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Hello all, long time, no see. Which is good since I typically only come here when something is bad... anyway I've got this problem, see?

 

Started a bit ago, a little trouble getting the car to start. Classic *click* when I'd turn the key. Checked wiring on my starter, since one has come off in the past leading to this problem... not this time. I rock the car a little in desperation (I'm on a dirt road, quite far from civilization at this point) and somehow it starts up. Whew, I think.

 

I get home. Try turning it on again? Click. all wires connected. OK, must be the battery. I get a jump from a neighbor, run it for a while and I turn on the lights to see how it's going. This kills it. Well. Not going to bug the neighbor again, wait for my girl to come home. Jump it, run over to the neighborhood Napa. Guy comes out to test the battery and alternator. He says battery is bad, alternator is good. I had to jump it to get this tested.

Jump again to drive over to AutoZone because I still have the battery under warranty until March (Bought it just shy of two years ago). Guy verifies battery is no good, I replace it, but not before brushing the cables free of any possible corrosion. Car won't start. I jump it to go home because I don't know what else to do, and I need to get to work asap anyway at this point, so now I'm borrowing my girl's car for work. Thanks babe!

But still not sure about this car. I have a multimeter that I am a little familiar with, use it to test the ground, and it's good. I jump it again and decide to just run it a bit to see if the battery was just dead from the store (it had almost no charge at this point). I run for a little bit and LO! There's smoke coming out of the dash vents on the driver's side! Electrical smell. Great. I'm about to pull the dash apart, which I've never done before and am not looking forward to because my best guess is a short somewhere in there. It's not a well-educated guess. Any ideas?

 

Car info:

'73 240z with l28 and upgraded windshield wiper motor ('94 Accord, I believe) and upgraded MSA fuse box, both of which were done over two years ago.

no radio, no A/C, no heat connected (core just sitting there) and none of that has been changed/touched in years.

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Check the harness plugs under the dash and in the engine bay (there's a single plug under the dash near the fire wall penetration, large gauge wire white with red trace). I had a very similar issue with mine but got to it before it smoked. It was melting due to poor contact, this created more resistance and then pulled more current until the plug melted completely with part of the wire insulation was damaged also. 

 

Amp meter in the positive means something is pulling current/power, like lights on high beam, thermo fans etc. Mine used to flick intermittently and stay in the positive without any lights or fans running.

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That's good advice from Gareth. J. The wiring and connectors to the ammeter is a known source of car fires on old 240z's.  The ammeter sees full system current all the way up to the gauge.  Old corroded wires and connectors build up resistance across the connections leading to heat build-up, melted insulation/connectors and finally fire.  I'd recommend ditching the ammeter for a voltmeter.  You don't have to pull the dash and there are instructions how to do it on this site.

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22 hours ago, skillinp said:

Oh, and I forgot to mention that I noticed the little amp meter was reading a little to the (+) side. I don't know what that means

 

 + means the alternator is supplying more power than the system is using.  That's normal, and good.   - means it isn't, that the battery is supplying the power.

 

Apparently, ammeters, or the big wires that supply them, go bad sometimes.  They just burn up.

 

http://www.viczcar.com/forum/topic/15680-mysterious-burnt-out-wires-under-dash/

 

image.png.1b5a946a3e2364f1f38151b511e7e6fa.png

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Might possibly also be the ignition switch wiring (which runs alongside the steering column) or the switch itself.  The harness is designed such that full amperage runs through the switch, and when connections get old and corroded, it starts to heat up and melt electrical connectors and plugs.  A good solution is the clean all your plugs and connections, and insert a relay into the system so that the ignition switch is not carrying the full electrical load.

 

If your battery is dying when the car's not running, there is a draw somewhere in the system (stereo, alarm, etc).  A quick start to tracking down the draw is to pull the fuses one at a time and see which circuit is draining the battery when the ignition's shut off.  If that doesn't do it, you'll have to dive deeper into the various electrical harnesses with a multimeter.  Electrical gremlins are a pain.

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Ok, thank you all so much for your time and ideas. It turns out that I'm just a big idiot. I couldn't find whatever was smoking, almost took the dash off in my search. It took me a long time to even get to this point because I've been busy with school and work and the daylight just isn't what it is during the summer months (yet).

ANYWAY. I get out the multimeter and do some more tests. I figure I'll try to make it smoke some more with the middle panel and vent panels out so I can see where it's coming from. This means I have to jump start it again, but I wanted to see how the voltage was doing before. OH, LOOK AT THAT, the battery is at 12.3 ish volts. THAT'S WEIRD. so I touch to the engine, yup, still 12.3, so the ground is good. Maybe I should actually test the positive connection. Hmm... would you look at that, it's only giving 3 volts. So I'm a big idiot. I take off the terminal and clean it (again! I swear to god, I brushed and cleaned very thoroughly when I changed the battery), notice there was some grease which came off. Don't know how it got on there.

Starts right up when I reattach battery to terminal. I swear. to. god. I can't believe I'm so dumb.

Drive it around the next day, it stopped again. Popped the hood, cleaned the terminals again, works again. WTF. I think it must be the anti-corrosion grease I bought which came with the felt pads when I got the battery. Never been an issue before, so idk why it seems like it's an insulator now. Fun story on the picture, before I cleaned the terminals off the second time, I found I could jump the car to itself using the battery which had a poor connection.

Anyway, sorry for wasting everyone's time, but thought you deserved an update.

 

TL;DR: OP is an idiot and didn't clean the grease off the positive terminal of the battery when installing. It was the battery's connection the whole time.

2018-03-08 10.55.42.jpg

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None of what you wrote explains the smoke.  Be careful.  You have more smoke waiting to come out.

 

I don't know what you're "brushing" your battery terminals with, or what kind of grease you're putting on, but there's a simple $2 tool made specifically for cleaning terminals using hard wire brushes, and no grease is necessary.  You can get the took, called a battery terminal cleaner, at any auto parts store, or hardware store, or Harbor Freight.  Clean them up, leave the grease off, and clamp them down tightly using a wrench.

 

Check under the dash for wire ends that are brown or burnt.  Wire connections get loose or corroded and generate heat.  Check the back of the ammeter.

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1 hour ago, NewZed said:

None of what you wrote explains the smoke.  Be careful.  You have more smoke waiting to come out.

 

I don't know what you're "brushing" your battery terminals with, or what kind of grease you're putting on, but there's a simple $2 tool made specifically for cleaning terminals using hard wire brushes, and no grease is necessary.  You can get the took, called a battery terminal cleaner, at any auto parts store, or hardware store, or Harbor Freight.  Clean them up, leave the grease off, and clamp them down tightly using a wrench.

 

Check under the dash for wire ends that are brown or burnt.  Wire connections get loose or corroded and generate heat.  Check the back of the ammeter.

Yeah, I'm not sure about the smoke, which worries me still. I couldn't find anything that looked melted or burned at all.

 

For the cleaning, I used a wire brush to get off the corrosion, and I used this stuff: https://www.autozone.com/greases-and-gear-oil/lubricant-grease/ags-battery-install-kit-with-grease-and-washers/554868_0_0

 

Also, the ammeter is reading at neutral again, like it used to. Since so much of my system is inactive, I really don't know what could have been smoking. I don't have a heater, no A/C for that year, I have a hole where the radio went, the lights all work and the wipers too. Only other thing are the gauges and the ignition switch, all of which seem to be fine. given the way the smoke came from, I would have thought gauges, since all the lights and the wipers are wired through the steering column, and nothing was smoking through there.

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