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  #1  
Old 10-27-2019, 08:10 AM
ClassicQueen ClassicQueen is offline
230 Tornado
 
Join Date: Sep 28, 2019
Location: Fitchburg, MA
Posts: 17
75 j20 wiring issues

Hi, this is my third attempt at posting
I recently acquired at 75 J20 AMC 360. Truck runs I have not drove it due to concerns with wiring. Ignition button cranks truck without key. Fuel pump runs only when key is in the ON position or all the way towards driver. Gauges do no appear to work except for oil pressure gauge. Neither wiper or lights work. There are parking lights missing, which i could probably source. The battery cannot be kept connected as it gets drained. Voltage regulator is disconnected and appears to have been decommissioned for a long time.
The way things look, I might need to replace all wiring, there are plenty of cut off wires in the cabin as well.
https://photos.app.goo.gl/ZGGifavePd4xjpWPA
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Old 10-27-2019, 10:34 AM
joe joe is offline
 
Join Date: Apr 28, 2000
Location: PNWet, USA
Posts: 22,392
Ouch! Rather than trying to patch/save whatcha got... I'd punt. Get a paper copy of the original 75 TSM and wiring diagram and just dump the butchered orig harness. EZWire and Painless offer a generic truck harness. Both are good quality, easy to install, labeled and include a new fuse box. The orig 75 FSJ harness wasn't great in the first place so trying to save it after DSPO butchering IMHO is futile.
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Old 10-27-2019, 11:31 AM
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letank letank is offline
AMC 4 OH! 1
 
Join Date: Jun 03, 2002
Location: San Francisco
Posts: 3,886
as Joe said, it is a bit of a challenge to redo a wiring system, because one need to understand how the original designers laid out the wires, which is always a puzzle.


the coil pictures has a ceramic resistor to bypass the resistor wire that is part of the original wire loom that runs on the passenger side of the valve cover. Usually those wires get cooked because they are too close to the exhaust manifold.


Starts with the cranking/ignition/charging system to keep it simple



Being a 75 you may still have the prestolite ignition distributor, which has 2 white plastic vacuum canisters on the distributor, those have a bad reputation and where used for years 75-77 or about. One user claim that they can be refurbished or kept up for little care, most people move to the post 78 system called the duraspark


as for charging, time to do the ammeter bypass


EDIT: do not forget to remove that coil to battery wire when you turn off the engine, otherwise the coil will still be powered with a potential risk of fire


EDIT2: for any aftermarket wiring such as painless, you still need to reuse your original wire plugs at the firewall
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74 wag, 349Kmiles on original ticker/trany, except for the rust. Will it make it to the next get together without a rebuilt? Status: needs a new body.
85 Gwag, 226 Kmiles. $250 FSJ test lab since 02, that refuses to give up but still leaks.

See Ouray 2013, Engine bits and Fuel and brake lines, and Body work

Last edited by letank : 10-27-2019 at 01:00 PM.
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Old 10-27-2019, 01:05 PM
ClassicQueen ClassicQueen is offline
230 Tornado
 
Join Date: Sep 28, 2019
Location: Fitchburg, MA
Posts: 17
ok, is it better to get a harness kit or an original harness?


Quote:
Originally Posted by letank
as Joe said, it is a bit of a challenge to redo a wiring system, because one need to understand how the original designers laid out the wires, which is always a puzzle.


the coil pictures has a ceramic resistor to bypass the resistor wire that is part of the original wire loom that runs on the passenger side of the valve cover. Usually those wires get cooked because they are too close to the exhaust manifold.


Starts with the cranking/ignition/charging system to keep it simple



Being a 75 you may still have the prestolite ignition distributor, which has 2 white plastic vacuum canisters on the distributor, those have a bad reputation and where used for years 75-77 or about. One user claim that they can be refurbished or kept up for little care, most people move to the post 78 system called the duraspark


as for charging, time to do the ammeter bypass
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  #5  
Old 10-30-2019, 09:45 AM
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tgreese tgreese is offline
 
Join Date: May 29, 2003
Location: Medford MA USA
Posts: 11,159
Quote:
Originally Posted by ClassicQueen
ok, is it better to get a harness kit or an original harness?
Better depends on you. Any hot rod harness will require that you route and terminate the circuits and understand (to some degree) what you are doing. It will be different from the factory wiring, so you will need to rely on your notes and the instructions from the kit to diagnose and repair any issues with the new wiring.

The factory harness can be put back exactly like it came from the factory, and the factory wiring diagram can be used for any subsequent diagnosis and repair.

Personally I would fix the factory wiring unless there had been a fire. You can straighten out the mess if you go one circuit at a time and repair the PO's sloppy changes.

Or, get the harness from fsj454 and install that. Supposedly Zach at Z&M Jeeps (?) has replacement harnesses for these vehicles. Might be worth looking into. http://www.ifsja.org/forums/vb/showthread.php?t=187862

Here's some help with harness repair: https://www.jeepforum.com/forum/f8/b...arted-1340134/
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  #6  
Old 11-12-2019, 02:42 PM
ClassicQueen ClassicQueen is offline
230 Tornado
 
Join Date: Sep 28, 2019
Location: Fitchburg, MA
Posts: 17
Where could I get a wiring diagram for the the year? I looked in the web and wasn
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  #7  
Old 10-27-2019, 11:37 AM
fsj454 fsj454 is offline
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Location: new bedford ma.
Posts: 471
cabin harness

I have a good harness for 1975 glass fuses and steering column
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1982 cherokee nt. 454. nv4500 .205. dana 60 f+r. twin stick.hydroboost.hydrolic clutch.rock ram.traction bar.warn 12000 winch.4 wheel disc.flip kit.soa.high steer.cross over steer.4.56 detroit locker.35 spline rear alloy axles. 37s .1990 grand wagoneer aka trusty rusty
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Old 10-27-2019, 01:07 PM
ClassicQueen ClassicQueen is offline
230 Tornado
 
Join Date: Sep 28, 2019
Location: Fitchburg, MA
Posts: 17
I'm definitely interested on column mine is pretty beat.
Quote:
Originally Posted by fsj454
I have a good harness for 1975 glass fuses and steering column
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Old 10-27-2019, 05:01 PM
fsj454 fsj454 is offline
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Location: new bedford ma.
Posts: 471
transmission

What type of transmission do you have
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1982 cherokee nt. 454. nv4500 .205. dana 60 f+r. twin stick.hydroboost.hydrolic clutch.rock ram.traction bar.warn 12000 winch.4 wheel disc.flip kit.soa.high steer.cross over steer.4.56 detroit locker.35 spline rear alloy axles. 37s .1990 grand wagoneer aka trusty rusty
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  #10  
Old 10-28-2019, 04:20 PM
ClassicQueen ClassicQueen is offline
230 Tornado
 
Join Date: Sep 28, 2019
Location: Fitchburg, MA
Posts: 17
Not sure of type but it is automatic

Quote:
Originally Posted by fsj454
What type of transmission do you have
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