'70 Bus Wiring Mystery

[LittleTrainJames]

Hello Folks,

Been working on the wiring. Getting closer. Back turn signals are working, front, not so much, but getting there. The issue is that the wiring is 30% reworked with new colors and the schematic gives you an idea but no real clear answer. Lot's of trial and error.

Anway, I have two (don't know what the correct term is) connections on the top of my instrument panel, one says + and the other says G and then there is a 12v. What are these for?



I am assuming it is for the fuel gauge because that is what is up there, not sure though, the schematic I have doesn't address that.

Finally, I have this thing under my dash directly in front of my steering wheel. What is this? There are quite a few junctions (again terminology???) that pop up, this one seems particularly intriguing. Is this supposed to be there?



Thanks as always,
Little Train

[dtrumbo]

I am assuming it is for the fuel gauge ...

You are correct. The +12v is obvious and the 'G' connects to the sending unit in the fuel tank.

Finally, I have this thing under my dash directly in front of my steering wheel. What is this? There are quite a few junctions (again terminology???) that pop up, this one seems particularly intriguing. Is this supposed to be there?

It appears to be just a simple junction block. Is it supposed to be there? Well, it didn't come from the factory, but we'll let that slide. All it does is connect the wire on one side of the block with the wire on the other side. I see on at least the first two positions that there is a jumper to "buss" them together. That allows the red wire with the white inline fuse holder to be connected to two wires on the other side (obviously neither have anything connected). It seems this was a work-in-progress that was never finished as there doesn't appear there are any with connections on both sides. I hope this wasn't an attempt to bypass the original fuse box. That's still there under the dash on the left side, right?

[LittleTrainJames]

So if there are two connections up top and 'G' goes to the sending unit in the fuel tank, what is the other one for? Sorry, the obvious still escapes me

Not sure if it was an attempt to bypass the fuse box, it was there when I got it. Thanks for explaining how the 'junction block' works. The fuse box is definitely still there. The fun thing about it is that it was backwards and upside down when I went to work with it. Still is. Everything is correct, it is just in a different order. Regarding the wires on the junction block. I will check them tonight and explain where they all go and then maybe that can shed some light onto what it is doing. If my memory serves:

the blue and red wires on the left of the picture go to the fuse box on the bottom of it. The other wires, red, white, red go to light and emergency light switches. Like I said, I'll get it for sure tonight and get back to everyone.

Is it worth a new wiring harness? Is that too much hassle? Any good walkthroughs on how to install one?

Thanks for the reply. I appreciate it greatly.

Little Train

[sped372]

Just out of curiosity, what does your fusebox look like? It's very possible that someone swapped it with a different one because you originally had the crumbly yellow 1/2 year 1970 only one. They're not so sturdy.

From our late friend Karl:

1970 is 1970 only. Part number ends in a A. The early ones were yellow. They cracked down the middle. VW redesigned them with better material. It is white. Here is a yellow one, zip tied:



Here is the white one:



At one time, I had 3 of them for sale:



I do not know if I have any left...... I will have to look. A lot of stuff is packed away somewhere..... in my move from Fresno, Ca to Oregon.

Here are the fuse box numbers and what they fit:

Each year has a different suffix letter:
70 bus = 411 937 505 A
71 bus = 411 937 505 B
72 bus = 411 937 505 C
and if you are wondering about D and E:
73 411 = 411 937 505 D
74 412 = 411 937 505 E

[LittleTrainJames]

I definitely have the white one.

[sped372]

But from which year? Only the 'A' part is correct for 1970. If you have a later one you may have some creative wiring to sort out.

[LittleTrainJames]

I will check it tonight and report back. I assume I can see numbers / letters on the fuse box that will signify what year/model it is.

[sped372]

Yep, right there front and center. Look closely at those photos above and you'll see the 411 937 505x.

[dtrumbo]

So if there are two connections up top and 'G' goes to the sending unit in the fuel tank, what is the other one for?

The other connection marked +12V is for 12 volts which provides power to everything in the instrument panel. Originally it came via a black wire from fuse #9 in the fuse box. Your picture indicates things have changed.

Is it worth a new wiring harness?

As I understand it the "wiring harness" you can buy from the online vendors is just the wiring that travels from the engine compartment to the front of the bus. It does not include instrument panel wiring which wasn't in a harness per se anyway. Again, as I understand it, the wiring was all point-to-point in a haphazardly organized mess when it left the factory. Ideally you could rewire it in all the original colored wire but I think you would be better off to just make it function as original and not worrying about "restoring" it. If you have the later Bentley, the wiring diagrams are black and white. This one is a little nicer for visualizing.

[LittleTrainJames]

Cool, cool, cool. I have the black wire and I will get it up to that connector. Currently it is on the bottom half but not the top and some of the instrument panel is working some isn't. Maybe that is the issue.

Yeah, I would prefer not to do the whole wiring harness thing, better to keep it all Bad News Bears, more my style.

Thanks for the graphic, BumbleBus printed one of these out for me and I read it before I go to sleep every night. This always produces strange looks and hrumphs from my confused wife.

Again, thanks dtrumbo and sped372 for the replies.

[LittleTrainJames]

Interesting note. I was digging around Ratwell and noticed that the fusebox for the 1970 bus is backwards in the schematic.

http://www.ratwell.com/technical/Fuses.html#70

That makes me happy. At least I have a bit more faith that my fusebox isn't completely horked. Being able to trust what you have makes things a lot easier.

[dtrumbo]

I'm glad you got the fuse box orientation figured out. Typically schematics are drawn by electrical relationship and not physical relationship. The early-bay diagrams have some correlation to the physical layout of the components, but that was abandoned (I'm sure due to complexity) for the later bays ('73 on) when the current-track method was implemented.

[Amskeptic]

Note how there are insulated plates on the fuel gauge plate. Those plates each are energized with 12 volts positive through aforementioned black wires (from fuse #9). That means the voltage comes through the shells of the lamps that plug into them, like oil warning and generator warning lamps, and they ground through the center of the bulbs to the wires that lead to the engine. This is much more sensible to have those long wires leading to the engine on the ground side of the circuit. Thank-you.

(p.s. if the wiring is too customized, I would put in a factory-like color-coded proper harness. When you have an issue with wiring some night, it is nice to rely on wiring diagrams instead of the almost-impossible task of gleaning the intentions of some crazy home engineer)