How to unhook main harness
Thread Starter
Drifting
Joined: Jan 2003
Posts: 1,894
Likes: 3
From: Reading PA.
How to unhook main harness
Can someone tell me how to unhook the main wiring harness where it hooks in at the firewall on a 84 vette? Does it unhook from inside the car under the dash or on the outside at the firewall? I didn't see any clips holding it on at the firewall. THANKS FOR THE HELP Pipe
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
I have never done it, so proceed with caution. I believe that the front lamp harness plugs into the engine wiring harness at the firewall, om the engine side. I also believe that either before, or maybe only after you unplug the front wiring harness, there is a small bolt that removes from the engine side of the firewall. Once the bolt is backed out, it allows you to unplug the engine side of the harness(es) from the socket. Then, I believe there are a couple of screws holding the socket to the firewall. I think I have given you a place to start, but be sure of what you find before you damage it. Good Luck.
RACE ON!!!
RACE ON!!!
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
Originally Posted by bogus
If the 1984 harness is anything like the 1987 harness I am trying to sort out, good luck. It's a pig... and the wiring runs back to the ECM, DIC and IP.
There is no connector. Sorry.
There is no connector. Sorry.
RACE ON!!!
PS. DIC = Driver Information Center. IP = Instrument Panel.
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
I have done this 2-3 times, If it is like the 85, it is like CFI said, there is a bolt in between the upper and lower connector, take the bolt out and then the upper and lower connector can be removed, if I recall correctly, thee are clips on the side of the connector.
The two connectors are wrapped into one thick wad of cables, but they can be separated when unwrapped.
The two connectors are wrapped into one thick wad of cables, but they can be separated when unwrapped.
Thread Starter
Drifting
Joined: Jan 2003
Posts: 1,894
Likes: 3
From: Reading PA.
Thanks guy's i'll look for the bolt tomorrow. It's gotta be small not much room between the two harness's What a wad of wires snakey mess. THANKS AGAIN AND I"LL LET YA KNOW HOW I MAKE OUT Pipe
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Race Director
Joined: Feb 1999
Posts: 12,772
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From: Indianapolis IN
Originally Posted by pipe
Thanks guy's i'll look for the bolt tomorrow. It's gotta be small not much room between the two harness's What a wad of wires snakey mess. THANKS AGAIN AND I"LL LET YA KNOW HOW I MAKE OUT Pipe
Team Owner
Joined: Aug 2000
Posts: 40,156
Likes: 45
From: San Pedro CA
Originally Posted by CFI-EFI
Not at the firewall? The parts book lists an engine wiring harness and a body, main wiring harness. Why would they need both if they were all one?
RACE ON!!!
PS. DIC = Driver Information Center. IP = Instrument Panel.
RACE ON!!!
PS. DIC = Driver Information Center. IP = Instrument Panel.
Drifting
Joined: May 2005
Posts: 1,302
Likes: 1
From: Tomahawk WI
The 1987 has a connector for the lights and stuff, but the main engine harness has no connectors... the climate stuff is part of that bundle.
Same on the 86?
Race Director
Joined: Feb 1999
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From: Indianapolis IN
Originally Posted by AZC4Guy
So the wiring just runs straight thru the firewall to the ecm?
Same on the 86?
Same on the 86?
The ECM harness indeed runs thru the firewall, there is a round or a rectangular grommet that has a bracket around it that bolts to the firewall. This harness contains the fuel injectors and essentially most all of the engine management connectors.
Remove the bracket and pull the harness through, but this ECM harness is wire wrapped together with the two lengths of wiring that go thru the firewall behind the battery. They are individual harness's but they are all wrapped together.
As Bogus stated, I believe that the harness's behind the battery are for the headlights and turn signals etc, and the other is for the dash gauge info, AC etc.
I unwrapped all of the wires and made them individual harness's. With the distributor in, removal of this harness is a nightmare, you may want to pull the distributor if you feel comfortable with doing this.
Drifting
Joined: May 2005
Posts: 1,302
Likes: 1
From: Tomahawk WI
LD
Looks like mine is behind the passenger side valve cover and rectangular. I'm going to have to take the valve cover off to get a good look at this. Do you think I'm looking at what we are discussing?
Steve
Looks like mine is behind the passenger side valve cover and rectangular. I'm going to have to take the valve cover off to get a good look at this. Do you think I'm looking at what we are discussing?
Steve
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
Originally Posted by AZC4Guy
So the wiring just runs straight thru the firewall to the ecm?
Same on the 86?
Same on the 86?
Drifting
Joined: May 2005
Posts: 1,302
Likes: 1
From: Tomahawk WI
Originally Posted by RRT vette
Yep, These guys have described fairly well and it's been a few years since I work on it. I believe there are two 7 mm screws that hold that connector on (86E). One on each side. Once the distrubitor is out it is fairly easy to access.
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Originally Posted by LD85
The ECM harness indeed runs thru the firewall, there is a round or a rectangular grommet that has a bracket around it that bolts to the firewall. This harness contains the fuel injectors and essentially most all of the engine management connectors.
Remove the bracket and pull the harness through, but this ECM harness is wire wrapped together with the two lengths of wiring that go thru the firewall behind the battery. They are individual harness's but they are all wrapped together.
Remove the bracket and pull the harness through, but this ECM harness is wire wrapped together with the two lengths of wiring that go thru the firewall behind the battery. They are individual harness's but they are all wrapped together.
And what was said above about the headlight harness running to the driverside of the firwall is also, to my knowledge, true. Close to the fusible links.
Race Director
Joined: Feb 1999
Posts: 12,772
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From: Indianapolis IN
Originally Posted by AZC4Guy
LD
Looks like mine is behind the passenger side valve cover and rectangular. I'm going to have to take the valve cover off to get a good look at this. Do you think I'm looking at what we are discussing?
Steve
Looks like mine is behind the passenger side valve cover and rectangular. I'm going to have to take the valve cover off to get a good look at this. Do you think I'm looking at what we are discussing?
Steve
Thread Starter
Drifting
Joined: Jan 2003
Posts: 1,894
Likes: 3
From: Reading PA.
CFI EFI Youre right there is a small bolt 1/4 inch right below the top harness at the firewall bulkhead. I removed it and the complete harness came out. Now after I remove the convoluted tube covering will I myself be able to seperate the engine wiring from the lighting harness or should I let this up to a pro? I'm switching over to a TPI and thought about letting Howell engineering change it over. Some of the harness does go into the firewall to the left of the AC condensor box. Can this be unhooked also. YOU GUY'S ARE GREAT HELP THANKS Pipe
Now after I remove the convoluted tube covering will I myself be able to seperate the engine wiring from the lighting harness or should I let this up to a pro? I'm switching over to a TPI and thought about letting Howell engineering change it over. Some of the harness does go into the firewall to the left of the AC condensor box. Can this be unhooked also. YOU GUY'S ARE GREAT HELP THANKS Pipe
Race Director
Joined: Feb 1999
Posts: 12,772
Likes: 17
From: Indianapolis IN
Originally Posted by pipe
CFI EFI Youre right there is a small bolt 1/4 inch right below the top harness at the firewall bulkhead. I removed it and the complete harness came out. Now after I remove the convoluted tube covering will I myself be able to seperate the engine wiring from the lighting harness or should I let this up to a pro? I'm switching over to a TPI and thought about letting Howell engineering change it over. Some of the harness does go into the firewall to the left of the AC condensor box. Can this be unhooked also. YOU GUY'S ARE GREAT HELP THANKS Pipe
Now after I remove the convoluted tube covering will I myself be able to seperate the engine wiring from the lighting harness or should I let this up to a pro? I'm switching over to a TPI and thought about letting Howell engineering change it over. Some of the harness does go into the firewall to the left of the AC condensor box. Can this be unhooked also. YOU GUY'S ARE GREAT HELP THANKS PipeJim can walk you thru what is needed for the swap.
I sent my 85 hanress to Jim for a full diagostic and he replaced faulty wiring and conectors, tested and re-wrapped the harness for $150.
I cant help you with an 84 harness,,,, I did the 1985/870 to a 1986-1989/165 ecm upgrade.
