Another wiring post - CorvetteForum - Chevrolet Corvette Forum Discussion

Notices
C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette

Another wiring post

Reply

 
 
 
Old 07-13-2018, 03:19 PM
  #1  
Jim__H
CF Senior Member
Thread Starter
 
Jim__H's Avatar
 
Member Since: Oct 2011
Location: San Jose CA
Posts: 199
Thanked 8 Times in 4 Posts
Default Another wiring post

Hi guys,
I'm now replacing the dash, console, and all of the wiring that I had to disconnect when I took it all apart a couple of years ago. Car is an early '77, build date Sept 1976, and this is the wiring diagram/schematic that I am using:

https://sites.google.com/a/c3vrmail....iring-diagrams

In the diagram it shows several terminal blocks some with numbered connections, my question is where are these located? It looks like they (or it) is sandwiched between the fuse box and firewall. If true, how does one access it? Putting the wiring back together that I took apart is not a problem but I also need to chase down a number of gremlins that were occurring in the short time that I drove the car before taking it down for a restomod. Like all four turn signals and the two indicators coming on when I turn the key, an intermittent problem that did not always happen. Probably a short somewhere but without access to those terminal connections it makes tracing the wiring paths.difficult. Unless I am missing something obvious which is always possible. Please enlighten me...

Jim

Last edited by Jim__H; 07-13-2018 at 03:21 PM.
Jim__H is offline  
Reply With Quote
Old 07-13-2018, 05:03 PM
  #2  
bmotojoe
CF Senior Member
 
bmotojoe's Avatar
 
Member Since: Oct 2007
Location: Seattle Area Washington
Posts: 702
Thanked 55 Times in 51 Posts
Default

Do yourself a favor and download Mr. Willcox 1977 drawing. It's a good drawing for an early build 77. If you're talking about the numbers inside the cells of the connectors, or bulkhead they are the actual circuit number. Right click lower drawing, save image as.....

http://repairs.willcoxcorvette.com/1...cer-schematic/

Last edited by bmotojoe; 07-13-2018 at 05:06 PM.
bmotojoe is offline  
Reply With Quote
Old 07-13-2018, 07:10 PM
  #3  
Jim__H
CF Senior Member
Thread Starter
 
Jim__H's Avatar
 
Member Since: Oct 2011
Location: San Jose CA
Posts: 199
Thanked 8 Times in 4 Posts
Default

Originally Posted by bmotojoe View Post
Do yourself a favor and download Mr. Willcox 1977 drawing. It's a good drawing for an early build 77. If you're talking about the numbers inside the cells of the connectors, or bulkhead they are the actual circuit number. Right click lower drawing, save image as.....

http://repairs.willcoxcorvette.com/1...cer-schematic/
I have that one too, problem is I can't print it out in any size larger than 8 1/2 x 11 to take out into the garage with me. I suppose I should take the file over to Office Max and have them print it out.

I just fixed the parking light/turn signal problem and a couple of other loose ends so for now I'm good...
Jim__H is offline  
Reply With Quote
Old 07-13-2018, 10:22 PM
  #4  
Shark Racer
CF Senior Member
Support Corvetteforum!
 
Shark Racer's Avatar
 
Member Since: Jan 2000
Location: San Jose CA
Posts: 11,937
Thanked 94 Times in 88 Posts
Default

FWIW, lectric limited sells some good blown-up wiring charts, 26x20.
Shark Racer is offline  
Reply With Quote
Old 07-13-2018, 11:20 PM
  #5  
Willcox Corvette
Premium Supporting Vendor
 
Willcox Corvette's Avatar
 
Member Since: Aug 2006
Location: Jeffersonville Indiana 812-288-7103
Posts: 62,358
Thanked 1,000 Times in 854 Posts
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Default

Originally Posted by Jim__H View Post
I have that one too, problem is I can't print it out in any size larger than 8 1/2 x 11 to take out into the garage with me. I suppose I should take the file over to Office Max and have them print it out.

I just fixed the parking light/turn signal problem and a couple of other loose ends so for now I'm good...
Don''t print it out.... open your paint program and paste it in there... then save it to your desktop. Once you do this you can open it in paint and trace out circuits... For instance say you have have a headlamp issue, you can trace out all the wires and then re-save it on your desktop under another name so you can go back and review it later if needed. We used these in our shop almost every day. Once you isolate the circuit then you can chop out what you don't need, bring the schematic together and then print out a simplified circuit... Hope this makes sense....

Willcox
Willcox Corvette is offline  
Reply With Quote
Old 07-14-2018, 07:47 AM
  #6  
Rotonda
CF Senior Member
 
Rotonda's Avatar
 
Member Since: Sep 2006
Location: Rotonda FL
Posts: 979
Thanked 55 Times in 51 Posts
Default

Originally Posted by Jim__H View Post
Hi guys,
I'm now replacing the dash, console, and all of the wiring that I had to disconnect when I took it all apart a couple of years ago. Car is an early '77, build date Sept 1976, and this is the wiring diagram/schematic that I am using:

https://sites.google.com/a/c3vrmail....iring-diagrams

In the diagram it shows several terminal blocks some with numbered connections, my question is where are these located? It looks like they (or it) is sandwiched between the fuse box and firewall. If true, how does one access it? Putting the wiring back together that I took apart is not a problem but I also need to chase down a number of gremlins that were occurring in the short time that I drove the car before taking it down for a restomod. Like all four turn signals and the two indicators coming on when I turn the key, an intermittent problem that did not always happen. Probably a short somewhere but without access to those terminal connections it makes tracing the wiring paths.difficult. Unless I am missing something obvious which is always possible. Please enlighten me...

Jim
Suggest that you look at DocRebuild.com. He has 11x17 laminated color charts that have photos of each connector, their placement, what (and where) they connect to, and the color and gauge of each wire. They make life MUCH easier! I also have an early 77 and the dash harness part# is 8977101 and the ignition/balance of car is 8977103.

FYI, there is nothing behind the fuse box except a hole in the firewall leading to the bundle-of-snakes wiring coming out into the engine compartment.
Rotonda is offline  
Reply With Quote
Old 07-14-2018, 03:08 PM
  #7  
Jim__H
CF Senior Member
Thread Starter
 
Jim__H's Avatar
 
Member Since: Oct 2011
Location: San Jose CA
Posts: 199
Thanked 8 Times in 4 Posts
Default

Originally Posted by Rotonda View Post
Suggest that you look at DocRebuild.com. He has 11x17 laminated color charts that have photos of each connector, their placement, what (and where) they connect to, and the color and gauge of each wire. They make life MUCH easier! I also have an early 77 and the dash harness part# is 8977101 and the ignition/balance of car is 8977103.

FYI, there is nothing behind the fuse box except a hole in the firewall leading to the bundle-of-snakes wiring coming out into the engine compartment.
Thanks Rotonda, I did see your reference to that in another thread. I might buy a set if I get in trouble again. BTW, you and I have talked before about your writeup on installing a Vintage Air unit in your '77. I refer to it often although I am going with the "stock" VA parts and installation. I am going to try to fab a center vent transition piece out of PVC or ABS tubing and sheet rather than make a mold and glassing it as you did. I'll let you all know how that goes.

So all the connections are on the back of the fuse box? Ok, that helps tracing since now I don't think I need to find some hidden terminal bus.

One new question for you all, does anyone know what the resistance of the rear defroster grid should be? When I throw the defroster switch the 20A Accessory fuse immediately blows. Measuring the resistance of the overall circuit I get less than 1 ohm, like ~ 0.3ohm which if accurate would certainly too much current for a 20 amp fuse. With the soldered connections at the window I am not sure what can be done, but I am wondering where a short might be and if I can find it maybe I can get it to work.
Jim__H is offline  
Reply With Quote
Old 07-14-2018, 05:02 PM
  #8  
SwampeastMike
CF Senior Member
 
SwampeastMike's Avatar
 
Member Since: May 2015
Location: Cape Girardeau Missouri
Posts: 1,386
Thanked 188 Times in 177 Posts
Default

While those "all-in-one" wiring diagrams are certainly useful I find the individual circuit schematics (and descriptions of operation) from the shop manual invaluable when tracking down electrical gremlins.
SwampeastMike is offline  
Reply With Quote
Old 07-15-2018, 08:15 AM
  #9  
Rotonda
CF Senior Member
 
Rotonda's Avatar
 
Member Since: Sep 2006
Location: Rotonda FL
Posts: 979
Thanked 55 Times in 51 Posts
Default

Originally Posted by Jim__H View Post
One new question for you all, does anyone know what the resistance of the rear defroster grid should be? When I throw the defroster switch the 20A Accessory fuse immediately blows. Measuring the resistance of the overall circuit I get less than 1 ohm, like ~ 0.3ohm which if accurate would certainly too much current for a 20 amp fuse. With the soldered connections at the window I am not sure what can be done, but I am wondering where a short might be and if I can find it maybe I can get it to work.
1) My reference states that the grid resistance should be 5 ohms
2) it is possible to repair the soldered connections where the wires join the grid. I don't recall where I got the necessary materials & instructions, but I will try to find the source.
3) The wires are attached to the grid at either side are 2 to 3 feet long and terminate above/behind the rear fenders, under the carpet. The passenger's side is the ground and driver's side the power. Suggest that you disconnect the ground side, put in another fuse, and try turning it on. If the fuse blows, you have a problem at either the switch or the area where the wires are attached to the glass.

SUGGESTION:
The switch is a one year only part for the 77 and is pretty much irreplaceable. I didn't care for the amount of load it was carrying so I installed a relay in the cavity near the rear window. The relay is controlled by the original wire, and I installed a separate 12 gauge wire (with in-line 20 amp fuse) directly to the battery and terminated it with a Packard 56 terminal that plugs directly into the window power wire. It works fine and the strain on the switch internals is now MUCH lower.

Last edited by Rotonda; 07-15-2018 at 08:18 AM.
Rotonda is offline  
Reply With Quote
Old 07-16-2018, 12:53 AM
  #10  
Jim__H
CF Senior Member
Thread Starter
 
Jim__H's Avatar
 
Member Since: Oct 2011
Location: San Jose CA
Posts: 199
Thanked 8 Times in 4 Posts
Default

Originally Posted by Rotonda View Post
1) My reference states that the grid resistance should be 5 ohms
2) it is possible to repair the soldered connections where the wires join the grid. I don't recall where I got the necessary materials & instructions, but I will try to find the source.
3) The wires are attached to the grid at either side are 2 to 3 feet long and terminate above/behind the rear fenders, under the carpet. The passenger's side is the ground and driver's side the power. Suggest that you disconnect the ground side, put in another fuse, and try turning it on. If the fuse blows, you have a problem at either the switch or the area where the wires are attached to the glass.

SUGGESTION:
The switch is a one year only part for the 77 and is pretty much irreplaceable. I didn't care for the amount of load it was carrying so I installed a relay in the cavity near the rear window. The relay is controlled by the original wire, and I installed a separate 12 gauge wire (with in-line 20 amp fuse) directly to the battery and terminated it with a Packard 56 terminal that plugs directly into the window power wire. It works fine and the strain on the switch internals is now MUCH lower.

I decided to punt on this one. Figuring that since I live in California, the car will be garaged all the time and I have interior RainX and plenty of small towels I can probably go without a rear window defroster. But that is some pretty impressive electrical re-engineering, Rotonda.
Jim__H is offline  
Reply With Quote
 
 
 


Thread Tools
Search this Thread
Sponsored Ads
Vendor Directory

Contact Us Archive Advertising Cookie Policy Privacy Statement Terms of Service

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: