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Discussion Starter #1
I posted this on alfaowner.com, but will try here too.

On my 1979 Spider Veloce, I recently instituted the recommended fix to my hazard switch which had gone wonky and drained my battery (with the cover on the car, I did not notice that the flashers were on for a week). I inserted the tiny plastic shim, which fixed the switch and all seemed to be ok. I was pretty careful in documenting how the wires were attached to the switch when I removed it, so I am pretty sure I rewired correctly. I cannot guarantee that all of the lights were working after fixing the hazard switch, but I am pretty sure that I tested everything.

Now, a month later, I noticed that my marker and rear lights were out. I replaced fuse 5, and when I tested it, it immediately started smoking. So either I rewired the hazard switch incorrectly, or have an unrelated short somewhere.

The only work done since the hazard switch repair was replacing the muffler, which I don't think would cause the short, as the wires all run inside the car body.

It has however been raining a lot here on the Cape recently, what with all of the tropical storms, and I did notice some moisture in the trunk, so am letting it air out.

So I have 2 questions:

1) Can anyone provide me with the correct wiring for the hazard switch.

2) What is the best way to track down a short in the fuse 5 circuit? The only thing I can think of is to disconnect all of the lights on the circuit, and then put in a fuse and try them one at a time, because the fuse blows so fast, and I don't want to start a fire or fry the wires.

Thanks in advance.
 

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Discussion Starter #3
Thanks you DGHII. I have already requested one of papajam's awesome diagrams. My question still is how best to diagnose the short.
 

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The much cheaper glass fuses, or similar, as long as they are roughly the same length and amperage, from a local auto parts store have worked for me on a temporary basis while doing the one part of the circuit at a time tracking exercise. Get handful. The bad circuit will always be the last one you check.
 

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what exactly do you have on fuse 5 on your car?
 

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Discussion Starter #6
Lightweight- am worried about doing damage if I replace the fuse. It was smoking hot within 30 seconds.

Spiderserie4 - Fuse 5 seems to control the dash lights, the glove box light, the side marker lights and the taillights, but not the turn signals, brake light or headlights. Not sure if it controls the front parking lights (if there are any).
 

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First things first. With the #5 fuse removed take your meter and measure resistance between the fused side of the the fuse panel and ground. You should see some resistance value...certainly nothing close to just a few ohms. You might even consider repeating the test on another circuit (say fuse 6) as a comparison. The value will not be the same but it will give you and idea of a typical circuit resistance value.

If the circuits on fuse 5 appear to be short, you will have to identify all of the components and disconnect them one at a time. Just be patient and methodical and you will find your problem.
 

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Kudos to Don. I looked all over the Internet for a reasonable approach, and in some of my old physics textbooks, but never found as rational an approach to an all too routine problem for those of us who own cars made, as an old engineer friend said, by nations that do not understand electricity (and whose products do not improve in those functions with age). Thanks, and that one is going in my collection of ways to approach difficulties.

It only took me a month to figure out my latest electrical glitch, which I tried so many different ways to fix that I've forgotten what finally worked.

Good luck and good hunting Alishaleff!
 

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If you connect a 12 volt lamp across the fuse holder contacts instead of the fuse, the lamp will illuminate but current should be limited to the lamp current. When you remove the short the lamp should go out or at least dim if current is passing through other items like another lamp(s).
 

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have you taken out the fuse box right out (with all wires connected) and looked behind to see if there is a burnt contact/connection anywhere? (if so, you can then note the colour and trace it back to the culprit)

I did this on my S4 fusebox, and the amount of wires behind the darn thing feeding into it lookes like a bowl of spaghetti - but i found one browned connector which i replaced.
 

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Discussion Starter #12
Thanks, all, I really like the lamp idea. My idea had been to connect a model railroad battery instead of a car battery, so at least I wouldn't start a fire, but I think the lamp idea is better.

I will try Don's rational approach.

Also, I think I have eliminated the hazard switch as the problem, as the hazards work just fine with fuse 5 removed (as one would expect, given the wiring).

Guess I have my weekend's work cut out for me.
 

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Discussion Starter #13 (Edited)
Solved ( and now the radio works too!)

So I went out and bought a test lamp for $2.99 and spent the day diagnosing the problem. Since the problem occurred only after I had removed and replaced the console to fix the hazard switch, I removed the console again, and voila the lights on fuse 5 now worked, so clearly the short was under the console cover. I found 6 wires that were not connected, but none of those tested hot, so I taped them off and bundled them together. There was a 7th wire that had clearly become disconnected from a terminal block, and I reconnected that one. The 6 wires that I taped off were probably left over from when the '79 console cover was replaced with a '79-1/2 cover from a parts car. I replaced the console cover and all of the lights still worked.

So, heady with my electrical success on fuse 5, I decided to diagnose the radio. About 2 years ago, I removed fuse 4, as the battery kept dying if I stored the car for more than a week, and as a result I had no radio/cd player. The radio has a removable faceplate, and there is an amplifier under the rear deck. I had the deck cover off anyway, as water collects under there due to my leaky convertible roof, and a tiny hole in the plastic rear window. I suspected that the water had affected the amp, so I set about testing it. I put fuse 4 back in, and with the key out of the ignition, the power terminal on the amp was hot, but oddly, so was the ground. Now the radio should have power without the key, as there a is a little LED that blinks on the dash when the removable faceplate is off, but it made no sense that the ground wire should ever be hot. With fuse 4 in, the radio and power antenna worked, but there was no sound from the speakers. In reading the amp user manual online, it mentioned that the amp will shut off if it senses an electrical problem. I disconnected the ground wire, which was connected under the terminal block on the amp, where I couldn't see it without a dentist's mirror, and reconnected it above the terminal block. Now I have power to the speakers, and will try leaving fuse 4 in and hope that the battery doesn't drain. A car battery should be able to power a single, blinking LED for at least a month or 2, right?

Thanks to all who offered their help.
 

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There should be no power on a ground wire. Power on a ground wire means the ground wire was connected to a +12vdc source.

Your battery will be fine with one LED binking. If your battery goes dead, take it as a sign you are not driving your car enough!
 

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Power in a ground wire could also mean you have a bad ground at the chassis end of the wire. Power will exit the device and appear as a full voltage potential if there is an open ground connection.
 

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Now, that's what I'm talkin' about!

alishaleff :

Congratulations for the clearly stated summary of your problem, including a detailed summary of symptoms, efforts made to date, quick response to folks who made suggestions and finally, a healthy helping of "crow" after you discovered, in the immortal words of Pogo "We have met the enemy and he is us". Cant' begin to guess how many time I have deluded myself into thinking my last repair/modification effort could not possibly have anything to do with: rear bumper falling off, familiar looking tire/wheel rolling past me on the freeway, clanking in the rear due to untorqued bolts on the reaction triangle that finally loosened, etc. Always good to recheck all your premises (sp?).

I believe there is a saying in the medical community (among others) that goes something like this: "If you hear hoof beats, don't look up and expect to see a zebra"...ie: don't start dragging out all the hi-tech equipment before you carefully reconsider what you just did and where you were last.

Again, thanks for making time to write up a detailed summary of the solution.

All other slackers, please take note :D !!

Be safe.
 

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Discussion Starter #17
Thank you Steve for your kind words. I hope I never see a familiar looking wheel rolling past me on the freeway!

-Robert
 
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