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Which circuits don't have a fuse? White smoke from under dash- panic ensues

Got in my car and before I closed the door I had to throw some stuff in the back. Before I even started it, I started to smell and see white smoke from under the passenger glove box and saw the wires under the ignition switch start to smoke too.
Popped the bonnet to disconnect battery (with the tool kit tools) and saw the wire to my bonnet light in the hood smoking too.
Disconnected battery, pulled all nonessential fuses, got a cup of coffee nearby and reconnected the battery. No more smoke, and proceeded to drive home 3 miles.

Where would you start?? Why wouldn't a fuse blow?
Damn I hate electrical

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1986 930, 1969 Mach1, 2003 540 Sport, 2016 R1200RS
Old 06-26-2015, 08:10 AM
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The glove box light is on fuse 1, along with the clock, trunk light, and dome lights. The glove box may be where the problem lies, especially since you said it started under the glove box, but the circuit was powered because the dome lights were on. Start your search there and see if the shared connection with the black wire is solid and not shorted to ground. The circuit for those lights is always hot so disconnecting the battery was the right move, but now you can remove fuse 1. You'll need to trace the wires from the glove box back toward the ignition to inspect damage not only to the wire itself, but to any wires that had contact with it. You need to be sure the wire insulation is sound as it is a hot circuit at all times. The circuit is not connected to the ignition switch but the wires come in contact with wires from all over. Take a close look with a flash light.
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Last edited by ossiblue; 06-26-2015 at 08:46 AM..
Old 06-26-2015, 08:43 AM
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As above, not ALL circuits are fused. A good way to check for a short to earth, would be using your multi meter as follows.

Turn your multimeter to contunity (audible if you have one). If not ohms. Now to test your meter connect both leads together, something will happen, either a buzz or the needle will move.

Okay now insert one lead on the battery negative (or any ground/earth). With the other lead, put it on each side of the fuse terminal in the fuse box, check all fuse terminals (both sides). if any beep or the meter swings then that is the circuit.

but as you say you did not blow a fuse, so chances are you wont find anything. Start by taking out the burnt wires and then probing the end of the wires you cut to see if any are going to earth. It might be that the bit that was earthed went up in smoke.
Old 06-26-2015, 08:58 AM
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The wiring to the light in the frunk shorting to earth and burning up is a classic one. The connectors come apart over time or through wire abrasion and then eventually it will touch something (probably the body) and the smoke gets let out. Very frustrating.

On my '82 SC the dash lighting circuit was not fused. You can easily add an inline fuse at the light switch. Search the forum there is a lot of discussion about it. Also add JWest or similar headlight relays for safety on the column high beam switch. On the Carerra's you need to add fuses for the footwell blowers (and the blower in the smuggler's box?). Search you will find many discussions on it.

I replaced the entire power front end main power harness on mine because of a dash BBQ like yours. Hopefully you haven't got too much damage. My damage amounted to the big red power wire feeding the tach and a bunch of feed and ground wires between the gauges.

timmy2 is the guy you want to talk to. He can repair/replace your harness depending on the damage.

G.
Old 06-26-2015, 09:40 AM
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Plug this into your Googler and be ready to read many posts on this topic:
dashboard fuse site:forums.pelicanparts.com/porsche-911-technical-forum/

Searching on interior lights fuse, dashboard smoke, etc. will give you even more reading to do. I'm not a big fan of electrical work myself but if you're methodical and logical you'll get it.

I too got that flash and puff of smoke once a couple of years ago - in my case, my headlight switch and ignition switch were OK but my turn signal switch, the high/low-beam contacts in particular, got fried. I installed headlight relays, a new turn signal switch and all the recommended in-line fuses that you'll read about in the many, many threads on this topic.
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Old 06-26-2015, 09:43 AM
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I had some smoke roll out a while back, turned out the P.O. had the wrong size fuse in for the interior light system. I had to replace almost all of the wiring for the interior lighting as it had melted down. A fuse is only good if it is of proper size to protect against the meltdown of the wire it's on.
Old 06-26-2015, 09:48 AM
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happened to me a few years ago and my problem was the ash tray light wire. the casing had dried and cracked in several places and eventually one of them grounded out.


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Old 06-26-2015, 10:32 AM
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Fusing.

Quote:
Originally Posted by gsxrken View Post
Got in my car and before I closed the door I had to throw some stuff in the back. Before I even started it, I started to smell and see white smoke from under the passenger glove box and saw the wires under the ignition switch start to smoke too.
Popped the bonnet to disconnect battery (with the tool kit tools) and saw the wire to my bonnet light in the hood smoking too.
Disconnected battery, pulled all nonessential fuses, got a cup of coffee nearby and reconnected the battery. No more smoke, and proceeded to drive home 3 miles.

Where would you start?? Why wouldn't a fuse blow?
Damn I hate electrical
Let's start by saying that fusing on the M/Y 911 & 930 was not Porsche's finest hour.

Here is the short list:





^^^^^
Based on you thread here is the most likely suspect.


^^^^^
If you don't want one of these.


^^^^^
Install one of these.


^^^^^
Also, prevents fires.



Fuse these.

^^^^^
Headlight relays are also well advised.

Good luck,

Gerry
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Old 06-26-2015, 11:07 AM
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I just bought an 87 g50 car with salvage title caused by a harness fire. Slightly more smoke and new harness needed. I'm gonna go new to avoid this same problem happening again.

Aren't u glad it was only a warning puff of smoke instead of reaching for the insurance agents phone number and 911? May be time to check whole harness to be safe. A lot wasn't fused like dash lights and headlights.
Old 06-26-2015, 11:22 AM
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A lot of good information here, guys. I appreciate the pics and the advice.
The last thing I want to have happen is to burn down this remarkable car. Not on my watch. I'm going to have to do some more reading and then dive in as soon as time permits.
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Old 06-26-2015, 11:36 AM
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Posting up some crispy wire. Now I need to search on how to remove the glove box so I can trace this wire...

the glove box light is all buggered:


The outside harness sleeve under the ignition key area also was smoking a bit and appears to have some damage. I haven't gotten into it yet
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Old 06-26-2015, 07:01 PM
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Looks just like mine did. take out your clock you should be able to see some of it. It will then run up into the frunk on the right side and power the light IIRC. Check your interior light fuse. I've gotta $10 says it's the wrong size fuse. I think it should be a yellow but don't recall what the amperage is.
Old 06-26-2015, 07:05 PM
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Quote:
Originally Posted by cabmando View Post
Looks just like mine did. take out your clock you should be able to see some of it. It will then run up into the frunk on the right side and power the light IIRC. Check your interior light fuse. I've gotta $10 says it's the wrong size fuse. I think it should be a yellow but don't recall what the amperage is.

LOL- I won't take that bet. Looks like there is 20-dog in that #4 slot. Funny thing is I would not have done that (seriously). I live in dread of car fires. But that means this fuse has been in there since 2002 when I bought the car... someone along the way must either have not had the right one or was experiencing a fuse blowing.


On edit- I'm going to review each of these for the proper size now.
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Old 06-26-2015, 07:14 PM
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Quote:
Originally Posted by gsxrken View Post
LOL- I won't take that bet. Looks like there is 20-dog in that #4 slot. Funny thing is I would not have done that (seriously). I live in dread of car fires. But that means this fuse has been in there since 2002 when I bought the car... someone along the way must either have not had the right one or was experiencing a fuse blowing.


On edit- I'm going to review each of these for the proper size now.
A lot of people don't understand that the fuse protects the wire not the thing the wire runs. A fuse is designed to blow before the amperage exceeds the meltdown point of the wire IIRC. You can stop a fuse from blowing by upping the fuse size but then wires start melting and eventually you either blow the bigger fuse or you have a reason to break out the fire extinguisher. I'd be looking at all of your interior light circuit wire if you can.
Old 06-26-2015, 07:21 PM
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Disconnect battery, remove gauges labeling everything, remove dash pad, remove glovebox, remove lower knee pads, become a contortionist looking at things from the trunk and under/inside dash. Etc.
you are going to need access to examine the entire dash area harness due to the routing of the wires that melted and may have damaged wires running with them.

Then it is decision time for replacing with new from Porsche or to have it repaired.

I replied to your PMh
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Last edited by timmy2; 06-26-2015 at 10:57 PM..
Old 06-26-2015, 08:59 PM
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You may be interested in upgrading to our replacement fuse panel. Takes blade fuses and has diagnostic LEDs and headlamp relays built in. Available from Pelican - click here

Some pictures:







More info on our website. www.classicretrofit.com
Old 06-27-2015, 01:52 AM
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You don't need to upgrade fuses, you need the right fuses in the right places. You also don't need to remove your dash panel to check out wiring. It's MUCH easier to remove the fresh air blower and ducting in the frunk and you can see every wire back there. I'd focus on your interior light circuit but definitely look for any other loom that shows a potential deformity. In my car the interior circuit was very well isolated. I had a near complete meltdown of my internal light circuit and all that needed replaced was the light circuit itself. I'm not saying that is absolutely the case with your car but the odds are good that is all that was effected.
Old 06-27-2015, 03:14 AM
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Electrical fires

Like gsxrken experienced, would give any owner a real scare, and it has for me 30
years ago on another classic.Since then every car i have owned has a battery cut off,
i switch it off every time the Porsche is left in garage,just a couple of turns and its off,
also if i park car away or over night,the knob threads all the way off to make the car safer from theft, infact i dont use the factory alarm on the Porsche, i still use heavy duty steering lock and remove the shut off knob,.But i can get that battery disconnected
in seconds, if ever a electrical short, and thats a must.

Old 06-27-2015, 03:52 AM
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Quote:
Originally Posted by wayne robson View Post
Like gsxrken experienced, would give any owner a real scare, and it has for me 30
years ago on another classic.Since then every car i have owned has a battery cut off,
i switch it off every time the Porsche is left in garage,just a couple of turns and its off,
also if i park car away or over night,the knob threads all the way off to make the car safer from theft, infact i dont use the factory alarm on the Porsche, i still use heavy duty steering lock and remove the shut off knob,.But i can get that battery disconnected
in seconds, if ever a electrical short, and thats a must.

Hey! Where did you get that? It looks pretty slick. Oh, and did you make that battery strap down setup? That looks like a lot less fight to get the battery out.
Old 06-27-2015, 03:58 AM
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Cabmando, battery shut off available all parts outlets and ebay .When my car arrived here to Australia it did not have a hold down on it, the previous owner fitted a battery that was a bit longer than stock and just left it.I purchased universal battery bolts available at
most parts outlets,and used piece of steel one inch by one eighth,painted it black.If you look down in the first photo reversed the battery clamp,drilled a hole in the top ,Done ok.

Old 06-27-2015, 05:19 AM
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