Late C3 Fuse Box Internals
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
Late C3 Fuse Box Internals
Anyone take apart or by chance have pics of the insides of a late C3 (probably 78-82 should be close). Issue I have is the lead that goes from the Starter to the Firewall then comes out and goes to the Post on the back of the alternator bit the dust. I pulled the engine harness off and checked continuity from the starter to the box and the box to the alternator and continuity is fine. But, however they are connected within the box is bad. I have no continuity or voltage going from the Starter to the Alternator so there is no charging and it's pizzin me off! 
Getting at the interior side of the fuse box sucks, even with the seat out. I really don't feel like pulling the dash all apart yet but will if I have to. But it I could just see what the internals of the box look like I might be able to either figure something out or run a bypass wire.
Thanks!
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Getting at the interior side of the fuse box sucks, even with the seat out. I really don't feel like pulling the dash all apart yet but will if I have to. But it I could just see what the internals of the box look like I might be able to either figure something out or run a bypass wire.
Thanks!
\
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
Hate to say this, but many late shark, and even going back to mid year vettes, have bad fuse blocks....they RUST/corrode, quite often heating the wiring up in the process, melting insulation, take a good hard look at the wires themselves....
the spring clips are steel, and were stamped/crimped to the bus bar connectors on the backside, the wires were crimped also....
well that springy steel rusts, and it's over.....
I would get a hotrod wiring fuse/power center, and replace it with later spade lug fuses....far easier, and superior wiring materials....
the spring clips are steel, and were stamped/crimped to the bus bar connectors on the backside, the wires were crimped also....
well that springy steel rusts, and it's over.....
I would get a hotrod wiring fuse/power center, and replace it with later spade lug fuses....far easier, and superior wiring materials....
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
It's my 81. But the dash harness was out of an 80.
I did check both the fusible links and the connector behind the engine and I have voltage there. The engine and forward headlight harness were new and I had problems with the blinkers and markers which I had to fix way back. Things were fine until recently. The dash harness unfortunately was used. Being I only needed some of it I figured I would save $700-800 on a new one and it was fine until recently.
Should have replaced it at this point:
Obviously pulling the entire dash out to replace the dash harness would suck but if I can't get around the issue I will.
Keep the suggestions coming. If anyone has a fuse box lying around they don't need, would love to see the inside of it.
I did check both the fusible links and the connector behind the engine and I have voltage there. The engine and forward headlight harness were new and I had problems with the blinkers and markers which I had to fix way back. Things were fine until recently. The dash harness unfortunately was used. Being I only needed some of it I figured I would save $700-800 on a new one and it was fine until recently.
Should have replaced it at this point:
Obviously pulling the entire dash out to replace the dash harness would suck but if I can't get around the issue I will.
Keep the suggestions coming. If anyone has a fuse box lying around they don't need, would love to see the inside of it.
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
Yes. the red lead at the connector has 12v constant and the exciter wire has 12v switched. I thought of just splitting this wire to the post on the back and am sitting here looking at how it maps on the wiring diagram and service manual. If I split it though I would imaging then it's not going to backfeed the charge into the car and to the battery but not sure yet. Needs a freakin' magnifying glass for these wiring diagrams. Tough to get old!
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Race Director
Joined: May 2006
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From: Dayton, Ohio
Yes. the red lead at the connector has 12v constant and the exciter wire has 12v switched. I thought of just splitting this wire to the post on the back and am sitting here looking at how it maps on the wiring diagram and service manual. If I split it though I would imaging then it's not going to backfeed the charge into the car and to the battery but not sure yet. Needs a freakin' magnifying glass for these wiring diagrams. Tough to get old!
edit-- the diagrams are incorrect because they show the wires going inside the bulkhead connector and conneting to one another but they dont.
2nd edit--some diagrams show the 2 wires going through the bulkhead and coming together inside and some show the leads coming together in the plastic tubing a few inches from the alternator.The 78 I am looking at comes together in the plastic tubing with only 1 wire going through the bulkhead.
Last edited by ...Roger...; Jul 12, 2009 at 06:16 PM.
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
Thanks DW for all the tips and pic.
The later C3 connector has the Hazard unit directly on the other side of the connection (The hazards work).
This is the culprit was up under the dash. Looks like I am going to have to pull the two screws that hold it and hope I have enough slack to get some access to it. If not, the dash is coming out. Bummer.
Thanks again.
The later C3 connector has the Hazard unit directly on the other side of the connection (The hazards work).
This is the culprit was up under the dash. Looks like I am going to have to pull the two screws that hold it and hope I have enough slack to get some access to it. If not, the dash is coming out. Bummer.
Thanks again.
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
One big PITA but found the problem tonight. The main lead that runs from the circuit box up to behind the dash that also feeds power to the Alternator was melted down inside the box. Almost took a few other wires with it but it looks salvageable but just a pain.
Question of course is why and why didn't the fusible link at the starter go first? Have to poor over the wiring diagram some more to see if I can find something that stands out. At least the mystery of the alternator is solved but I'm not exactly happy about it. My back hurts!!!
Question of course is why and why didn't the fusible link at the starter go first? Have to poor over the wiring diagram some more to see if I can find something that stands out. At least the mystery of the alternator is solved but I'm not exactly happy about it. My back hurts!!!
Thread Starter
Le Mans Master
Joined: Feb 2000
Posts: 7,032
Likes: 2
From: Newburgh NY
I've got it all sorted out. There is a line comes in from the alternator through one bulkhead, goes through the ignition, headlight, heater, etc. and then out the other bulkhead and down to the starter.
The 130 amp alternator melted this wire with too much load and resistance on it. I cut out and replaced the bad piece and then used a 10gauge wire with maxi fuse directly between the alternator and starter to soak up the extra amps (path of least resistance). This sends it right back to the battery but everything else works just fine and stays cool. I spoke with painless wiring and others here and found out this is standard procedure in a high amp alt situation.
So what could have been a disaster was an easy fix and I'm on the road. But thanks much for the offer@!@
Pics and parts numbers if anyone is having a similar problem or plan to upgrade to a high amp alt at:
http://forums.corvetteforum.com/c3-t...rs-wiring.html
Last edited by 78Vette-SA; Aug 1, 2009 at 03:06 PM.
Le Mans Master
Joined: Jun 2005
Posts: 5,447
Likes: 3
From: Syracuse NY
