Electical Issues

Hello I recently bought a Euro 71'T with multiple electrical issues. A little back ground it that it now has a 74' 2.7L engine and it has been switched from dual batteries to a single. There seems to be unattached wires everywhere.
My two issues I was hoping to solve first are my tachometer is not working (it lights up when I turn the lights on). Second when I use my turn signals both signals in the tachometer go on. And when I hit my brakes the signal lights in the tachometer light up solid.
Any help or at least where I should start looking for these issues would be great. I have a Haynes repair manual but is there anything better then that. Did Porsche make a legend of what color wires normally do what? I heard that brown is always ground is that correct? This is what my fuse box looks like are wires suppose to be exposed like this? Does anyone know what they are for?
Thanks in advance Many Many more questions to come
Attachment 302341

WELCOME to the forum.

Let me get one thing of out of the way. . . diagnosis of electrical issues is difficult enough when you are standing next to the car with a meter in your hand. Over the Internet it's tougher. . . and made a lot worse if prior owners have changed the wiring to non-original, such as what may have happened in the case of your 2,7 swap. So it's going to take a lot of clear photos and explanation of what you actually have in order to make progress.

Next: primary sources. There is nothing better than the Factory Workshop Manual (FWM). See if you can score one in the classifieds used by putting up a WTB. That will cover all the basics for the car itself. The Haynes manual is not very good, the Robert Bentley is better, but it's not as good as the FWM.

For electrical you are in luck the original wiring diagrams were in the back of the owners manual, and various sources have them available online. Download them, print them out on 11x17 color paper and spend some time relating what you see in the car back to the manual.

The best source is here: http://members.rennlist.org/911pcars/WiringDiag.htm

and as an alternative here: http://www.pelicanparts.com/911/911_...l_diagrams.htm (click on the both 1971 diagrams and the legend).

Next, to your specific problem. The way the factory designed the flasher circuit, it will illuminate both bulbs when there is a problem in the circuit. The first thing you should do is take out the turn signals, very carefully, verify that the correct wires go to the correct terminals, clean all the oxidation off the contacts with a piece of emery paper until they shine bright metal, then reassemble with the correct bulbs. This is a key step in solving your issues but it probably won't solve them all- you may need a replacement flasher unit. Replacing the flasher MIGHT resolve the issue with the brake lights.

Hitting the brakes and having the turn signals light up is a more worrying issue, it's evidence that somebody has cross connected the brake light circuit. And that forward fuse panel needs some help. The wax thread to hold the wires together is original, it was just concealed underneath the factory PVC tubing that usually covers the harness up to that point. See the black wire with green stripe? that is, for example, the wiring for the car's starboard side turn signals.

First, disconnect the battery. No kidding, if the battery is connected with the wrong wiring connections you can short out wires immediately, burn the car down or worse. . . if you are not 100% positive of the connections you should seek the advice of a professional.

With the battery disconnected, carefully inspect and photograph the wires that are missing off the fuse block. Also, there are some relays and additional wires up under the dash by the gauges, and at the electrical console in the engine compartment. You want to make sure there are no loose wires hanging around that could short to the body sheet metal when you switch the power on.

This should be a good start toward finding out what you need to do. I would start by checking the turn signal connections and bulbs themselves, then work out from there, checking as you go.

Another tip from long experience-- don't use anything stronger than P21S total auto wash to clean the overspray and dirt off the wires for identification. If you use a solvent it will remove the tracer from the wires and you won't know which is which!

It's a lot of work, but if you follow the diagram exactly and work deliberately you will get there.

Good luck! There are lots of resources here to help.

And WELCOME.

It will take some time to get the wiring straightened out. The engine swap will not affect the chassis wiring. First thing will be to get the wires on the correct terminals on the 2 front fuse blocks. The Pelican link above will help identify some of the wiring. One of the things to understand is the diagrams are a mirror image of the actual wiring. Here are a couple of pictures of my fuse blocks and some reversed images of the wiring diagrams.
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more tips - put elec. tape over the end of every bare or cut wire now to eliminate shorts later

after you disconnect battery while tracing, you can connect in a small 9V battery for testing of most things to prevent dangers from major current flow

strong vinegar will clean corrosion off of connections, though yours look clean - I also use an electronic contact cleaner after the vinegar - and as a preventative

Yes, brown = ground - clean all ground connections - take them apart & do not rely on a mere view of the outside

brown/white, etc. means the wire is switched to ground

there is a DIN chart of all colors somewhere - the Germans have everything spec'd out

watch for an alarm or something messing things up

Sadly, a wiring hacker of a PO may well have done other damaging things as well, maybe imperiling the safety of the car - it can all be fixed, but watch carefully for anything odd looking

Good Luck!

WOW! Thank you 37yrold911, ESully and 304065 for the great advise, links and diagrams! This will give me a good place to start.
I am sure I will be asking for more advise soon but this should keep me busy for a few weeks

One of the great things about the early cars is that with a color copy of the factory manual workshop wiring diagram, you can literaly trace each wire and circuit. Makes them fun to work on.

The tachometer lighting, black/blue from the light switch, is separate from the indicator needle. You should have a red/black, black/violet, brown on the strip on the rear. Can you post a picture of the back of yours?
The 3 black/green wires hanging loose should be on fuse terminal 10. The wire going to the right front directional should be on the left side of the fuse, and the other 2 should be on the right.

Usually the reason for someone to remove those wires is they have a serious short occurring at the light unit. So use caution when you hook it all back up.