81-86 chevy truck wiring harness 2nd opinion - Hot Rod Forum : Hotrodders Bulletin Board
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Old 08-01-2011, 09:42 AM
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81-86 chevy truck wiring harness 2nd opinion

Classic Industries has a reproduction engine wiring harness for years upto a 1981 Chevy truck. Apparently these harnesses are based upon OEM schematics. I have a 1986 Chevy truck and the Classic Industries rep. said the 1981 harness will not work. Since the two vehicles are otherwise identical, I have a hard time believing it won't work. I have no way of comparing a 1981 and 1986 chevy truck wiring harness for a carbureted 305, myself. Can anyone provide further insight as to the compatibility the 81 wiring harness for a 86 chevy truck. Would the adaption of the 81 wiring harness to the 86 truck be easier than Painless Wiring?

Thanks.

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Old 08-01-2011, 07:29 PM
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This depends what you are trying to do. Rewire the entire truck? Or what?
1981 was a transition year for the engine controls. Ignition system advance control was changed to computer control and other engine changes.
The basic chassis wiring remained the same, such as lighting.
What are you trying to do?

vicrod
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Old 08-01-2011, 08:43 PM
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I took an 81 apart not too long ago.
Seems to me that the "BASIC" harness is just that----BASIC
All the cruise, PW, PL, AC, engine management, etc. were all add on harnesses.

I may be able to get that harness out and have a closer look sometime this week.

Anything you would like me to look for??

I do know there are 3 connectors at the bulkhead.
Headlight harness
Engine--Electrical feed harness
Taillamp harness
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Old 08-02-2011, 10:44 AM
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I am doing a restoration and I would like to replace just the engine wiring harness for my 86 GMC Wrangler. The intention is to keep it as stock as possible. The front and rear light wiring look good as does the interior dash wiring.

I do not know what the differences are in the engine bay to suggest looking for something in particular, but maybe a photo of what a 81 engine harness looks like may help.

Thanks.
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Old 08-02-2011, 03:10 PM
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I attached the '81 and the '86 schematics.
The '81 did not have an ECM while the '86 does.
It should be very simple to isolate (remove) the '86 engine controls and wiring and use the dist. and module from the '81. No harness needed.
I believe the '81 did not have any electronic controls for the carb. so you could use an HEI dist. from '75 to '80. They are self contained with centrifugal and vacuum advance.

vicrod
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File Type: pdf '86 GMC truck wiring .pdf (396.6 KB, 588 views)
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Old 08-02-2011, 08:50 PM
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I am by no means electronically inclined but having looked at the schematics it seems the wiring portion I am interested in replacing are similar. That is the portion of wiring involving the battery, starter, alternator and especially the fusible link, as well as the wiring for the choke. You see my fusible link, which is attached to the firewall, has blown and the wiring to the choke must be bad as when I wiggle it the choke light goes out and idle changes. I am hopeing I can change just the portions of wiring that are bad instead of having to replace the entire harness. It seems practically impossible to find an orginal harness for that year.
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Old 08-03-2011, 12:10 PM
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I had my wiring harness burn up a few months back and ran new wires from the firewall including soldering new fusible links. It really isn't that difficult to do and it gave peace of mind knowing that all of the wiring is now good.
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Old 08-03-2011, 11:00 PM
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When you said you ran new wires from the firewall, were you able to attach and run those wires right from the fuse box? In other words is it possible to detach a wire from the fuse box and insert a new one in its place or do I have to cut the wire after it leaves the fuse box and solder a new wire onto it? However time consuming, it would be much easier for me if I could replace individual wires as needed.

thanks.
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Old 08-04-2011, 09:06 AM
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Yes, you can pull the backside of the fuse panel off from the firewall side. there is a bolt in the center holding it on. Once it is off you can find the wire you need to replace. To get the wire to release from the panel you must squeeze the base of the terminal together and it will then slide out. If your terminals are like mine they were packard blade terminals. I mention this because there were only to places that I found that carried them. One is Napa and they had to order them for me and the other was clipsandfasteners.com.

One other thing I would mention is that Napa had the best deal of the fusible link. I needed to solder in 4 of them so I bought a roll. Also, if you didn't already know when choosing fusible link size you need to go 2 size smaller than the gauge of wire you are using. For example a 10 GA wire would require the 14 GA fusible link.

It is time consuming, but I'll tell you its amazing how much better things work with solid fresh connections and wiring.
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Old 08-05-2011, 11:05 PM
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Thanks for the information everyone. I am going to try and replace individual wires as jmichaelre suggested.

Cheers Hotrodders!
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Old 09-26-2012, 11:33 AM
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hay ? what if u have an 81 chevy with a 6 clinder and swap it out with a 305 is the engine wiring harness the same an amaricn auto wire rep. said the 305 harness will not work gas mine had the 6 clinder and the dash harness is differnt I have a hard time believing that gm wold use differnt ones what u think
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Old 09-26-2012, 12:39 PM
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There are other differences in the main harness. The 81 has the wiper switch on the dash, 86 is on the column in the turn signal lever. Also, not all 86 trucks have an ECU. Most 49 state trucks do not, and all above 8600 GVW do not. There ARE some small electronic modules, like the A.I.R. control box on the 86. How these affect the main harness I'm not sure.
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