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Connection went up in smoke...


Onion

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I revved my car sitting still maybe 3-4 times to maybe 7000 RPM (hot cam, so not redline). On the 4th rev, I got some smoke coming out of the steering column. 

 

I popped the steering column cover off and found out that a connector had melted and burnt. I'm not sure what its called, and what the two bad cables are, let alone how to fix it... Maybe some of you more talented electrical guys on here can help me? I disconnected it and tried to start the car just to see if I had to push it back into the garage or not, and it did start. However, the headlights don't turn on, the dash lights don't turn on, and the blinkers don't work.

 

Here's what the connector and the damage look like. 

 

2J97R.jpg

 

2J98H.jpg

 

2J99l.jpg

 

Also, the car's having an inspection sometime this week, or early next week, and I need it to pass, so if this is a hard, long, and tedious fix, is there any bandaid fix I can do to make it pass and then fix it properly once I have the time?

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Well does that connetion run to the turnsignal/headlight combo switch? I bet it does

 

First off, what year is this Z? and secondly do you know if anything in the electrical has been changed from stock (upgraded alternator)?

 

Sorry, I forgot to include the info. Its a 1973 240Z. And yeah, I'm sure it leads to that switch. As far as the alternator, I've got no idea, but the previous owner didn't mention it. Are there any telltale signs or easy ways for me to differentiate an aftermarket one compared to the stock 40 amp one? For things in the electrical that have been changed from stock, the previous owner put in an electrical ignition and a Holley carb. I'm sure there are other things that have been modified because there are a couple dead ends in the wiring harness, the AC doesn't do anything when you turn the switch, and the wipers used to turn on randomly. 

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Looks like the Green/White and Green/Blue were the two affected.  It also looks as if those are the running ("park") lights - activated by the first turn of the light stalk.  Were they on during your engine revving? 

 

For now, cut them (the two wires) off each side of the connectors and crimp on a male bullet connector on one side and a female bullet connector on the other side and plug everything back together.  (or use male and female spades - just be sure the connector you use is covered so that once connected, no metal is exposed to short out the connection)  If you can, get some DeOxIt  (Deoxit) and spray all the metal pins and sockets on all the connectors before you put them back together.

 

Check to see that everything works and the wiring isn't heating up.  It may have been resistance in the connector itself, but you may need to check the wiring, connectors, grounds, bulbs, switch, and etc. on the running lamp system...

 

You can decide later if you want / need to replace that 9-pin connector and it's wiring.

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The revving to 7000 RPM shouldn't cause a short circuit.  The voltage regulator controls voltage.  You probably knocked one of the loose wires to ground when your leg was pumping up and down on the gas pedal.  And that circuit should probably have a fuse on it.  I would look to see why it didn't blow. 

 

 

I don't think that "redline" is determined by the cam profile. 

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Looks like the Green/White and Green/Blue were the two affected.  It also looks as if those are the running ("park") lights - activated by the first turn of the light stalk.  Were they on during your engine revving? 

 

For now, cut them (the two wires) off each side of the connectors and crimp on a male bullet connector on one side and a female bullet connector on the other side and plug everything back together.  (or use male and female spades - just be sure the connector you use is covered so that once connected, no metal is exposed to short out the connection)  If you can, get some DeOxIt  (Deoxit) and spray all the metal pins and sockets on all the connectors before you put them back together.

 

Check to see that everything works and the wiring isn't heating up.  It may have been resistance in the connector itself, but you may need to check the wiring, connectors, grounds, bulbs, switch, and etc. on the running lamp system...

 

You can decide later if you want / need to replace that 9-pin connector and it's wiring.

 

Nope, the lights were off, both times. Same for the blinkers. I was just sitting in the driveway in neutral and gave it some gas. 

 

I'll do the wiring work tomorrow and do what I did the last two times and feel around to see if the wires heat up at all. Hopefully it works. Thanks a lot for your reply. 

 

NewZed, I'm 100% sure I didn't knock anything when pumping the gas, there's nothing dangling under the steering column or dash or anything.

 

Edit: I'm bought DeOxit D100 as TomoHawk recommended and I'll try to get some gunk off the connector and see if it makes any difference. I'll go on from there and maybe just bypass that connector. 

Edited by Onion
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Check your combo switch and the fuse block. There might be indications of heat at the wires on the combo switch as well.

 

Typical problem with the 240z's. Fuse block and all the amps for the lights going through the combo switch. The parking light fuse is the one usually that melts the fuse block.

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I inspected the connector more closely today and it literally just fell apart in my hands. I'm thinking of just cutting the wires on either side and then using spade connectors to wire it back up and still be able to disconnect for whatever reason. Does anyone know what gauge the wiring is under there? What gauge should I use for the patch? Is 16 gauge fine? Thanks in advance.

 

2Kf4J.jpg

 

2Kf73.jpg

 

2Kf7l.jpg

Edited by Onion
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Check alternator output while you're working on things.  If you have bad regulation, the rev to 7000 RPM would cause higher voltage > higher current flow > more heat from resistive heating on your bad connections > melting and smoke.  That would be one logical cause and effect path.

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With the connector unplugged, I would also try checking for continuity between every wire on both sides of the plug to ground to see if you are shorted out somewhere like that. On the switch side, I would go thru some motion in the switch and column while checking to see if its a moving part causing it.

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You can sort of see it on the last picture, but there are two blue/white wires on the connector. The connector fell apart and the wires fell out of place, so I don't know which one goes to what. How could I tell which wire goes to what and what to plug it back into? I can't really trace the wires as they go through a sort of harness. Any advice on that?

 

Thanks Matt, I'll try that. 

Edited by Onion
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Awesome. :D Everything works now! Thanks everyone for the help. All that's left is figuring out those two spare connectors that plug in to another one of the same color (except all 4 are the same color), but that's easy. 

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