cars with and without factory AC. My car did not have AC so I added all the dashboard controls and AC stuff out of a 1975 280z (same year as mine). I cannot find the blue wire in my harness which I assumed would have been in the harness regardless if it had Factory AC or not, but it's not there. I will post more on this subject as we figure out a resolution.

 

Does the blue wire pull to ground or have 12 volts when actuated? Does the black wire on the JCI compressor get hooked up directly to the blue wire? If it pulls to ground how does the clutch get actuated?

[BRAAP]

Purchase a 90 degree reverse switch and pigtail as supplied on t56s fitted to Mustangs - not sure which model/s.

 

Nice find. Wish I would've known about his a few months ago. I ended up building my own 90 degree pigtail for tunnel clearance, this is much nicer.

[80LS1T]

Man I could have used that switch 5 years ago for my LT1 T56! My switch connector touches the tunnel but hasn't given me an issue.

 

Rockauto part # MOTORCRAFT Part # SW5857

 

Nice find!

[kj280z]

As we work this I want to continue to update this post.

 

For wiring the AC, we finally found the correct wire. It's a Blue/white wire which is in the console harness. The wiring is as follows:

 

The Blue/White provides 12 volts to the AC ref wire in your LS1 harness. If you've switched to the JCI AC compressor, you'll notice that it only has one single black wire. The stock LS1 compressor had a 2 wire connector. In the 2 wire connector there should be a green wire. The green wire is connected to the black wire on the JCI compressor. When the Blue/white wire provides power to the AC ref wire, the GM PCM turns the compressor on. I have not tested this yet, but I'm 99.9% sure this is right. Also, I have to find a dryer with a high/low pressure switch which also get's wired into the circuit.

 

If any of you have suggestions on what dryer you used and how you wired the pressure switch please share what you did!

Edited November 23, 2010 by kjones

[nocones]

I'm about to wire up the Check Engine Light/Malfunction Indicator Lamp too and am pretty sure that the PCM provides ground and the other wire for the light goes to switched power/ignition. That is my interpretation of the LS1 wiring diagram anyway. However, I'ld like to hear confirmation of this from someone else.

 

I've attached the portion of the wiring diagram which shows the connection. The Malfunction Indicator Lamp is shown on the top left corner.

2000 wiring camaro 5.7L 4of4.pdf

[BRAAP]

I'm about to wire up the Check Engine Light/Malfunction Indicator Lamp too and am pretty sure that the PCM provides ground and the other wire for the light goes to switched power/ignition. That is my interpretation of the LS1 wiring diagram anyway. However, I'ld like to hear confirmation of this from someone else.

 

I've attached the portion of the wiring diagram which shows the connection. The Malfunction Indicator Lamp is shown on the top left corner.

 

 

That is correct. The PCM pulls to ground.

[nocones]

sorry about the multiple postings!! I was getting a server error everytime I tried to post it and didn't think it was going through!

[BRAAP]

sorry about the multiple postings!! I was getting a server error everytime I tried to post it and didn't think it was going through!

 

No problem. For what it's worth it's not your computer, the forum software is buggy and we hope to have it fixed in the next few days, Sorry for the inconvenience guys.

 

In the mean time, you only have to click submit once, the post will be posted even though the forum hangs or gives an internal server error message.

[kj280z]

I'm about to wire up the Check Engine Light/Malfunction Indicator Lamp too and am pretty sure that the PCM provides ground and the other wire for the light goes to switched power/ignition. That is my interpretation of the LS1 wiring diagram anyway. However, I'ld like to hear confirmation of this from someone else.

 

I've attached the portion of the wiring diagram which shows the connection. The Malfunction Indicator Lamp is shown on the top left corner.

 

I have the speedhut gauges and I had them add a check engine light and LEDs for blinkers, the brake light, high beams ect.

 

In the case of these gauges the power is supplied by a single wire to the guage, then to turn the indicator lights on, they pull to ground (as you have stated), so it's super easy to wire them up. Makes it real easy to wire them since you don't have to provide power and ground to every light.

Edited December 6, 2010 by kjones

[VinhZXT]

I have been searching and have not found a thread that sufficiently covers this topic. I'd like for this thread to be the place where we share all of our knowledge on wiring for the LSX swap.

 

As part of my swap, we have been going through every single wire in the stock harness (1975 280z) and eliminating all the unnecessary wires as well as (more importantly) identifying all the wires that need to be retained for various reasons.

 

What we're finding is that in many cases when we trace a wire and look it up in the wiring diagrams there are several differences and incorrect information in the books! Granted they are 30 years old but there's quite a bit of stuff in the harness that has been quite surprising. (We even found wires for factory fog lights in the harness!! - never knew they were there!)

 

As part of our exercise, we're rewiring the dash in a few instances to accommodate several new items as well as to insure that the gauges operate properly. We also are eliminating the fusible links in favor of a maxi fuse block.

 

Most of the wiring, while overwhelming is pretty straightforward if you take your time. Some have probably not gone as far as we have, but anyway...

 

I have a few questions to start this topic off, then we'll begin to share in some subsequent posts on this topic the things we've learned.

 

Here's some questions that we're having some challenges with conflicting information in the wiring diagrams:

 

1. There is a black/white wire that comes off the ignition switch - It's labelled 3 different things in my books. We assume this used to go to the ground on the distributor, but it's also labelled "ALT". My assumption at this point is that it is no longer necessary. What have you guys done with it?

 

2. What wire are you using off the dashboard controls to actuate the magnetized clutch to turn the AC on? The JCI compressor is a single black wire... The GM compressor had a 3 wire harness.

 

3. The GM PCM wiring harness has an "AC" wire - We assume that this wire needs a signal (positive or negative??) so the PCM knows to increase the idle when the AC is on... Any suggestions? Or is this wire used for something else related to the AC?

 

4. Does the GM check engine light pull to ground or does it send 12V to light up the light?

 

5. What have you guys done for the backup light wiring? The connector is way too close to the tunnel and it will not plug in.

 

6. What have you guys done to make the stock voltage gauge work correctly since the "charge" light which was in the circuit to turn on the old Datsun alternator is no longer needed?

 

I will share all of the solutions to what we've already done on this post with pictures. It would be great if you guys could do the same as well.

 

Thanks for your insights - I think this post will be invaluable to future guys doing this swap.

 

 

Ken,

This is from the top of my head:

1. Anything coming off the ignition switch can not be ground. If I remember correctly the black/white is the ignition wire. Black/Yel is your starter wire. Both of these wires can be found at the White plug on the passenger side tunnel.

2. To actuate the AC compressor you just need a 12V source. You can use any simple push/latch or a regular toggle switch will work.

3. You can hook this wire to the wire that activate the AC.

4. Hook one side of the charge light to 12V ignition. The other side go to the output wire of the alternator. When the alternator dies it will pull to ground and will turn on the charge light.

GL

 

I had this stuff explained in one of my web page b4 but I can't seem to find it any more.

 

V.

Edited December 15, 2010 by VinhZXT

[kj280z]

Regarding the IAT Sensor...

 

The stock sensor looks like this:

 

I'd prefer welding a bung into my intake pipes so I need this style - Will this work with a 2002 PCM? http://www.diyautotu...ctor-p-116.html

It states that the specs are:

Temperature Ohms

48 degrees F 7000

87 degrees F 1930

146 degrees F 560

I have been unable to find similar specs for the stock IAT sensor to understand if the one at DIY is compatible

Edited December 16, 2010 by kjones

[kj280z]

Ken,

This is from the top of my head:

1. Anything coming off the ignition switch can not be ground. If I remember correctly the black/white is the ignition wire. Black/Yel is your starter wire. Both of these wires can be found at the White plug on the passenger side tunnel.

2. To actuate the AC compressor you just need a 12V source. You can use any simple push/latch or a regular toggle switch will work.

3. You can hook this wire to the wire that activate the AC.

4. Hook one side of the charge light to 12V ignition. The other side go to the output wire of the alternator. When the alternator dies it will pull to ground and will turn on the charge light.

GL

 

I had this stuff explained in one of my web page b4 but I can't seem to find it any more.

 

V.

 

Vin - Thanks! Regarding number 4, I'm wondering if I have to do something slightly different... The speedhut gauge faces required that I had to remove the charge light from the gauge. Is the charge light required to be in the circuit to turn the alternator on like it was to turn the Datsun alternator on?? Any ideas on wiring the gauge without the charge light?

 

On number 2 I am close to being able to test the blue wire to actuate the compressor using the stock dashboard controls - should work fine if the diagram is correct. I don't want to add any additional toggles if I don't have to...

[h4nsm0l3m4n]

Regarding the IAT Sensor...

 

The stock sensor looks like this:

 

I'd prefer welding a bung into my intake pipes so I need this style - Will this work with a 2002 PCM? http://www.diyautotu...ctor-p-116.html

It states that the specs are:

Temperature Ohms

48 degrees F 7000

87 degrees F 1930

146 degrees F 560

I have been unable to find similar specs for the stock IAT sensor to understand if the one at DIY is compatible

 

During my searching I discovered that people tend to use the GMC Syclone IAT sensors for this purpose. It threads into a 3/8 NPT bung which should be easy to get and weld in. In fact that sensor in your picture looks very similar...