Dash wiring.

[Ken Harants]

Need some info. After installing my rebuilt instrument panel, I turned on the igniton and smoke came from behind the dash. After removing the dash I found the cigarette lighter wire had burned up. Know all of the electrical is not working. No lights, will not start. Any suggestions. The only wire damaged is the cigarette wire.

[Ken Harants]

Re: Dash wiring.

Sorry, I left out that this is a 1966 Corvette.

[Ken Harants]

Re: Dash wiring.

Sorry, I left out that this is a 1966 Corvette.

[Robert S.]

Re: Dash wiring.

I don't have a wiring diagram but I'd look to see if a fusable link burnt up when the lighter shorted out.

[Alan Drake]

Re: Dash wiring.

Ken,
First find out what caused the short! Remove lighter and measure for a short.
You will need a wiring diagram for the 66 before you go trouble shooting. Try one of the wiring people in the DriveLine or NCRS has diagrams in one book for all C2s. If you plan to purchase some material from NCRS the AIM has diagram also, however check and make sure it is the correct year, my 64 was wrong.

Just because you only saw one melted wire - does not mean there isn't another one inside the tape.

Sorry about your problem, hope mine's alright when I power it back up. (I just may check it first now)
Alan

[William C.]

Re: Dash wiring.

OK, one thing to remember is that there are no fusible links in a '66 and there are also unfused circuits, one of which is the Cigar lighter. The Cigar lighter is fed fronm a splice in the IP which is fed from a 12ga wire. Any damage is likely to be in the section from the cigar lighter to the splice. As mentioned, first find the ground point and fix it. Then you will likely have to untape the harness from the lighter back to the splice looking for damage to other wires in the harness that could have been damaged by contact with the 14ga red from the lighter when that wire overheated. Repair as necessary, retape and check.

[John H.]

Re: Dash wiring.

Check to make sure you haven't mis-connected the long BROWN wire with a single black connector on it and the long BLACK wire with a single black connector on it; the BLACK wire is the cluster ground (plugs on a spade just above the tachometer), and the BROWN wire is "hot" with the key on, and plugs on the radio capacitor attached adjacent to the ignition switch.

If the lighter feed wire fried, there's a dead short in the lighter, between the center connection and the lighter housing. Be aware that if your lighter is a replacement Casco restoration part, they have added a U-shaped bi-metallic element at the feed connection; this was done due to folks plugging everything they own into the lighter socket for power, overheating the housing, resulting in instrument panel fires in some modern cars. The bi-metallic element is designed to dead-short the lighter internally if it gets too hot, which will blow the fuse in '67 and later Corvettes. The bad news is that '66 and earlier Corvettes don't have a fuse on that circuit, and a dead short will fry the harness all the way back to the battery. Photo below of the U-shaped bi-metallic element in place - just remove the nut, pitch the element, and re-install the nut to eliminate this potential source of fried harnesses.

[Ken Edmunds]

Re: Dash wiring.

Ken, I have seen a couple of fried brand new harnesses. One time was my own fault. Both times were caused by the oil pressure line contacting the ballast resistor under the hood. When the harness is installed, there is a lot of shifting of wires and oil pressure line. Check your oil line for signs of contact. Also check that the ground wire at the starter is not connected to the center post on the starter solenoid.
Ken Edmunds

[Jack H.]

On Cig Lighters...

There are two potential causes for failure here that should be investigated...

(1) Today's 'replacement' lighter sockets have a 'safety' feature that can be DEATH to older cars. They have a bi-metal overload protector that senses excess current draw from the lighter socket and INTENTIONALLY short circuits the system (B+ to ground) to force the branch circuit fuse to blow.

Now, what's wrong with this design 'feature' is it PRESUMES there's an upstream fuse and that isn't the case on the older classic cars. To determine if your cig lighter socket has this newer design feature, remove the socket and look at the back.

There should be a threaded electrode stud centered in the circular opening of the rear. Factory orignal cars had a brass 'baby nipple' adaptor screwed onto the threaded stud while common replacement sockets discarded the adaptor and screwed an L-shaped slide terminal onto the stud. The modern replacement socket will have a rectangular strip of bi-metal around the electrode stud held in place by the stud's mounting nut. The strip runs horizontally to the stud with the ends of the bi-metal strip simply hanging in the breeze. That strip is the safety feature...

You simply unscrew the power stud's mounting nut and remove the bi-metal strip. Which takes us to issue number two.

(2) The socket's power stud is insulated from the socket's outer wall components which are grounded by contact to the instrument cluster. The electrical isolation is achieved by properly centering the power stud in the socket's oversize mounting holes at the base and keeping it in that position by a non-ferrous insulating washer and the pressure of the stud's mounting nut against the insulating washer.

If a cig socket has been disassembled (say to install an incorrect L-shaped, slide terminal because the factory original 'baby bottle' nipple was missing), it's possible the socket's hardware was mis-aligned and/or improperly stacked resulting in the power electrode to make a DEAD SHORT contact to the outer case metal components (electrical ground). In that case, kiss your upstream wiring bye bye the first time you apply power to the car!

[James G.]

Re: Dash wiring.

Not pushing products here, but Lectric Limited in Illnois at www.CorvetteHarness.com phone 708-563-04000 and M&H Electric in Southern California at www.wiringharness.com phone 562-926-9552 make excellent replacement harnesses.

Don't you think your 40 year old car deserves a new main wire harness? Especially the underhood area?

In the 70's and 80's when I fixed these cars the first time, we replaced the complete harness. The stupid fires that can cause a total loss, more than justify the nominal cost to replace the entire system.

Besides, once you learn to stand on your head replacing the unit there is a real feeling of accomplishment. And it is a good time to refresh that dash gague cluster while your at it.

[Jean C.]

On Cig Lighters...Safety issue

John & Jack, thanks for the very informative posts. On an item like a cig lighter that has a high power load through it and is not fuse protected, is it possible to install a fuse/fuse link in the wiring? If it is possible and if it were done, would this be deemed a owner installed safety item at Flight Judging?
Best regards,
Charlie

[John H.]

Re: On Cig Lighters...Safety issue

If I had a '66 or earlier, I'd install an in-line fuseholder and not worry about a possible one-point deduction for a cut wire.

[Dick W.]

Re: On Cig Lighters...Safety issue

Charlie, I am sure an enterprising individual like you could find a concealed location to mount a fuse holder. The newer inline fuse holders use the "blade" style fuse that would be even easier to conceal. Not that any of us would do anything that did not come from St. Louis.

[Randy S.]

Re: On Cig Lighters...Safety issue

John,

You wrote an article a few months back in Corvette Enthusiast about installing a fusible link at the starter on 1966 an earlier Corvettes due to the lack of overload protection.

Will this link protect the cigar lighter circuit?

Randy

[Eugene B.]

Re: On Cig Lighters...Safety issue

John,
If one is going to install an in-line fuse holder for the cigarette lighter, what amperage fuse would you recommend?

I have already installed a fuse in the main (red) wire at the starter per your suggestion. I have also added a fuse to protect the clock motor if the points stick. My car is a '65.

Thanks for all your information.

Best regards,
Gene