"Simple" LS Wiring Questions

[JohnIL]

I'm about 80% of the way through wiring the 5.3L in my son's '83 El Camino and I have a couple of questions for the experts. I'm working with a reworked LS harness and ECM, but unfortunately, the company that sold me the engine and the harness went out of business during the pandemic. The harness is pretty well labeled, but I'm missing some details.

1. There is a wire in the harness labeled "Brake Switch". Does anyone know the purpose of this wire? And, where does it get connected to the brake switch? My first thought was that it is for cruise control, but this is a drive-by-cable engine, so cruise control will have to be aftermarket. Any ideas? Do I tie this into the brake light positive wire or does it need to tap into a specific terminal on the brake switch?

2. In my build thread, member 64nailhead mentioned that I'll need to hookup the brown idiot light wire to the LS alternator. On the small block alternator, it's part of the white flat plug. Where does it go on the LS alternator? The new engine harness has a flat plug, Does it tie into this plug somewhere?

3. The simplest wire in the harness may turn out to be the most difficult to hook up. There is supposed to be a pink wire that feeds power to the ignition system when the key is on. The challenge is, the El Camino came from the factory with an Olds 350 diesel. There is no pink wire in the factory harness. Any suggestions on where to find good keyed 12V power? Is there something else in the factory harness or will I need to tap into the factory fuse box somewhere?

Thanks for any suggestions.

John

 

[ELCAM]

#3. There should be a wire that went to a solenoid on the injector pump it provides the same function as the distributor wire on the gas engine.

 

[64nailhead]

I need a couple of pics to give info that is accurate for the alternator that you have.

The brake wire should be there for both cruise control and torque converter lockup function in the ECU - the issue I have is that I don't know if the factory ECU needs a 12v+ input or a ground switched input. Hopefully Jake, Mike or someone in the know about factory ECU's chimes in. If no one does, then you can easily test it while driving with some minor apparatus setup.

Regarding the necessary pink wire, this shouldn't be too difficult to determine. There should be a pink wire in the column (ignition wiring) that is a 10 or 12 gauge wire. I would find it hard to believe that a Diesel would be different inside the car from a gas car.

 

[L92 OLDS]

I'm about 80% of the way through wiring the 5.3L in my son's '83 El Camino and I have a couple of questions for the experts. I'm working with a reworked LS harness and ECM, but unfortunately, the company that sold me the engine and the harness went out of business during the pandemic. The harness is pretty well labeled, but I'm missing some details.

1. There is a wire in the harness labeled "Brake Switch". Does anyone know the purpose of this wire? And, where does it get connected to the brake switch? My first thought was that it is for cruise control, but this is a drive-by-cable engine, so cruise control will have to be aftermarket. Any ideas? Do I tie this into the brake light positive wire or does it need to tap into a specific terminal on the brake switch?

2. In my build thread, member 64nailhead mentioned that I'll need to hookup the brown idiot light wire to the LS alternator. On the small block alternator, it's part of the white flat plug. Where does it go on the LS alternator? The new engine harness has a flat plug, Does it tie into this plug somewhere?

3. The simplest wire in the harness may turn out to be the most difficult to hook up. There is supposed to be a pink wire that feeds power to the ignition system when the key is on. The challenge is, the El Camino came from the factory with an Olds 350 diesel. There is no pink wire in the factory harness. Any suggestions on where to find good keyed 12V power? Is there something else in the factory harness or will I need to tap into the factory fuse box somewhere?

Thanks for any suggestions.

John

This will answer all of your questions. Were you aware of this site?

Wiring Harness Information

 

[Texas82GP]

My 82 GP diesel had the pink wire in it. My favorite bodge on the swap was how the P.O. tapped off of hot to the coil with a scotch lock for the choke. Good stuff.

 

[JohnIL]

#3. There should be a wire that went to a solenoid on the injector pump it provides the same function as the distributor wire on the gas engine.

Thanks for this. Once I get the battery connected, I'll have to do some more exploring in the factory harness.

 

[JohnIL]

My 82 GP diesel had the pink wire in it. My favorite bodge on the swap was how the P.O. tapped off of hot to the coil with a scotch lock for the choke. Good stuff.

I'm guessing this is the same wire ElCam mentioned. Thanks for confirming. Now, I just hope I can identify it.

 

[JohnIL]

This will answer all of your questions. Were you aware of this site?

Wiring Harness Information

Thanks for the link. I haven't see that site before. It's full of useful wiring information.

 

[81cutlass]

Yeah LT1 swap has what you need for what you need to do with the brake switch wire. It is used to disable the cruise and unlock the torque converter. Memory says it's normally 12v and shuts off when you tap the brakes but I'd check.

Your car might not have a brake switch that is normally closed, open on brake pedal if it's not a factory cruise car. You can tap off that cruise input on the brake switch for that wire if you do have a cruise car.

There is a second wire titled 'cmhs' or something for the 3rd brake light. For cruise to work it needs to see the 12V signal on the brake switch and resistance/ground across that wire. That's a goofy one what in the factory truck if you put LED 3rd brake light bulb or the bulb burns out the cruise shuts off. You can tap into the OEM G body brake light wiring for that if you want your cruise to work but may need to add resistors. 4kohm seems right???

And cruise on a DBW is easy if it's a gen 3. A stock G body 83+ cruise switch wiring will connect directly into the 02-07 harness and it just works. The only way to not have cruise on a gen 3 dbw is to have flex fuel, t56 (me 🙁 ) because the OS doesn't exist.

 

[JohnIL]

I need a couple of pics to give info that is accurate for the alternator that you have.

The brake wire should be there for both cruise control and torque converter lockup function in the ECU - the issue I have is that I don't know if the factory ECU needs a 12v+ input or a ground switched input. Hopefully Jake, Mike or someone in the know about factory ECU's chimes in. If no one does, then you can easily test it while driving with some minor apparatus setup.

Regarding the necessary pink wire, this shouldn't be too difficult to determine. There should be a pink wire in the column (ignition wiring) that is a 10 or 12 gauge wire. I would find it hard to believe that a Diesel would be different inside the car from a gas car.

64nailhead,
See the attached picture. The brown wire is the one labeled "IND LIGHT". It's part of the white two terminal plug that plugs into the alternator case. Any idea how/if this should attach to the LS alternator?

Thanks.
John