more wiring questions!

[Andrew 777]

I have 2 more questions (for now!)
1 - There are 2 loose wires, the brown one comes from near the back of the voltage regulator - does any one know where it should go to? There is also a yellow wire in front which comes out of a cable with 2 wires, one goes to the top of the regulator, but the yellow one is loose - any ideas please?

2 - in the front luggage compartment near the fuse box there are 3 wires - one has a fuse connector, as shown in the photos. Can anyone tell me what to do with these please?

Thanks for all the help so far!

Andrew,

these are a lot of questions, not easy to answer just from the photos.

First I really would like to advise to study and compare the wiring diagram with the actual wiring in the car. To do so, you need a color print of the wiring diagram and you need wiring from which you are able to distinguish the colors. So, as with all work on your car, start with cleaning at least the area where you need to work. Clean the wiring - don't use an agressive solvent, remember the pvc isolation is 50 years old - and vacuum the working area. Only then you have a good starting point.

Some notes reagarding the pictures:

Your voltage regulator is not a the original Bosch type. It looks like a cheap China made replica. It's hard to tell from here if this one will work for your 912. Better to replace it for an original Bosch - much more reliable!

The yellow wire is the one you need to start the engine from the engine compartment for service purposes. It can be left loose.

Brown wires in a Porsche (Bosch) wiring harness are always grounding wires.

Your fuse panel also needs to be cleaned. Not only cleaned from dust, but also from oxidation on the terminals and contacts. The best is to rewire it, to prevent problems, specifically with the high current contacts (lights, motors, etc).

The wire with the fuse could be used to power a radio.


Some general tips:

- Try to find out why a loose wire was disconnected. Was/is there a short perhaps or is it just broken?
- If you don't have a multimeter, buy one. Even the cheapest one gives light in the darkness of flowing electrons.
- Reconnect and check the function of one wire at the time. It gives a better understanding of what you are doing and if a new fault occurs, it's easier to find its cause.
- Take your time. Faulty wiring can ruin your harness.

Your always welcome for additional questions to answer.

Otto

[Andrew 777]

Thank you for your help -it's much appreciated.
We did manage to figure out some of them and managed to get the licence plate lights to come on, and had figured out the brown was earth - still trying to get my head round the wiring diagram though!
Please could you tell me what the function of the regulator is? Do you have any suggestions of where I could get an original Bosch one either in the UK or US?
I will start with cleaning the wires and fuse box tomorrow!
Thanks for all your support

So going forward, step by step. That's great!

One thing I forgot to mention. The wiring harness in the 912 is the same as used in the 911 from the same year. The 911 engine had some electrical functions, not available in the 912. So the relevant wires are left loose. So don't worry if some connectors stay unterminated.

Well, I could write pages about just the voltage regulator and related components. Basically and simplified the voltage regulator manages the energy flow from the generator to the battery. A lead-acid battery as used in most classic and modern cars is quite critical in the way it has to be filled with energy. The energy source to fill the battery with the energy is the generator, a direct current (DC) source from which the voltage depends on the rpm of the engine. Without the the voltage regulator the battery would be shorted when the engine doen't run or runs at very low rpm and would be overloaded at high rpm. The voltage regulator keeps the charging voltage at the battery within a specific range. Again, a simlified explanation.

For parts I would recommend our host. They have a lot of parts and ship fast. Sadly, for European customers import taxes, shipping costs and VAT must be added, making parts from the US extremely expensive. Living in Europe, or specifically in the UK, there are some Porsche shops with a comparable range of products. I think it's not correct, as a guest here on the Pelcan board, to advertise with names of other suppliers of P-parts.

Living in the Netherlands I really regret not being able to support our host and buy parts from suppliers here in Europe for reasons I just mentioned.

Make some (close up) pics from the cleaned wires. It will be a lot easier to see what colors the wires have.

Otto

[Andrew 777]

Thank you. I'll be getting on with things in the next few days. I'll keep you posted and add new photos.

[Jaems]

I concur with Otto and he is very knowledgeable about these cars, however. There are members on the other 912BBS that are from the UK that can help you find the parts over there.

International

Also, if you can get the small 912 wring diagram blown up. It can help you to follow the wires without a magnifying glass. I have one that is 24"x37" or about 609mmx940mm. It is much easier to read.

[Andrew 777]

Thank you!

[Andrew 777]

Once I have cleaned up the fusebox, do you know if there is anything I can use to protect it and keep it clean and rust free in the future? Thanks

Andrew,

I support Jaems's suggestion to put your question regarding reliable shops in the UK on a local BBS. However, if you feel more comfortable here, you're welcome to join us. I live in the Netherlands and prefer the Pelican community, although I doubt if I ever will see the guys here on the board in person.

Back to your question. There are some protecting solvents for electrical circuits, but I personally never use them. You never know what theit influence on 50 year old components and materials is. The best way to keep your 912 in good condition is to keep it clean and in an environment with low humidity - in our climate not a condition which can be easily realized. Owing a 912 is always a balance between driving it and preventing it to be exposed to rain, salty roads during winter, too much heat from the sun and so on. Realize that in the end the corrosion will win. You only can have some influence on the moment the end is there.

Otto

[Jaems]

Bosch is pretty bad about corrosion with their wiring, the grounds especially. That is why you need to have a good wring diagram. The fuse box and grounds can be clean with rubber erasers.

If something electrical stops working. The first thing is to make sure the grounds and wring are clean to that unit. Then check the bulbs and the sending unit.

Always keep the fuel tank full if the car is parked or stored for very long. Even the wiring inside the fuel sending unit can corrode. You have to be very careful when cleaning them. They are only a hair thickness.

This bbs and the other 912bbs have some very knowledgeable members that know this cars. There is one on the 912bbs by the handle of 912UK (Mark) that is very familiar with the 912 and finding parts in the UK. There are a group of them that make runs over to the Continent for wine and etc. You can leave a private message over there to contact you.

Over here, you still have Otto.

[Andrew 777]

many thanks for that. I will try the rubber erasers - good tip!!

I have the wiring diagram, but find it hard to follow. Is the a colour code key that relates to the different coloured wires? Thanks

Andrew,

I agree with Jaems regarding the corrosion and storing the car. The only thing I would like to add is that I would remove the fuel tank in case you need to do a lot of welding on the car. At the other hand, the edges under the tank and from the tank itself are also very sensitive to rust. So good to take look overthere.

An alternative or addition to a rubber erasor is fiber glass erasor, used for erasing in ink based drawings. They look like a refillable pencil. Art work shops sell them. They are just a bit sharper and do a good job to clean corroded stripped wire ends.

The Bosch wiring harnesses are not prefect and like Jaems's note regarding the grounding sometimes frustrating. But ... who ever worked on French or British car wiring from the same period, will agree that the Bosch wiring is a journey in heaven compared to these vehicles.

Regarding schematic: basically you just have to follow a wire with a specific color from a to b. If a previous owner didn't attack the wiring harness with his elctric creativity to impress his/her friends, then the wire with the same color in the car will also lead from a to b.

Yes, there is a color code key for Bosch wiring in German cars, except BMW. Some examples:
Brown - Ground
Red - Battery
Blue - Alternator light
Signal lights - Black/green, black/white
Low beam - Yellow

And so on ...

This coding helps basic recognition of the function of wires in a harness, but that is all. For instance, a wiring harness is split in three main functional groups. These groups have their own main fuse, getting their voltages from three separate red wires from the battery. These wires are red because they are connected to the battery, but feed three different functional groups. So if you see a red wire in the harness, you need to follow it to make sure which of the three functional leads you see.

Again, you cannot work on the wiring without the use of a circuit diagram.

One thing which is important to know is that I'm not always available here. Sometimes on an almost daily basis and sometimes off line for weeks. But don't forget, you always have Jaems available, our 90+ hp 912-encyclopedia!

Regards,

Otto

[bfunke]

Andrew - you may also want to check out the 912BBS.