sonny_burnett

I replaced the tach in my 71, when I got it back together and tried to start the car smoke, a lot of smoke, came from the driver side fender. I looked at a wiring diagram online and another thread on here and it's smoke coming from wires going into the horn relay. My car is stranded at a friends house now, so I'm not sure which wires, but going from the diagram I think the red wire on the far left in the schematic is the only wire that runs under the dash, at least the only connector I unplugged looks similar to what is shown there, it is located on the upper left corner of the driver side lower dash panel. I reconnected this, and I think it can only go in one way, so I don't know what I did to cause this, or how to fix it. Also, does anyone know where the other wires from the horn relay go, is this connector also under the dash somewhere?

Edit: After looking at the schematic more, it looks like the lower connector shown is the one I unplugged and plugged in again, I remember it was marked for headlights, so I'm not sure where the other connector is now.

sonny_burnett

it looks like the black wire that goes back to the headlight switch is fried and was arcing and smoking when the key was turned to start.

sonny_burnett

All I can think of is the headlight switch is bad, something is shorted inside of it causing the wire to burn out when I turn the key to start. It looks like power is coming into the headlight switch though the black wire that is burned out and the orange wire on the horn relay. Any thoughts?

Solid LT1

There is a fuseable link section from the horn relay terminal to the ignition switch wiring. I think you lost it......the same thing happened on my 72 LT-1 with 96K miles on it, it took a while to track down the problem to an abraded wiring loom behind the speedo/tach area of the dash. The wiring loom had abraded on the steering column cast iron bracket.

lionelhutz

It appears that's the main fusible link that feeds power into the passenger compartment. You say it only burns with the key in the start position so look for a short on the purple wire in the circuit that goes ignition switch -> neutral safety switch -> firewall plug -> starter solenoid.

Peterbuilt

Are you sure that black wire doesn't connect to your ammeter gauge?

sonny_burnett

Not really, didn't know it was a horn relay until this morning. The schematic is confusing to me, the wire that is damaged is solid black and looks like it is on the same terminal as the orange (looks red in the car) fusible link. But there is a 3rd black with white stripe wire on the terminal that isn't shown in the schematic. There is a black/blue white stripe wire nearby but it doesn't come into the relay on the schematic.

ETA: The black/blu white stripe wire is in series with the fusible link on the schematic, is this correct? Did someone bypass the link on my car?

lionelhutz

OK, the black wire that is smoking - is it a fusible link that connects to another wire color?

I was thinking it's the fusible link that powers the red wire which is the power for the passenger compartment. You could confirm this.

A picture a little further out or a list of wire colors and which ones have fusible links could help identify it.

sonny_burnett

sonny_burnett

Also, before I did anything to the car, it would not start if the column was tilted all the way up, lights would come on, and if it was running it would keep running, but couldn't start it. Moving the column down one notch would allow you to start it.

derekderek

you obviously have a wire grounding out in the column when tilting, so the insulation is rubbed off.

lionelhutz

Still can't make out where that black wire goes or if it's a fusible link connected to another wire.

But, I still expect there is a short on the purple starting wire.

Sometimes, you think you can get away with patching the original wire but I've found that even when the wiring seems OK that installing new harnesses still makes a big difference. You get rid of things acting flaky once all the circuits get a solid voltage supply again.

mysixtynine

temper my response with the fact that my car is a 69 ... not sure how close 69 is to 71....

If it only happens when you turn the key on to ACC or Run / Start then I dont think its your headlight switch.

Does it happen when the key is in ACC? ACC does not turn on things like the Ignition wire over to the coil but most other things work that would also work in Run (like radio, heater, wipers etc).

You have to keep in mind that there are alot of things powered all the time when the key is off. So if its not happening when the key is off then that eliminates those systems.

The black wire on the horn relay is tied (crimped) to the same connector as my amp gauge wire orange . Keep in mind they are crimped AT the connector which is the same really as have their own connector.

The black wire is a fuseible link that then turns into the Heavy red that goes into the bulkhead connector into the fuse panel.

The orange wire is a fusible link that turns into a black/wht wire that goes to my amp gauge. (see last sentence below as to why you dont have an orange wire here and instead have that blue crimp on connector directly to the Black / wht wire)

The heavy red goes several places and is live all the time whether the key is on or NOT!!!

1. It "Y's" off over to the headlight switch (no fuse) this works without the key ON HOT all the time this is why the headlights work with the key off

2. The other branch of the Y goes over to the fuse panel and feeds three fuses (Curtesy fuse / BATT terminal, Hazards and Tail lights ) this works without the key ON Hot all the time and why your courtesy lights , BATT , hazards, tail lights , clock , cigarette lighter all work with the key off )

3. There is then another Y off over to the ignition switch and to the Wiper door interlock connector (no fuse). The ignition swtich feeds the rest of the fuse panel for ACC or Run and has the radio, heater, wiper motor , gauges and the ignition wire for the coil and the starter relay etc)

You have to determine now is it only in the Run position or in ACC as well. That would help eliminate the coil / ignition portion of the ignition switch run.

Yanking the dash and pulling the tach allows you to mess with alot of wires and possibly crush some when you put the dash back in where the harness goes up over the steering column support bracket.

If you unscrew and pull the dash away does it still happen? Maybe your crushing something in the wire harness run over the column support?

Keep in mind the ignition switch is on the top of column under the dash so you could have pinched somehting there as well.

Make sure you didnt pinch any wires between the column and support bracket that hold the column up to the column support. You must have had to drop the column down to get the dash out... could pinch wires in between the column and support when put the 3 bolts back in.

***I just looked at your picture again and noticed someone removed the orange fuseible link that goes to the black /wht wire (you have a blue crimp connector on their now with no fuseible link) which should be one side of your amp gauge... not really a good idea as there is no protection in your dash if that amp wire shorts to ground.. that wire will burn up into the car without a fuseible link on it. I dont think its related to your current issue but you need to address this for the future****

sonny_burnett

I pulled the center guage cluster out to make sure nothing was shorting across the ammeter, still smoked. Also I noted that it smokes when turned to run, not start. No issues when the key is turned backward, but the key won't stay unless held. I lowered the column (removed the bolts underneath and loosened the nuts at the firewall) and was able to start it without any problems, it looks like something in the column or connected to the column is the short. I think I will have to remove the driver side lower dash to get to the connectors on the column, they are too far back to reach with the dash in place.

lionelhutz

Smoking with the key in the On position could mean there is an issue on the pink wire that comes off the ignition switch. The short would have to be on the main wire before it goes to the fuse block and gets fused because that would have blown the fuse instead of burning the fusible link.

GM typically uses red as power to the switch, pink as the switched ignition power, brown as the switched accessory power and purple as the start wire on their ignition switches.

Peterbuilt

Maybe not!
With the seat out and the column unbolted you might be able to get to the switch.
Here's a photo of it.

sonny_burnett

[QUOTE=Peterbuilt;1590399890]Maybe not!
With the seat out and the column unbolted you might be able to get to the switch.
Here's a photo of it.


Too late, took the lower dash pad out last night. I didn't see any obvious pinching or burned wires other than the dark green on the light switch connector. Also noted that my wiper solenoid isn't connected to the vacuum lines. I haven't disconnected the two plugs on the column, I'm wondering if I should pull the column out, if it's the pink wire, and its in the column I'm guessing the column had to be disassembled to get to it.

Peterbuilt

The base of the switch (the metal part) is held to the column just by two screws.
The wires are all outside the column.
Only the turn signal wires go up the column. You can see the harmonica connection on the far right.

Remove the BLACK plug first.
Going back together WHITE first.

Your in good hands with Lionelhutz so follow his instructions.

Solid LT1

[QUOTE=sonny_burnett;1590402946]Take a real close look at the dash wiring harness and confirm it is intact with no chafing anywhere. My 72 LT-1 had electrical gremlins that finally revealed themselves when I put an oversized piece of fuseable link on the stater and horn connections. The other possibility could be you turn signal wiring or ignition switch wiring. You might want yo get a Dr Rebuild wiring schematic as they are the best wiring references available for a Corvette. Good luck in your troubleshooting this job isn't fun.

sonny_burnett

Orange wire a few inches back from the connector on the column is pinched, the small blue wire next to it that goes to terminal j in the harmonica is also pinched, but not as bad.<br/><br/>

Better picture