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I dropped a 350 in the old girl, and the shop removed most all of the old wiring from the I4. They also pared back the wiring for the Back up light switch on the Tranny, and the 4x4 engaged switches on the np-231 and dana front axle. I've tried finding prints that tell me what the color codes are for these, and the best I could find was black and yellow for the 4x4. Found one wire, and when 12 vdc applied, nothing. no indicator, nothing. Anyone have any ideas?
 

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Welcome to the Forum adk_man,

Find a post by Got it at last. In his signature there's a free link to several Factory Service manuals and a couple Factory Parts Manuals.
Open that link and click on the manual that you need.

The Jeep Factory Service manuals won't help much with your SBC, but you should find the answers your back up lights and your 4X4 light.

The 1987 and perhaps as new as 1990 YJs have a vacuum switch on the firewall that illuminates the 4X4 light. It's near the battery,
On 1991 and newer YJ D30 axles, the switch is on the Central Axle Disconnect (CAD). That should help you find the wiring for your 4X4 light, depending on what year your Wrangler is.

Good Luck, L.M.
 

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Don't just go around and apply 12V to any wire that you don't know where it's going to.
You can use a simple 12V bulb, one side to 12V plus, the other to the Yellow wire and the the black to ground. If you switch into 4 Wheel, HI or LO, the bulb should light up. Of course only when the CAD is engaged and the wires hooked up to the switch.
 
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'89 YJ 4.2 with MC-2150 Carb & HEI, 2-1/2" Ex. AX-15, NP231 SYE, Adams shafts, F&R ARB, 3
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So do you not have back up lights, 4x4 indicator or both?
Did you swap trannys? Manual to auto?

You should have a wide flat connector heading to the undercarriage just by the heater hose outlets on the firewall that connect to the cad, backup neutral safety switch etc.

Factory Service Manuals are below in dropbox link in my signature, open up your year and find your wiring diagram. You should be able to find the wires off the firewall loom and work back to accessories from there.

Also agree with Manny on not poking 12v in places where it don't belong unless you have a big box of spare fuses.
 
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