saunderscx

Ok, found some similar threads but still haven't been able to solve my problem. Here's the deal.

The car cranked up just fine (as always). Decided to test head / tail lights before a cruise. While the car was running I pulled the headlight switch out to power the lights & the engine shut down immediately. Turning key won't spin the starter. Clock on dash not ticking off seconds. Radio dead. The only thing that works is the horn.

Battery is fine. I measure 12V at alternator red wire & also 12V at the starter solenoid. By virtue of that I believe my battery ground / power cables are OK. I also measure 12V at some sort of power block mounted to driver side fender. I measure 12V at another unknown small block mounted to firewall (2 screws on side with wires).

The fuses checked out for continuity (low R) so they don't appear to be blown. When I turn on the key and check fuses with a test light it seems there's no power to the cabin side of the fuse panel.

I'm thinking the problem may be related to the headlight switch as when I turned it on that's precisely when the engine died immediately. I've never had any electrical trouble before now. Solving this problem would appear to be easy (like a main power fuse) but I'm completely stuck in finding a solution.

DOES ANYONE KNOW IF THE POWER FEEDING THE FUSE PANEL FROM THE ENGINE SIDE ROUTES THROUGH THE LIGHT SWITCH ? If yes perhaps changing the light switch will solve the problem. Or are there any fuses in the engine bay side of the equation ? If yes I sure don't see any.

I really don't suspect the fuse panel itself is the problem. It's the original fuse box & while far from super clean the fact no fuses are blown seems to indicate there is another cause. Plus I've never had a power problem until today.


If a failed light switch can render the car totally dead that is a horrible design flaw, but I'm kind of hoping that's it as I'm out of ideas.

Ideas & suggestions are most welcome.

vbgod1

What year is this, so we can pull up a wiring diagram and run some traces? Top of my head, mayhaps you burned a fusible link at the starter wires. Must be a hella draw on the lights tho, if you did that.

69Vett

the switch shorted the system when you pulled the head light switch,
you most likely blew the fuseable link, location depends upon the year.
most likely near the starter harness.

0Willcox Corvette

I think the car is a 1972 and if I'm correct you'll have two fuse links at the horn relay and one red fuse link right by the firewall and one at the starter.

Check to see but I believe the red one by the firewall till take out everything from that wire back if it's blown. I'm looking for my schematic right now.

And if it is blown, head my warning... only replace it with fuse link. While one blown link may take out a huge section of the electrical power, it can in the long run save you from a huge issue which would be much worse if it didn't blow.

Willcox

saunderscx

Yes, it's a 1972

saunderscx

Thank you so much. At least now I have hope. Are the red markings in your figure the location of the fuse links (thanks so much if that's the case). I'll order some tomorrow and see if that will work.
Another question. When I do order them they are all the same PN or specific to location in the figures ? Hopefully they are all the same. As for why any of them blew out, that's a bit of a mystery. Never had any shorting or other problems in the past. I'll be sure to order extras too as if this happens to occur again I won't get hosed on another $150 tow.

My horn still works.

saunderscx

I'll replace the fuse links to start. Do you feel mostly confident I should replace the light switch too ? Assuming it's got a short in it.

0Willcox Corvette

Yes, the red lines are the links approximate position. You should be able to purchase some fuse link from your local parts store.

Kubs

I just went through something similar. I measured 12v but couldn't get power at fuse box. Just because a wire can carry 12v doesn't mean it's ok. Use a light bulb to test and see if you can get it to light up. I had to replace the fusable link at the starter.

vbgod1

It may not be the switch. The switch allows power to the circuit, the short could be further down the line.

A short version of what happens when you pull the switch, voltage goes thru the switch to the wires and through the bulbs. The bulbs act as resistors and use up the voltage to create light when the circuit is complete, and everything works. In the case of a short, which it sounds like you have, instead of going thru the resistors and using the voltage, it is going straight to ground, allowing full current flow, and burning the fused link (as it is supposed to). Somewhere, between the switch and the bulbs, I would be looking for a pinched or open wire sending power straight to ground, could be headlights, tail lights, side markers... Do any work around those areas lately?

saunderscx

On looking for Fusible Link product online I see there are varying gauges. One link I read said to use a fusible link which is 4 sizes smaller than the wire you're connecting to. Not entirely sure what to go with. Some websites offer specific AWG. Others say "universal". 14 AWG seems to be popular. Do you remember what AWG you used ?

http://www.wiringdepot.com/store/p/7...%20%26%20Cable

For the 2 links on the fender well block (ring connector one end / barrel crimp other) it looks like these are available pre-made

http://www.dormanproducts.com/itemde...7&SEName=85620

Maybe go with 14 GA on all ?

saunderscx

Only recent work was replace rotors/calipers. I'll definitely continue to look for a bare wire but so far not seeing any signs of that at all. My only guess at this point is the light switch itself. I hope I can easily find the fuse links. After screwing with it for 7 hours today & before seeing all these posts I ran out of energy. I'll start with soldering in a new fuse link nearest the starter & replace the light switch, check, then proceed with the other fuse links if needed. The real moment of truth once I can start the car again will be when I turn on the lights. If the fuse link(s) blow out again I'll loose my mind. haha (seriously). I'll look as closely as I can at the lighting wires before turning them on again.

Kubs

The factory fusable links look like they are just sized down wire. I didn't see anything different about them. Also note the length of the smaller wire is important too. Try to match the stock configuration. I made my own fusbale links. The factory power wire off the starter to the horn relay is 12ga wire, so I used 16 gauge for the fusable link. I soldered mine in and reused the rubber grommets that go around the solder joints. I also crimped on new ring terminals where needed, and I like to put a dab of solder on those as well, and then wrap them in heat shrink tubing.

saunderscx

Thank you Kubs. I'll order some 16 AWG fuseable link wire & do the 'starter' link first. I'll use red heat shrink so it's obvious where the fuse link is located. In parallel I'll do my best to trace all lighting wires looking for any signs of shorting or missing wire insulation. I'll pull the dash panel back enough check for any anything obvious at the light switch. As the headlights go up/down it could be the case the short happened up front. I'll continue to post updates as I dig though this pain in the butt problem. I'm desperately hoping I do find the short as I can't feel comfortable driving the car anywhere if it's got the potential to DIE in an instant. Not finding the short almost means re-wiring the whole vehicle and that would take me forever to do alone w/o having first hand experience. This is such a drag as the balance of the car is in great condition (mechanically) after replacing, fixing, or rebuilding just about everything you can think of.

croaker

I found some at Napa on the wire rack.

Kubs

Hang in there! It took me about a week of working 2-3 hour per night in the garage tracing my issue. There were times I wanted to just burn the garage down and collect the insurance money on the car, but not matter how frustrating it may get you WILL find the issue and it WILL work properly again.

vbgod1

Just an afterthought, you may not "see" where the wire is burned, as it usually does not burn the insulation. The insulation is kind of rubbery, and pulling in the burned area with a finger may feel loved me there is no wire in it.

saunderscx

Hi Croaker. Thanks for the tip. I already ordered two 3 foot lengths of 16 AWG and some red heat shrink online from a company called Wiring Depot. But will keep this in mind. Decided to go with red heat shrink so the fuseable link locations are clear (hopefully will never need that conconvenience in the future !!)

http://www.wiringdepot.com/store/p/7...%20%26%20Cable

saunderscx

Hi Kubs. Thanks man. I appreciate the encouragement. I'm really hoping it doesn't take more than a full day now that I have a game plan, but that may not be realistic. Today I ordered some fuseable link wire and red heat shrink (so the fuseable links are easy to locate in the future...if necessary...which I hope I never have to touch again !!). I will get started in about two days when it arrives. I'll start replacing the fuse links 1 by 1 (starter side first) until such time I have 'normal' power again on the cabin side (gauges, radio, dash lights and starter works). Based on the feedback from you & others it might be the case just the starter side fuse link is blown. After I have cabin side power again I'll dig into the tedious inspection of the lighting wires. On having 48 hours to think more about this issue this short has got to be really severe and has got to be in the headlight / front running lights wires. I mean the engine died INSTANTLY when I pulled the light switch on.

Also I was thinking about cause. Vbgod1 asked me "did you do any work recently that might have caused this". I paid a Corvette shop (just 2 weeks ago) to rebuild / install my steering box. This guy works ONLY on corvettes & does quality work so I didn't think it was related but on looking at the manual I see the headlight / parking light wires run right along the same side (driver side) very near steering box. I also hadn't turned on the headlights not even once since that install.... until 2 days ago when the melt down happened. That makes me think he may have knicked a wire wrangling in the steering box so I'll focus on that area in searching for the short. In retrospect it's just an awfully big coincidence for a car that's never even blown a glass fuse in over 20 years. Don't you think ?

If I struggle to no avail, I'll possibly look into the nuclear option of a replacement harness.

saunderscx

Hi Vbgod1 - great tip. That didn't occur to me. Considering the 'direct short' burned fuselinks / killed the engine instantly when I turned on the headlights I'm definitely leaning toward a wire in contact with the frame or other metal. On thinking further I'm kinda doubting the light switch is the problem (can't rule that out though). Also when you asked me about recent work I did have a corvette shop rebuild & install my steering box just 2 weeks ago. When the melt down happened that was the FIRST TIME I had turned on the head lights. Too much of a coincidence especially for a car that hasn't so much as blown a glass fuse in 2 decades. I'm thinking the shop mechanic may have accidentally knicked a wire wrangling the box in there. The headlamp / running light wires are routed right in that area on the driver side so it seems a strong possibility. I'll focus inspection on that area to start. Thanks so much for the guidance & help. I really appreciate it.