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Post Info TOPIC: Remaking the engine wiring harness. SAE wire, where to buy local?


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Remaking the engine wiring harness. SAE wire, where to buy local?


I'm going to attempt to make new underhood wiring harnesses, although they still worked at the time of removal, they have become very hard and inflexible with some insulation showing cracking. They also are filthy and look like crap. The connector plugs still are in decent shape, and the pins should come out and be re-usable. I have two complete harnesses to work with, so I'm lucky there. I'll be eliminating the regulator (using a internal reg'd 12SI alt.) and the horn relay, and will be adding Bosch type relays to cover the Horn and Headlights.

A good post describing the job in detail will follow. Most 40 year old harnesses are probably in tough shape and in need of a sprucing up. So someone might value the info.

I'll need some 10-20 Ga. wire and fusible links to start with.

Looking on the net for wire tells me to get good quality wire is going to cost some bucks. Replacement harnesses can be as much as $450, and I can see why! As far as I know you can't just source this high temp. SAE J1128 wire at your local NAPA or the like. The lugs, wrap and misc. I can get here. I have the relays.

Anyone here know of somewhere in Ontario to buy autowire? Any thoughts on the project? Electrical experts?


From the net,

Recommended by the SAE for underhood use.


SAE J1128 Wire Insulation Types:


TXL
, Light Insulation Thickness, 18 to 12 ga. wire
GXL, Medium Insulation Thickness, 18 to 12 ga. wire
SXL, Heavy Insulation, 8 and 10 ga. wire
SGX, Heavy Insulation, 6 gau. to 1/0 ga. wire


This a much tougher and more temperature resistant wire that the 85° and 105° wires, and is generally not available from retail auto supply stores. This wire is insulated with crosslinked polyethylene, (XLPE) which is what gives it the 125° C. temperature rating.

It is a much better insulation than the polyvinyl Chloride (PVC ) wire sold in your local retail stores. XLPE has a higher temperature rating and a much better solvent resistance, and is mechanically much tougher.

It is what the automakers use when they manufacture your car or motorcycle.
The cost is generally only about 20% more than the cost of the other wires, which makes it a real bargain.

This wire is rated under SAE J1128 for temperature up to +125°C or 257°F. For general circuit wiring.  

Really pretty straightforward. I'd like to see one from a modern car!

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MC.




-- Edited by cdnpont at 11:06, 2009-02-07

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65 Laurentian post, 67 Grande Parisienne 4 door HT. 
 


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When I dropped the big block into my 70 2+2 three years ago, I needed to make up a new engine harness.  I had a number of harnesses to work with.  I sourced the brass connectors from NAPA, and most of the wire from the local auto parts place (Auto Value in Calgary).  They had a good selection of blue, green, yellow, etc wires, in small packets and in rolls.  I only re-used the heavy guage purple wire the goes to the starter solenoid, and the resistive wire with a braided coating for the coil.  On the big blocks, they also used a braided wire from the coil to the starter solenoid (non-resistive) and I got that from a a place that sells parts for restoring old lamps, etc.  The big blocks also used a braided wire for the last foot or so on heavy guage purple wire, I got that from a place that services kitchen appliances. 

On my way to POCI in California 3 years ago, we got caught in traffic by a fatality accident just outside Las Vegas, and inched along for 1/2 hour.  Outside temp was 115 F, and I'm sure the underhood temperature was higher than you'll ever see, and the wires were not effected at all.

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70 2+2 hardtop
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Thanks Clint,

You make a good point about underhood temperatures. Maybe I'm being overly concerned. If the standard wire can take it during your desert test, it certainly could survive here beside a SB.
Indeed, it would make it way easier (and cheaper) to use the regular type wire. We have a whole rack at work of every colour and Ga imaginable.
Good to know some of the pins are avail. at napa.
I'm going with a HEI, so I could probably eliminate the white braided type to the coil. Or is a certain resistance needed still? Why does that double wire to the coil have the braided insulation?

What did you use to wrap your harness?

Mark

-- Edited by cdnpont at 10:52, 2009-02-07

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A Poncho Legend!

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On a side note Mark, that asbestos type (not asbestos, I'm sure) wire loom is still available. If heat is a concern you could use that in the necessary areas. I just bought some recently and it looks identical to the OEM stuff from the 60's. In case you don't know the stuff I mean it's what is usually covering the oil pressure sending unit wire.

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars



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mark, you need a full 12v to the HEI. change the resistor wire to the bulkhead with 12ga and remove the other end that goes to the starter completely.

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Thanks Dave,

I knew there was somthing that needed to be done for HEI.
I'll incorporate the change into the new harness.

Now I know how to spot a resistance wire, it's usually braided...because it gets...hot. Doh!
That Coil 20 Ga. white resistance wire goes to the bulkhead connector and becomes a 12 Pink, picking up power from the fuse buss. A 12 red splices off the Pink and travels to the Ign switch.

Yes, I've seen that insulated loom Carl. There's a guy on ebay selling as "old school" wire insulation. I'll need some. Thanks.

Keep the tips coming!

Cheers, Mark



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Also, you do know that all those terminal ends are readily available still? I am constantly redoing harnesses and it comes in handy having those terminals around for the male and female half of the connectors.

I was at a friends house the other night and he had no idea. He was saving them off old harnesses, opening them up and soldering them onto new wires. What a time consuming pain in the you-know-what!

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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars



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69 belair is correct, with the HEI you don't need the resistive wire.  The resistive wire (braided) was used in place of the old ballast resistors that were on the firewall, they reduced the voltage to improve breaker point life.  The wire from the starter (usually yellow, sometimes white) to the coil provides a full 12V during engine cranking.

Most of the wire I got from Auto Value was "Pico" namebrand.  I've also seen it at many electronic supply places.

NAPA part #'s for the terminals are:
784490   GM 56 Series Male Terminal 18-14 Ga, 5 pieces.
784491   GM 56 Series Female Terminal 18-14 Ga, 5 pieces.
The last time I checked at my local NAPA, I couldn't find the pins.  I got more at my local AC Delco dealer, but they were grey colored not brass.  Color really doesn't matter as they're buried within the plastic cover.

The wires I had the most difficulty finding were the ones with the tracer (black with yellow stripe, etc).  They're not usually used on the engine itself, but the wiper motor sometimes has one or two.  I also re-used the wire that goes to the brake switch.

To wrap the wire, I used the 1" or 3/4' wide non adhesive wrap that you can buy at Auto restoration shops.  Places like Year One and Classic Industries sell it, and your local Auto restoration shop should have it.  Don't use electrical tape as the adhesive will give way over time.  (I used electrical tape just to hold the harness together, but wrapped it with non adhesive tape)

-- Edited by seventy2plus2 at 11:38, 2009-02-07

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70 2+2 convertible
70 2+2 hardtop
70 Parisienne hardtop
72 GMC Sierra

 

 



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Really good tips guys,  I'm tackling this stuff right now myself.  I had hopefully bought a repro firewall forward harness from Classic for a 66 chev with 396 and AC (No gauges) but it is not even close to working (especially the AC stuff)  I'm guess I'll rob what I can from it in the way of new wires/ends and rebuild my old harness which is is the usual shape for a 45 year old set of wires.  Anybody know an easier way?

ken

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ken from northern Alberta

38 Willys pickup electric

39 Buick (327 with 700 r4)

66 Beaumont 4 door hardtop

69 Chevy CST pickup

1976 GMC 23'  motorhome

1994 Impala SS (temporary, according to my wife)

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