The problem is that the car runs fine until you push the brake pedal and then it shuts off. The previous owner run a wire from the alternator to the solinoid on the starter and it fixed it for awhile. Then he took it to a repair shop and they replaced the negative battery terminal and that worked for a week or two. They said the the copper in the terminal wire had turned to powder. I notice that when just the switch is on engine off and you step on the brake the voltage gauge drops alot. I also noticed that the alternator belt was really loose, i can turn it by hand its so loose. Im gonna start with replaceing that but was wondering where i need to start after that if thats not the problem?

 

I hate electrical problems...here's a bump for you.

 

Thanks! Ive been reading the problems you are having.

 

Sounds like there is a power wire (12vdc) near the brake pedal mechanism which is rubbing as you depress the pedal. Insulation has probably worn thru and is grounding out the 12v. system....at least enough to kill the ignition. Look under the dash, anywhere there are moving parts connected to the brake pedal, and you'll probably see your problem. P.S. I would disconnect the battery before making this check....a dead-short can be nasty.

 

I agree with 7T1vette, you need to address this asap... a hot wire like that loose and uninsulated could ruin your car in a burst of flames... pull the dash and go through the harness....

Sully

 

I looked under the dash tonite to see what was going on. I found what looks to be a resistor spliced in to the wires on the brake switch. It has a metal bracket in the middle,On the left hand side it says MGIS .47 200 and on the right hand side 2P47-2 Mfd vdc The symbol for ground 10%. Does anybody know what this would have been put there for?

 

I can't imagine why there would be a resistor there. It would seem to me that you are dealing with a short to ground in the brake light circuit. Time to pull out the multimeter.

 

That's a factory installed capacitor that eliminates the 'pop' sound you'd get on the AM radio when the switch makes/breaks contact. All radio equipped cars had them.

 

Do a thread search for "electrical diagrams".. Papawana is the original poster and he is providing electrical diagrams that cover your year as well. I received one from him for my 73 and it is dead on. It will help to let you know what should and should not be there. It's always scary when previous owners monkey around with wiring when they are not schooled on it. I looked at my schematic and it does not show a resistor. You'll want to take a look at your years schematic. Send Papawana a P.M. and he will get one to you I am sure.

 

Did you exercise the brake pedal and look for any wiring rubbing against anything that moved? [I understand your curiosity about the resistor (anti-pop capacitor), but did your focus on that cause you to limit your investigation?]

 

I had a bad ground in the brake light wires that connect to the rear lights and when the brake switch turned on the circuit would backfeed and cause the instruments to flutter and energize the ignition system.
I don't know if this is relevant to your problem but it might be worth checking the grounds in the brake light circuit and make sure the lights are all equally bright.

 

No i didnt let that stop me from searching for any other problems. Theres no wires in the area for the pedal to rub agianst and cause a problem. I just recieved a wiring diagram from papawana this evening. So ill check it out tomarrow sometime. So does it sound like my problem is in the brake wiring harness??? Any help whats so ever is greatly appreciated because this problem is driving me NUTS!

 

[QUOTE=Fordtruckman;1564717359 So does it sound like my problem is in the brake wiring harness??? Any help whats so ever is greatly appreciated because this problem is driving me NUTS! [/QUOTE]

Easy to check. Disconnect the wires from the switch and step on the pedal to see if the motor still dies.

 

Got it running today and figured out that the problem is in the brake lite wires. Was wondering what was the best way to pin point the problem spot. I cleaned all the grounds to no avail. Also while i had it running i pulled the headlight switch and it has the same effect, it kills the engine. I contribute this to a problem in the wireing going to the tail lites. Cuz u only have to pull it out to the parking lites for it to kill the engine. Help I wanna get this thing going. Also how does the harness run to the back of the car?

 

My bad wire was the actual connection of the wire to the eye terminal not the terminal to the ground post. The wire had been overheated from a poor connection and the wire itself was brittle and discolored to the point that it didn't even look like copper anymore.
Connect a jumper wire to a good ground source and run the jumper to the grounds on each tail light until you find the one thats not grounding properly.

 

If I remember correctly, the tail light harness runs under the driver's side door sill plate, then under the rear cargo area carpet, then finally out the back through a grommet that leads to the tail lights. You'll find where it connects to the dash harness under the driver's side kick panel or in that vicinity. I'd disconnect the tail light harness from the dash harness and see if your problem persists. If you find it's in the tail light harness, use a continuity light and check the pins in the connector one by one. If you have a wiring diagram you should be able to trace out what wires go where. Hopefully, you'll find a short or bad ground.

Because of the fiberglass bodies, these cars have a lot of ground connections. If the ground connections go bad, strange things can happen.

Good Luck! Trouble shooting electrical problems can be exasperating. Just take a logical approach and you'll find the problem.

 

I was also informed that that this car has had the brake lite switch changed. He said that when he picked up the switch he was informed that they made two for that car. He picked up the cheaper switch. Does the 68 year take a specific switch, could this be my problem?

 

The '68 does use a one year only switch. I actually found mine to be bad after I was nearly finished with my car. It was one of the few items in my electrical system that I did not replace with new when restoring it. The switch was causing a short and blowing a fuse when I'd step on the brake. Oddly, it tested good before I re-installed it. I took it apart and found that a sliding contact had worn through to the point that it was grounding on the case of the switch. I was able to repair the switch by fabricating a new switch contact.

Other guys have replaced their '68 specific switch with the much more commonly used push button style switch that was used in '69 and later models. These are available at just about any auto parts store as they were used by many more models than Corvette. It requires making a custom bracket due to the different style switch but this is probably no less work than what I did. You can probably do a search and find more details about how to make the bracket.

A couple years ago at a swap meet, I found a vendor that was selling NOS electrical parts. He had a tub full of switches similar to the '68 Corvette style brake light switch. The only difference was the configuration of the arm that contacts the brake pedal. He said the switches were for older (I assume '68 vintage) Chevy trucks. I bought a couple just for curiosity's sake to see if I could modify it to work with my Corvette. I think he only charged me about $5 a switch. If you find a NOS '68 Corvette specific brake switch for sale on ebay or from a vendor, they tend to be expensive.

 

how do i do a ohms test on this harness??

 

Were you able to disconnect the tail light harness at its connection to the dash harness?