Okay guys so here's my situation,

Background info
I picked up a piece of **** 74 coupe that had a 350 of some sort in it. I got it cheap and had every intention of turning it into a drag car so I didn't mind that everything was all hacked up. I drove the 350 until it finally blew up and then I began the BBC swap. Mechanically the car is complete and ready to go. When I did the swap I noticed how horribly brittle and hacked up the engine harness and forward lamp harness were so I bought new BB harnesses. I've hooked the majority of the new harness up but some things are not on my car and therefore a lot is disconnected. I'm missing the flip up lights, cowl hood, ac/heater stuff, oil pressure gauge sender, temp sender, and anti-theft system just to name the ones off the top of my head.

Current problems
Literally the entire car is dead after the starter. Battery is good and puts out the full 12v to the starter so the battery is solid. The starter can be jumped and sounds good so that rules the starter out. The purple wire is on the S lug, battery and red wires on the larger lug, and yellow terminal on the other small lug. I started testing down the line and both fuseable links are good and are allowing the full voltage to pass through them. On the driver side of the car there are 3 red wires (all hot) that I cannot figure out where to go. I believe they go on that stud under the drivers fender (junction box?), but even after trying that the car still won't crank. Lastly, I have an orange fuseable link that was cut or broken somewhere and goes to a black-white wire but I don't think it's related even though it's hot. My research on here and in the wiring diagrams shows it to lead to the ammeter. I know the fuse box is tight because I get continuity from under the dash out into the engine bay. Anyone have any ideas? My friends and I are all stumped.

Oh and it's not the seatbelt interlock because literally the whole car is dead. I can't even get headlights or interior lights.

Misc info
1974 Corvette coupe
4 speed
Original sb car swapped to a bb
Brand new engine harness (with seatbelt lock)
Brand new forward lamp harness
Not a single wire inside the car was touched

 

You might want to double check the two links down by the starter.

Is this the loose wire you mentioned? Point "B".

 

Both links by the starter are good as I am getting 12v after them.

That looks like the orange wire I am referring to. I will attach a picture below.

I have also attached a picture of the red wires I am unsure about and a picture of where I believe they go.

 

First pic:
Can't say for sure but that could be to or from the power window circuit breaker.
There is another orange with an inline fuse that goes to the heater relay, do you have that one already?



Second pic,
your horn relay is elsewhere, in 74 GM used that junction box.

 

All my research tells me that orange wire is either ammeter related or horn related, neither of which are needed to get the motor to crank, so I'm not worried about it at all right now. Once the motor can crank I'll start hunting down all the other gremlins in there.

Do you know anything about those 3 red wires? They're all hot so I'm leaning towards them being hooked up wrong somehow

 

Two of the three red wires should be for the horn relay (originally red with black stripe) and the third either goes to the top of the voltage regulator or the wire for the alternator. The one wire with the fusible link goes to the horn relay for sure.

 

My search shows the horn relay being located behind the dash on 74s and those wires certainly don't reach into the car. Perhaps I am overlooking or misunderstanding something here?

My alternator is already hooked up according to the diagram. The third red wire comes about 8" before the ones that go to the alternator.

Sorry if my terminology on anything is off, this is my first attempt at anything electrical.

Edit: zip shows the 74-78 horn relay as having flat terminals where as my 3 red wires are all eyelets. Is something on my car wrong or are we talking about 2 different sets of red wires? http://www.zip-corvette.com/catalog/...yGallery_10368

 

FWIW, I started testing for power at the bulkhead and the red wire from the forward lamp harness has power (top left on this picture) and the black wire from the engine harness also has power (black wire next to the light green one)

 

Condo,
I am not an expert by no means and only trying to help. I know that the location you show in the first pictures is where the horn relay is on my 68 BB and the wires look to be the same type and location. I wonder if the wire harness is not correct for what you are trying to do. Also looking at the last picture the connection between the harness and fuse box does not look good at all and could very well be your problem. Wish I could help more.

 

I doubt anyone here is any worse than I am with electrical stuff but I'm trying to learn so any help is welcomed and I appreciate you trying to help. I believe my 73 BB is set up the same as your 68 but unfortunately my 74 is different. I'm beginning to think my fuse box and interior harness are from another year because I cannot find anything related to the seatbelt interlock inside the car. Unfortunately it came with some weird seats and no seatbelts and is hacked to crap so who knows what it originally was. All I know is it worked before I changed the engine harness and now the engine harness works but not the fuse box. My mind is blown lol

 

Earlier years use the HORN RELAY as a junction box.
74 has the HORN RELAY near the fuse box and the JUNCTION box is a convenient place to attach several wires without splicing them. All those wires are battery positive voltage.



About the starter override system, is the new harness for a stick or automatic?

 

^ very good explanation, thank you for that. After the car runs that will also help me diagnose the horn so that's great.

The new harness is for a manual car and does have the interlock (which I will bypass by splicing light green to purple). The interlock is not the issue at hand because I don't get ANY power, not even lights.

 

Battery positive goes to the battery terminal on the solenoid.
From the solenoid a wire goes to the junction box.
Separate the wires at the junction box.
Another wire at the junction box goes to the alternator and ammeter.
Does the third wire bring power to the ignition switch?


https://docs.google.com/viewer?a=v&p...TRkNTFkY2E0NmM

 

That's the diagram I've been using but unfortunately I don't see the junction box on there so up until now I've mainly been looking over the forum at some other people's problems and going down the list 1 by 1

 

Here is the wiring diagram for my 68 if it helps any.

 

Thanks for your help but I've got the 74 diagram and even that can't help at this point. Something somewhere is just wrong or broken

 

Well, the heavy red at the firewall connector is the main feed for power into the cabin. If you have power on it then the interior should have power. Make sure it is still 12V when it is connected. Then, see if the interior side of the plug has 12V. This wire powers part of the fuse panel and also any of the heavy red wiring under the dash should be 12V.

Are the connectors clean in the firewall plug?

As for the wiring. Look at the diagram and follow the wires from the alternator on the B and 2 terminals down and to the left where there is a dot. That is one of the junction points with 5 wires connected, 1 is an orange fusible link feeding a black/white striped ammeter wire. Now, go to the left and you'll see another dot. That is another junction point with 3 wires connected, 1 being another orange fusible link with a black ammeter wire. Follow the wires and you should find these junctions.

I'm not positive which junction point is in your picture but I believe it is the first one with 5 wires connected, so you are missing 2 of them. The black/white wire you pictured broken off hooks up to the first junction point. The black wire you mentioned has power at the firewall plug goes to the second junction point.

 

Thanks for the detailed reply. I will have to check the actual voltage tomorrow but that big red wire is hot going into the box. The connectors look okay but cleaning them never hurts so I will do that as well.

The junction box pictured is the one near the alarm system. I believe that is the first one you're referring to but I do not see a second one in my car anywhere so I cannot be sure. The fuseable link for the ammeter is cut and, for now, is not connected. That makes a total of 4 wires (3 red, 1 for the ammeter) which means I have some searching to do to find another wire that connects there. There is 1 pink wire and 1 orange wire with eyelets that can reach but I believe those are for the alarm. Aside from those 2 I don't think I have any loose wires left on that side of the car.

Thank you very much for your help, it's definitely helping me clear things up.