Hey Fellow Vette Owners & Lovers,

I have a 1968 Corvette Coupe all original with 427 engine a 4spd Muncie.
I'm having trouble getting the brake lights to work right. I replaced the rear harness, several of the rear bulb brackets, Brake Switch and Headlight switch. In trouble shooting, I by-passed the fuse box and was able to get the brake lights to work, but now the taillight fuse blows when I turn on the headlights and the interior lights stay on.

Has anyone had this problem before and can you offer any fixes or suggestions?

The schematics in my Service Manual and Haynes Repair Manual are hard to read and complicating. Does anyone have a simple and clear wiring diagram or something that identifies each wire and color what it it's for and where it goes?

Very, Very Grateful, Thanks Scorpio-65

 

I did a quick google search and found a schematic for my '75 and it had the wire colors listed as well

 

This really should help you understand how the lamps work.. and help you solve the problem. I hope.

Most people don't realize the stop lamps go through the turn signal switch and/or how it works. The lamps are fed power on two wires.. One is the (both lamp) power and one wire is the turn only power. So in a nut shell... When you hit your brake lamps the power form the switch goes to the turn signal switch (not the rear). If you have the turn signal switch in the neutral position then power goes out to both lamps (green and yellow below). But if you have a turn signal on.. the power from the white wire is cut and switched to purple power wire (which has the flasher) for the side you are turning on.

So with this in mind.. you should start some diagnosis...

1) Always verify you have power coming out of the brake lamp switch or white wire.
2) Verify power on the pink wire at the flasher.
3) Place a jumper in line for the brake lamp switch (testing takes time) and disconnect your distributor power wire (save those points).
4) Once you have the power jumped at the switch then go to the turn signal switch and see if you have power on the white wire and the pink one.
5) If you have power at there and without the turn signals on you should have power coming out on yellow and dark green wires on the switch. If not then take a hard look at the connection for the t/s switch..
6) Test the flash.. turn the lever to one side or the other and test to see if power is pulsing on either Yellow or Green wires depending on side.

If all this works.. then I would go to the back of the car and start working forward by testing the grounds at the tail lamps and pinging the wires. The rear harness connector can sometimes be the culprit too.

You should never bypass a fuse for any reason…. This can and in most cases lead to a fire or damage to something else in the car.

I would check the turn signal switch as well.. go to this link and it will show you how. http://willcoxcorvette.com/repairand...lp.php?hID=266


Here are some recent threads about tail lamps and how they work and were fixed.
http://forums.corvetteforum.com/c3-t...t-working.html
http://forums.corvetteforum.com/c3-t...ke-lights.html

You can see the power to the lamps comes to the switch on one of the two wires.. Pink (flasher) and White (brake lamp switch). Once inside the switch it just makes a loop and comes out on the yellow and dark green...(unless you use the turn signal).. then is switches power.

Hope this makes sense.. and if you test good on the lamp switch and the turn signal switch you then move on to the rear connector on the car. Check your voltage there.. and then pull the sockets out and test there.

You could have a grounding issue too so if you have power at the tail lamps start looking for ground issue... All the rear lamp grounds are connected to the same circuit.. and there is a main ground at the rear of the car on the left hand side... If you have power to the lamps (with a test lamp to ground) then use the lamp ground to verify the ground is working...

Willcox

 

Too many 68 Lamp questions keep popping up so I made this today..

 

You guys never cease to amaze me! This in one reason I give Willcox as much business as I can.

 

You are definitely a God Send.

Thank You oh so much. Perfect, way more then I could have hoped for. I know this information is going to fix my problem. I only wish I was smart enough to come here, before I went head first into the problem. Would have probably saved me a lot of money (Harness, Brake switch, Headlight switch and a lot of time and frustration). I'm starting to think that all I probably need is a turn signal switch ( one of the only things I hadn't replaced). Oh well "Live and learn". On the bright side, the parts I replaced were very tired and would have needed to be replaced eventually.

So,So Grateful Scorpio-65

 

Glad to be of help Scorpio and thanks for the kind words Raphiki!

Hopefully this thread will pop up when others with a 68 are looking.



Willcox

 

Willcox, (While reading through the links to the other threads you provided me, I realized that your not Willcox, but rather an Expert representing Willcox. but I'm not sure if your (Lou, Earnie or I think Dan) So I identified you here as Willcox, sorry.)

When I went to start diagnosing and test my turn signal per your instructions and during a close examination I found the wires were real frail and the whole switch smells burnt, so I'd like to replace the whole thing (might as well have everything new). Problem is I want to give you my business as gratitude for your exceptional help, But you don't have any in stock. Part Number: 05698520-2121. And your system doesn't seem to allow me to backorder it. Any idea when you will have any and how I can give you my order?

Sorry to ask for more after all you have done, but I need to figure out why my fuse keeps blowing when I pull the headlight switch and why the interior lights stay on. When I crawled under the dash to fix the taillights, I found several loose wires and tried to find where they went using the schematic out of my Service manual, but again it is way hard to read. I think I may have messed-up. I thought I might have to replace the fuse/main Harness, but with luck you might have an easy to read schematic like the one you made and sent me on the taillights.

I am so Appreciative and as another member mentioned, thankful we have you as an asset to our forum.

 

Scorpio- I've corrected the link on the switch.. and lowered the price a tad... The switch, if out of stock is in stock at another supplier, I just checked. So you should be good to go.


What are the wire colors you are finding loose? Can you snap a clear picture of them and post it?

Most of the wires under the dash are from the main harness connection. But you'll find wires back there for the wiper over-ride, the wiper solenoid on the tach, the lamps, gauges and so on.. most can be identified. The 68 factory schematics are a bit of a mess for the 68 cars. I drew one a few years ago for the wiper system that took six or seven revisions before we got it 100 percent correct.

My advice to you is to start with on issue and then move forward. If the turn signal switch is toast this could be back feeding voltage to other parts of the car. Look hard at the other wires and make sure a short didn't cook the switch and make sure the switch didn't cook something else.

Ernie

 

Ernie,

I just ordered the Switch, should have it in 4, to 10, Working days. Thank you for the brake in price. Forgot to check, but does it come with the cam (Actuator) or do I need to order that separately?

I will definitely take your advise and take care of the taillight issue first and move forward, as you stated, chances are, replacing the switch will resolve some if not all my other problems (I hope).

Regarding the loose wires: I'll get the best picture I can for you tomorrow. But right off the top, I remember a white that I determined from the manual and what I can best figure, came off one of the instrument panel lights and it looks like it was attached to the side not the center of the light socket. The color didn't make sense, but the manual indicated it was a ground, so I connected it to the group of grounds in the harness. This one keeps coming to mind, since I wasn't a 100% sure and hesitant on grounding it. There is also a very thin yellow 18 or even smaller gauge close to the center console, that probably has to do with the radio or one of the center console gauges, but I couldn't figure it out. there's one or 2, more but I can't recall them. I'll work on these while I wait for the switch to come in.

Thanks Again, for all the help. I Really Do Appreciate it.
Mark

 

My pleasure Mark.. We'll get it fixed.. just be patient.

 

Ernie,

Sorry for the delay in responding with the requested pictures. I had a tragedy (lost my Sister). took a while, but realized that getting busy helps keep the loss off my mind.

I got a call from another Wilcox Representative ( I think Bobby). He informed me that he couldn't get the switch for me and had to cancel my order (I really wanted to give you my business). No problem, I still have a lot of restoring to do. I had no luck finding another at a reasonable price, so I relented and order an 67/68 Ac Delco Ecklers had on hand, but it requires an connection adapter and has an additional connection for what looks like a bulb, that my old switch doesn't have.

Attached are pictures of the loose wires behind the dash.

#1: Orange wire attached to back of switch.
#2: Yellow wire to connector attached to side of center console/Radio.
#3: Brown wire bundled with a white, yellow and purple they go behind the center console/radio.
#13: I can't figure out where this 2 prong connection goes.
#6: White behind bulb. Manual Says it's a ground, Connect green is from the car alarm.

I hope the attached pictures are clear enough for you. I exposed (Took all wrapping off) all the wiring behind the dash to try and find any more burnt or loose wires. I took pictures of all of it, but I couldn't add them here, since I reached the max allowed attachment, but can send them to you if you would like to see them.

I'm not going to install the new switch until I can get the pictures to you and then get your response. Since things aren't working right (Interior light staying on, and old turn signal switch smells burnt with frail wires etc.), I'm afraid the new one might get damaged.

As always. I really do appreciate all your help.
Mark