Hot Rods Where there's smoke...

Second the motion, please change the ammeter to a much safer voltmeter.

 

Glad things didn't get outtahand. A disconnect right under the dash might be a good idea and work as a theft preventative as well.

 

And I thought I was the only one to have weird crap like this happen...

A couple of things to think about. One, automotive ignition switches are only rated for 30 amps max, with some being less. They have poor arc-suppression as they're not intended to switch large currents. Make sure your continuous connected load is well under that number for good switch life. Generally speaking, once the arc suppression has failed the switch is toast. I'm not saying this is the problem here, but it could be. With that said....

I'd re-think that breaker choice. Automotive circuit breakers, while sharing some design aspects with household/commercial breakers, are considerably less sophisticated. Those contain several circuits, the most important being a current-sensing one that detects large overcurrents and quickly opens the breaker. Automotive breakers generally lack this, instead depending on only overload current (NOT short circuit current) to trip. How high the overload is will affect trip time, but these are slower to react. In effect, think of them as a giant turn signal flasher, although they're not designed to be cycled like a flasher. Excessive cycling will damage them.

If protecting a #10 wire, that current rating is 5 times the wire rating. I've seen smaller ones hold 30% over their rated current for as much as five minutes before tripping. Put 200 amps into a #10 for even a few minutes and damage is likely to result. If catastrophic short-circuit protection is what you're after, fuses work much better. Where it gets sticky is how many intermittent loads you have on that particular wire. I'll assume that this has very few of those, probably only the brake lights and turn signals if present. No electric fans, air bag compressor, power seat/windows, so calculating the continuous load should be easy. Add those up including the largest intermittent load and size your overcurrent protection accordingly.

This is why the OEMs rarely if ever fused these types of circuit wires. While the smaller wire could withstand the short-duration current spikes from the intermittent loads, the inability of breakers or fuses to recognize this meant that the overcurrent rating ended up being far in excess of the wire rating to avoid nuisance tripping, or basically no protection.

 

I’m just glad you caught it quickly. That could’ve escalated really fast. Keep us posted, as I know you’ll get it all sorted out.

 

HUZZAH! I found the REAL problem. First though, good call on the ammeter, I've bypassed it, due to the discolored post, thinking maybe that was really the issue, although it didn't explain the seemingly shorted switch. I bought a 100A breaker, the battery feed now energizes that instead of the ammeter, and everything is pulled from the "load" side of that. The ammeter isn't really needed (especially if it's bad) as the alternator has an indicator light that I can put in the gauge panel instead of the turn signal indicator (which I don't need either because the turn signal switch has it's own light).

I put it all back together, with a new switch, hooked up the battery and fired it up. No problem.

I put the gauge panel back in, hooked up the battery, turned the key and INSTANTLY got a puff of white smoke, and the breaker tripped.

Retracing my steps, I pulled the gauge pod, and again, the switch was hot. This time I noticed a tiny spot on the edge of the dash opening for the gauge pod that looked like it had arced to something. That "something" turned out to be the ignition terminal on the switch.

Because the original switch had a stem about an inch long that went through a long tube cast into the back of the gauge pod, I had moved the ignition switch the opening meant for a cigarette lighter next to the location for the original switch and put a lighter in that opening, close to the edge of the gauge pod. (I don't know what I did to get italics, but it works here for effect...) That put the switch VERY close to the edge of the dash opening, so close that occasionally the lug for the ignition wire could touch the metal dash, which is grounded to the steel firewall, body bracing, and the frame. That lead to a dead short with the ignition on, which melted the 10 gauge feeder to the starter, and made the ignition switch so hot I could barely touch it, and thus I blamed the switch.

I think the ammeter post is an innocent victim here, but I'm bypassing it anyway, just to be on the safe side. The wire to the coil from the switch had some heat damage right at the terminal to the switch, I replaced that wire as well to the coil just because I still had about 6 feet of that color linen wrapped wire left over.

I cut the opening in the dash a little at that bottom corner with a zip cut, put it back together, and no smoke, no smell, no problem. Every action has an equal and opposite re-action...

In other good news, I got my "Rodder's Journal" today, and feel like Pat Gahnal was looking out for me. ;-) I have a fire extinguisher I bought for the car but hadn't mounted yet because the interior is not finished. It's going in right now.

 

Yikes. I’m glad it wasn’t any worse that it was, and that the problem is sorted out. Yet another reminder to watch out for the “little” problems.

 

You can buy these 90 degree terminals, fit where straight ones don't and they're insulated

 

That would have been way cheaper than $49.00, with shipping, for the new switch...

 

Here is the good news, your up and running, learned a few things, and are now a wiser man! Hopefully!

 

Yeah, it was a learning experience. The main thing I learned was that it would have better to have shaved the inside of the gauge panel housing where the ignition switch was supposed to be, instead of thinking, "I'll just put that switch in the lighter opening because it's easier", and not nearly burn the car up. I shoulda checked that, but like John Belushi said, "But, NOOOOOOOOO..."

 

Glad it didn't cause to much damage. The battery disconnect switch is a great thing to have. I put one in the trunk of my roadster, mainly to kill the power for theft prevention. I came out one day and the horn was blaring, I have a button under the dash and after washing the car it filled with water and was grounding. Now every time I park I just turn off the switch. Just don't act all cool in front of everybody and try to start it without turning the switch on.

 

Brian, any time something happens anymore, the 1st thing I say is "what did I do?" I'm old and don't see well. You've built enough cars that you know what can happen. I'm glad it's not any worse than it was.

 

I wouldn't have been surprised to find a bad new switch. Bought one for my 84 F150 several years ago, as soon as you raise the column back up to bolt it in it would arc. Bad switch out of the box.

Being car guys, we like to put things where we like them over the factory location, been there, done that. Funny how similar spots like the switch and lighter look totally interchangeable from the outside, but will be just a bit different on the back side. I think we sometimes get carried away with our vision and overlook the small things in a rush to get things done, I know I have. Glad you got it figured out!

 

Totally beat me to it, they’re called flag terminals. If you’re going to run the straight terminal still and want to run the switch in the stock position, get some self fusing tape and wrap it around all the terminals as a group.

 

Forty-ish years ago a local guy built an OT VW kit car called a Kelmark GT. He had just finished and took downtown to the local hardware to show off to his buddies. When they went outside, it was in flames. Fire Dept only a block away, but it was too far gone by the time they got there. Cause was wiring defect per fire investigator. Worst part? The owner builder was a local electrician. It can happen to anybody.

 

I like those 50 amp maxi fuses. The one in my car came with the harness. I know some guys that omit them, makes no sense to me.

 

I bought one of those as well, and passed on it after I decided the breaker could be hidden up under the dash on the inside of the firewall. I may rethink and could put it "in-line" right at the lug on the starter. It'd be out of sight but accessible.

 

I'm totally okay with mine being visible and having good access to it. I can see wanting it out of sight to some.

 

Glad the car is OK Brian.

Suggest you replace the NAPA switch with a genuine Lucas unit. They are only three-position though - OFF, DIM and FLICKER

Cheers,
Harv

 

@flynbrian48 those breakers also make for good theft deterrents when open.

 

I thought about that as well. There's a little yellow "Test" button that trips it.

 

Brian,

Thanx for the thread. I've read it through. With your experience and others' comments I've learned some things that I'll refer to in the future.

 

Yep, just don't advertise where it is. I wire all of my cars with breakers after a fire nearly took out the 442 years ago.