1974 Engine Wiring Harness
Thread Starter
Racer
Joined: Jul 2013
Posts: 385
Likes: 3
From: Leesburg VA
1974 Engine Wiring Harness
OK, so my mechanic tells me that the engine wiring harness in my 1974 coupe 350/automatic is cracking and needs to be replaced.
My questions is:
Is this easy to do? Parts are reasonably cheap from the forum's vendors...~$150.
Do any of the wires in the harness need to be connected behind the dash? I would really rather not open up that can of worms at this time.
I do have the AIM, but it is not immediately clear to me which wiring connections belong to the engine wiring harness versus other harnesses.
I appreciate any guidance and advice you can provide.
John
My questions is:
Is this easy to do? Parts are reasonably cheap from the forum's vendors...~$150.
Do any of the wires in the harness need to be connected behind the dash? I would really rather not open up that can of worms at this time.
I do have the AIM, but it is not immediately clear to me which wiring connections belong to the engine wiring harness versus other harnesses.
I appreciate any guidance and advice you can provide.
John
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
...Is this easy to do?...
...Do any of the wires in the harness need to be connected behind the dash?...
...I do have the AIM, but it is not immediately clear to me which wiring connections belong to the engine wiring harness versus other harnesses....
These two harnesses plug together at the firewall and connect to the main dash harness.
Thread Starter
Racer
Joined: Jul 2013
Posts: 385
Likes: 3
From: Leesburg VA
Thanks for your response Easy Mike! I am planning to do the install myself, I am pretty mechanically inclined and have no problem with working on wiring in general.
My mechanic replaced the starter for me and noted that the insulation was cracking enough to begin exposing wires. He said it was only a matter of time before I started having problems due to water and corrosion. He taped the wires at the starter as best he could, but recommended changing the harness to ensure reliability. We are primarily focused on reliabilitiy and drivability issues at this point...the other harnesses may in fact be equally tired, but probably will not leave me stranded.
The car has left my wife and I stranded twice in the last 90 days...she was not pleased...hence my focus on making the car reliable.
John
My mechanic replaced the starter for me and noted that the insulation was cracking enough to begin exposing wires. He said it was only a matter of time before I started having problems due to water and corrosion. He taped the wires at the starter as best he could, but recommended changing the harness to ensure reliability. We are primarily focused on reliabilitiy and drivability issues at this point...the other harnesses may in fact be equally tired, but probably will not leave me stranded.
The car has left my wife and I stranded twice in the last 90 days...she was not pleased...hence my focus on making the car reliable.
John
Instructor
Joined: Oct 2005
Posts: 244
Likes: 1
From: Brighton Michigan
LudemJo,
I replaced the engine harness on my 74, and it's not that bad of a job. I think it looks more intimidating than it really appears to be. Your best tool will be patience. The harness attaches to the back of the fuse panel, start there and try to keep it organized. All the wires that go to their respective components are the same color in the new harness as in the original. So there's no need for confusion. Just go slow, take your time, and for God's sake do one wire at a time and work your way from the back of the fuse panel across to the passenger side and end at the starter. I found it easiest that when you take a wire off or out of a component add the respective wire from the new harness.
As a side note, when you get over to the seatbelt interlock relay on the passenger side firewall, note if the relay is bypassed (jumped) in any way, because you'll get done and the car won't start.
Alex
I replaced the engine harness on my 74, and it's not that bad of a job. I think it looks more intimidating than it really appears to be. Your best tool will be patience. The harness attaches to the back of the fuse panel, start there and try to keep it organized. All the wires that go to their respective components are the same color in the new harness as in the original. So there's no need for confusion. Just go slow, take your time, and for God's sake do one wire at a time and work your way from the back of the fuse panel across to the passenger side and end at the starter. I found it easiest that when you take a wire off or out of a component add the respective wire from the new harness.
As a side note, when you get over to the seatbelt interlock relay on the passenger side firewall, note if the relay is bypassed (jumped) in any way, because you'll get done and the car won't start.
Alex
Thread Starter
Racer
Joined: Jul 2013
Posts: 385
Likes: 3
From: Leesburg VA
1974 Engine Wiring Harness
Thanks Alex! That is just the kind of feedback I was looking for. Sounds like it is very doable in the garage at home. It will be nice to cross something off my list.
Thanks again, John
Thanks again, John
Race Director
Joined: Mar 2006
Posts: 14,112
Likes: 28
From: Florida
The wires going to the starter are usually the ones that crack etc. The rest of the harness could be perfectly OK.
Strip some of the cover back and check it. It's easy to cut out and replace a foot or so. Just crimp, solder and heat shrink and as good as new.
Strip some of the cover back and check it. It's easy to cut out and replace a foot or so. Just crimp, solder and heat shrink and as good as new.
Team Owner
Joined: Aug 1999
Posts: 30,995
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From: Ontario
This would be my first approach.
