I've trouble shooting why I have no power to any of my accessories. I have power to the alternator, battery gage, and 2 terminals in the fire wall. I also have power to these wires but I cant seem to find where the connect.

 

My '68 has a thick red wire that attaches to the horn relay AND then goes to the firewall fuse block. It also has a thick red wire that comes from the starter solenoid.
Probe your thick red wires...at least one of them should be hot and goes into the firewall to supply power to the fuses and to the Ignition Switch. When the Switch is turned to the ON position all the fuses receive power (I think)

Upper connector.....



What year car do you own?
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Use a large straight pin attached to a voltage meter to pierce the wire. Also check the fusible link wires at the starter. You should have a year specific Chevrolet Service Manual that has a wiring schematic in the back, then you can test other wires ie. horn relay. Good Hunting!

 

On my 1968 C3 the fusible links protect the accessories and wiring inside the Corvette. I found 2 of them down by the starter and they went up and towards the Horn relay. There will be no power going down to the dashboard after they blow. Fusible links look like a small rubber tube on the wire. I measure continuity to verify the fusible links are still good, if they are open then they need to be replaced.

If you use the pins and poke tiny holes in the wire's insulation be sure to put silicone, heat shrink or something to plug the hole. Water gets into holes and can corrode the wire inside so never leave any holes in wire's insulation. Boat grade (Marine) heat shrink has the same shrinking characteristics but has an extra feature that is awesome. The marine heat shrink has a Heat Activated glue Inside the heat shrink and it seals out water and air.

The big issue is that many Corvette owners want to up-size their alternator and wonder about where to send the newfound output from the alternator. On my 1968 the power was made by the alternator and then thru the voltage regulator and to the horn relay where it eventually goes thru the ammeter. There is NO WAY I would wire up the charging system to feed the new 100+ amp output through the original wiring made for a 63 amp alternator. Instead I ran the new output from the Alternator Output to the Starter's "battery" Post. This gives the power a good path to the battery and keeps you from overloading the capabilities of the 40 amp ammeter.

In the original configuration those fusible links would go as the last line of defense for the Corvettes Electrical System. If the fusible links don't burn, then the possibility of damage in the electrical system gets very real.
If you find the fusible links burnt that would indicate that there had been a bad short in your electrical system at some point. I had a Electric fan Controller and one day I started the engine and "Pow", the little control box started smoking and that was what blew my fusible links. It was a BAD short and I was very glad that my fusible links gave up and burnt.

Fortunately replacing a fusible link is not that hard to do. You can get them at NAPA stores or on Amazon. The fusible links need to be soldered into the electrical system, no wire nuts. Once they are soldered in I shrink the heat shrink over the connection and seal it up forever. After my experience I went and ordered an extra set of the fusible links just to have spares on the shelf.

I hope that information is of use to the original thread starter. DocRebuild sells some really nice Color Wiring diagrams for the 1968 Corvette. He has one that shows the connectors and tells you what they go to. I have them all along with a very nice layout chart for the vacuum lines. I put a set of DocRebuild vacuum hoses on my Corvette more than 32 years ago and they still works and look great after all this time. I wipe them down with a silicone oil that keeps the vacuum hoses more soft and supple which helps them last longer. 20 years after the hoses were installed the Vacuum operated parts still "Jump" to action.

Quality parts for an awesome Corvette, the 1968 427 Corvette!