Where to get Key hot source?

[D-n-Tyke]

I am installing a LS in my 1969 Suburban. One part I am hanging up on is the key hot signal I nees to send to my new "LS" fuse panel. I was planning on using the accessory signal off the key switch. Problem is when I looked at the operation of the stock ignition swith the accessory pin turns off when the key is in the crank position (and the solenoid pin ofcourse turns on). How do I keep the accessory pon hit while cranking?

How have you guys wired your swaps? Where did you pull you key hot signal from?

[Jason Banks]

I'm sure someone will chime in, but I'm pretty sure it's the "IGN UNFUSED" terminal on the fuse panel

[hewittca]

Yes, the ignition unfused is a good spot to get a keyed 12V source. I am in the middle of my LS swap and this is where I am getting mine. Keep in mind, this is basically just a 12V trigger signal for your LS fuse panel. The panel I have uses this signal to trigger the "key on" relays that supply 12V power from the battery to the appropriate items that require power only when the key is on.

[LS short box]

Just note on a LS swap you need a 12 volt key on/cranking and key running. Also you need a 12 volt signal constant to the ECM.

[D-n-Tyke]

Originally Posted by LS short box

Just note on a LS swap you need a 12 volt key on/cranking and key running. Also you need a 12 volt signal constant to the ECM.

Little confused on what you mean by "you need a 12 volt key on/cranking and key running".

I thought I only needed 3 external wires to my LS harness.
(1) 12V Key Hot (This needs to be hot when the key is on AND while the engine is cranking)
(2) 12V Battery Hot (This is directly to the battery, Hot at all times)
(3) Fuel Pump power out of the harness to power the fuel Pump.

Optional external wires
(4) Trigger signal wire(s) for electric fans
(5) TCC Lockup/Brake Signal

[LS short box]

Sorry I maybe didn't say it very well.
You are correct on 1,2 and 3.
Two ways to do the fan or fans. Signal from the ECM or bung in the radiator with a temp sensor from a kit from Painless Wiring. I've used both with no problems. If you use the ECM to control the fan/fans you can fine tune the on/off temps to your application.
TCC? Not knowing what year LS you are using the earlier year LS (24 tooth reluctor crank wheel) needs an open from the brake switch to release the lockup. I've used a 2002 Camaro brake lite switch. It has two set of terminals on the switch. One open and one closed when you press the brake pedal.
Later LS ECM's need a closed switch sending a 12 volt signal to the ECM to release the lockup. On my 80 Camaro project I just spliced into the stock brake light wiring/switch for a 12 volt signal when you pressed the brake pedal. It's a 2012 6.2/4L60E combo 58 tooth reluctor crank.

[D-n-Tyke]

Originally Posted by LS short box

Sorry I maybe didn't say it very well.
You are correct on 1,2 and 3.
Two ways to do the fan or fans. Signal from the ECM or bung in the radiator with a temp sensor from a kit from Painless Wiring. I've used both with no problems. If you use the ECM to control the fan/fans you can fine tune the on/off temps to your application.
TCC? Not knowing what year LS you are using the earlier year LS (24 tooth reluctor crank wheel) needs an open from the brake switch to release the lockup. I've used a 2002 Camaro brake lite switch. It has two set of terminals on the switch. One open and one closed when you press the brake pedal.
Later LS ECM's need a closed switch sending a 12 volt signal to the ECM to release the lockup. On my 80 Camaro project I just spliced into the stock brake light wiring/switch for a 12 volt signal when you pressed the brake pedal. It's a 2012 6.2/4L60E combo 58 tooth reluctor crank.

Welp shoot. Now you got me a little worked on the TCC. I built my fuse/relay panel so that the TCC relay is normally closed (supplying the ECM 12V) and then when I hit the brakes the relay opens and interrupts the 12V going to the ECM. Everything I read I thought that was how it was supposed to be wired up. Is this not correct?

Donor is a 2004 Suburban 6.0/4L80

[LS short box]

An 04 LS should be a 24 tooth crank wheel so I think you got it right.
But a stock C10 brake light switch only has one set of prongs? and when you step on the brake the circuit is closed and the brake lights go on.
Using the 02 Camaro brake light switch (some use 88 Monte Carlo) has two sets of prongs. One set the closes the circuit and one set that opens the circuit. You can check to see which is which with a meter.
It's OK to use a relay but I never have and never had a failure.

[D-n-Tyke]

Originally Posted by LS short box

An 04 LS should be a 24 tooth crank wheel so I think you got it right.
But a stock C10 brake light switch only has one set of prongs? and when you step on the brake the circuit is closed and the brake lights go on.
Using the 02 Camaro brake light switch (some use 88 Monte Carlo) has two sets of prongs. One set the closes the circuit and one set that opens the circuit. You can check to see which is which with a meter.
It's OK to use a relay but I never have and never had a failure.

Got it. Yeah, if I would have known about the later model bracket light switch, with both switch styles, I would have gone that route. Oh well, already wired and, fingers crossed, it will work as wired.

[clay68c10]

I used the coil power wire for the ignition hot.