Building a new Wiring Harness

[cebra]

I had a lot of issues, mainly a underhood ground of a hot wire that caused a small fire and melted the power wire through the fuse box and to the lights/ignition. With that said I am making a new harness for a LS swap, VSS, etc. I will post pics when I am done. Fuse Panel is from a 1992 Blazer.

Anyways, I may need some help along the way. First, I am converting my AC harness to heater only as I have none of the Ac stuff. Does a non-heat truck only use the resistor then out to blower and no blower relay like the AC system does? Also, does anyone know if Vintage Air uses the original AC harness if you get the “with factory AC” kit? Don’t wanna hack it up if the Vintage Air Kit uses all the existing AC harness. Thanks.

[cebra]

Progress report, I have the harness duplicated to the fuse panel and have added in wiring for tach, LS standalone harness, VSS, 3 gauge pod, wiper module, and radio...less the heater wiring. I still need to connect to the harness to the new fuse panel and the feed wires under the hood. I am going to go ahead and do the underhood wiring as well since I am going to put relays in for the headlights.

[cebra]

I am still trying to figure out the heater wiring since I am converting from AC harness to heater only (going with Vintage Air which I have confirmed doesn't use the original AC harness and I have no original AC components left). I have the resistor connector in this picture but I am not sure what to connect to blue/orange/yellow to duplicate the heater only harness. Anyone have a picture of the wires coming out of a heater resistor connector so I can figure out which of the AC resistor wire match to which heater resistor wires? I assume the AC/heater only resistors function the same?

[davepl]

Are you crimping your own ends? What kind of terminals are they, Packard?

[cebra]

No, I am clipping the connectors that are good and soldering them onto new wiring and replacing the ones that are burnt up (anything that had a constant 12V) or broken. I have also bought some Molex connectors to add in my own for wiring to wiring connections (mostly for the add-on stuff). I cut off the 92 Blazer fuse panel with a few inches of wire and will solder the wires onto this. New connectors get pretty dang expensive or I would replace them all.

[cebra]

I think I got the AC to heater only wiring figured out for anyone that is doing this:

From Fuse Panel: orange power to relay, brown power to switch
From Switch: yellow to resistor, lt blue to resistor, orange to relay
From Resistor: dk blue to relay
From Relay: black to ground, purple to blower

I guess the AC blower runs faster or draws more power so it needs the relay to perform as it should...not sure how true that is but above bypasses anti-dieseling relay and compressor switch.

[ManNamedJed]

You might consider these terminals instead of soldering each one. They crimp on, but then solder when you heat the heat shrink. There is a video on the additional info tab.

I use them for everything now.

https://www.wiringdepot.com/store/p/...onnectors.aspx

[RichardJ]

Why are you messing with the original fan resistors if you are installing Vintage Air?

Most wiring is included and you don't use any of the AC or heater wiring. Their web site has complete installation instructions that will also be included with the kit.

Save yourself a lot of head aches and don't refer to a wire by simply the color of the insulation. Especially with a 50 year old vehicle, but that applies to most all electrical equipment.

[cebra]

It will be a while before I put the vintage air in, I need to do NV3500 swap, LS swap, and then next will be the air;I want to run heat in the meantime so I am doing away with all the AC wiring and converting to a heater harness only to run the blower.

I am unsure how you would reference wires if you didn't use the color, if they were all black for example it would probably take 2x as long to figure out and explain. I am first referencing the schematic then tracing each wire end to end prior to soldering it in to make sure they match so if anything new has been placed into the harness or colors have changed I will catch it there.

Once complete, I will draw up a new schematic in case anyone just needs to replace their fuse panel. The 1992 Blazer fuse panel has a lot of extra spaces (ECM, TOCM, etc) but the fuses on the 71 match pretty well to the 92 as far as feed wires/outputs.

[cebra]

Originally Posted by ManNamedJed

You might consider these terminals instead of soldering each one. They crimp on, but then solder when you heat the heat shrink. There is a video on the additional info tab.

I use them for everything now.

https://www.wiringdepot.com/store/p/...onnectors.aspx

I have seen those, pretty cool but I am pretty far in and over 100 solders (3rd roll of solder, 3rd solder tip, 2nd roll of heat shrink) thus far so they would get pricey. My system is about 50% more wiring than the stock system due to LS wiring and the other add ons.

[cebra]

I have done all of the in cab wiring, the rear light harness, and am now working on finishing up the underhood harness. I lost count but maybe 150ish solders, a couple dozen rolls of wire, 3 spools of solder, 30 hours of soldering, and numb fingers but the end is in sight. I have done some FI motor swaps, auto to manual conversions, lots of fabrication and body work, engine rebuilds, etc....I would rate this as up there as far as difficulty. It takes a lot of research to understand what every wire does (not where it starts and ends but how it functions) and the internal workings of the new fuse panel. Hopefully there isn't too much to troubleshoot once installed as the harness is packed pretty tight.

[davepl]

I love redoing harnesses. Which is to say I don't love the work, really, but I love the result when every wire is the right length!

I've done a couple but would never attempt it with a box of terminals and connectors and a Packard style crimper! The only funky one is the top of the heater box, it's like a Christmas tree. Had to special order that, the rest are all vanilla shapes and sizes.

I'm not sure about soldering crimped connections. I do it myself in a "belt and suspenders" kind of way but it could weaken or harden the joint too, it's hard to say. I can't think of instances of the factory doing it though.

I think I've shared the whole anecdote of my Dad and the dealer chasing a random ALT light for years... turned out to be an incorrect assembly at the factory of the main bulkhead harness! So they're not always perfect even from new...

[cebra]

Side note, doing 20-30 solders back to back requires a pretty hot soldering gun. I have a Weller D550 and I love this thing, it is heavy and burns super hot. My father has had the same gun since the 70's and his is still working just fine.

[cebra]

Originally Posted by davepl

I love redoing harnesses. Which is to say I don't love the work, really, but I love the result when every wire is the right length!

I've done a couple but would never attempt it with a box of terminals and connectors and a Packard style crimper! The only funky one is the top of the heater box, it's like a Christmas tree. Had to special order that, the rest are all vanilla shapes and sizes.

I'm not sure about soldering crimped connections. I do it myself in a "belt and suspenders" kind of way but it could weaken or harden the joint too, it's hard to say. I can't think of instances of the factory doing it though.

I think I've shared the whole anecdote of my Dad and the dealer chasing a random ALT light for years... turned out to be an incorrect assembly at the factory of the main bulkhead harness! So they're not always perfect even from new...

Yeah, most of the connectors I have are new with pigtails since my power wire grounded out and melted a large portion of them. A lot of the smaller ones I was able to salvage (brake switch, park lamps, wiper, etc.) I cut off and left pigtails to solder it back to new wiring.

[cebra]

I got all my wiring in. Some things that did not work that now do are (1) aftermarket voltmeter (2) blower motor high woohoo (3) super bright headlights with the relay mod added (4) glovebox light. Now the only thing not working after install is the fuel gauge. I have the pink power feed to the right side (when looking at the back of the cluster and a wire direct from the fuel sender on the left. I am unsure if direct from the sender is correct as it used to go "through" the fuse panel but I thought this was a direct passthrough (i.e. not picking up ground or power); is this correct? Thanks.

See in pic below and the final harness before install. I will post some pics after install and if anyone wants information on how to wire in a new fuse panel from a junkyard vehicle I can provide some general how to.