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Hi anybody,

I bought a 1973 VW bus a few months ago and I've been going through the wires in the engine bay (really not pretty). I'm considering just buying a complete new wiring harness, can anyone tell me if this is a good/terrible idea?

If it's a bad idea, I'll keep working on the wiring myself... I've been looking through the post that contains all the schematics/wiring diagrams and they were really helpful. My problem is that I don't know very much about wiring, and I'm not quite sure what I'm looking for/ what the loose wires in my bus actually correspond to on the diagrams.

For starters, can anybody tell me what this is/what it goes to? it's that beige wire:
Or what these hook up to? Thanks for the help!!

Rewiring a VW is a fair amount of work, but if you do it, you'll have that rare and precious thing, a VW with no electrical problems. I tried to fix the wiring on my 74 bug so, so many times, with limited success. Once I installed a rebuilt harness, it worked like a dream.

Do you know where the other end of that cable went? I don't recognize the three-position plug, but I haven't had a baywindow for many years - the connectors at the other end are the usual VW connectors. Do your brakelights and backup lights work? Those connections are usually found on the left side of the engine, at least with bugs.

Stray

I'm certain that some of the loose wires were not part of the original design. That is the joy of experts over the last 40 years or so.
Diagrams like http://www.vintagebus.com/wiring/bus-73-75.jpg are useful when stock, but you must start tracing back what you have or even worse what has been re-appropriated. For starters your bus had a mechanical driven fuel pump, so the electric driven pump you have now is on no chart.

First rule of troubleshooting, what is it plugged into?

3 prong plug goes to the flywheel sensor in the bell housing.

Thank you all so much for the help! This is more info than I've had in a while

So Stray, do you recommend buying a whole new harness? It just sounded a lot safer to me...I think I'd rather do that than try to untangle the mess I have here, if it worked out well for you. (Though now I'm concerned about the electric pump, I'll have to do some additional wiring on my own to get that hooked up, since it's not the original?)

Currently the only lights that don't work are the back-up lights. I've found the fuse, and may replace it for good measure, but I know it's not the bulbs and everything seems to be connected OK otherwise. If the fuse and the connections are fine, would that mean the switch is the problem?

Thank you for IDing that 3-pronged plug! It was not plugged into anything (as is the case with many of my wires). It disappears in the middle, sort of, but i couldn't tell if it went through the wall or not. So flywheel sensor belt housing, how important is that/anybody know the actual physical location where it plugs in? I couldn't find a socket for it.

The problem with the "what is it plugged into" question is that most of the time the answer is "I can't tell". A lot of the wires just disappear through the firewall in a massive clump with several other bundles that are often very close in color. I've gone underneath, and obviously it's all packed up in a nice neat little package to protect it, which means I can't see individual bundles.

That makes a lot more sense knowing that my electric pump is not on any diagrams. I figured that a lot of those wires were not original, just had no idea which ones or how many..

Thanks again!!

Rewiring is a LOT of work, but tracking down every individual problem can be heartbreaking. If the only problem you currently have is lack of reverse lights, hook a switch on the dashboard to operate them, and get your bus inspected by a mechanic who isn't looking to screw you over.

Many (all? not sure) of the VWs in the 73-74 era had a "diagnostic plug" in the engine compartment - a white plug about the size of a hand grenade, with dozens of wires leading to it. Dealerships had the specialized equipment to use to plug to find out a number of things about the vehicle, it was the neanderthal great grandfather of the OBD stuff that all cars use today. It's unlikely you'll find a way to use that plug, and many people just cut it off - so if you find a bundle of wires that end in the engine compartment (on the left side of the engine, usually above it) don't panic.

The backup lights should be connected to a spade terminal on the front of the trans, it's not too hard to find if you're under the middle of the bus with only your feet sticking out under the rear bumper. The dashboard switch is good enough, but use a lighted switch so you don't forget to turn it off after you shift out of reverse.

Stray

Yeah, it's been a little heartbreaking, which I think is making me lean toward an entirely new harness -- the reverse lights aren't the only problem. Others include the charging system (haha, I can't even get it TO a mechanic for inspection), the defroster, the heat... And sometimes one of the brake lights goes out or gets a bit flickery, but the bulb is fine, so I'm assuming that's a weak connection somewhere.
If I thought it would pass any inspection I would just put a bunch of switches on the dash, but it needs a fair amount more cleanup than that. (Also, a lot of these wires look like they'd disintegrate if I touched them too hard, and I'm loathe to leave random cables lying around if I don't need them or can't figure out what they were once used for.)

Rewiring is not something I'm particularly dying to do, but I'd almost rather deal with the work than with the mystery of what's been done to this poor bus in the past 30 years. I also figured that if I were forced to rewire the entire thing myself, I would then know a whole lot more about my electrical system and (hopefully) run into fewer problems later? On the other hand, I run the risk of getting a huge octopusy wiring harness in the mail, and then being totally unable to hook it up properly. Guess I'll think a bit more on that one. Can I ask how long it took you to rewire yours?

Good tip on the lighted switch for the reverse lights I had considered installing a button, but hadn't thought of that... I can picture myself going down the highway with the backup lights on the whole time, that'd get me pulled over fast.

I believe I may have one of those white plugs. Snip, snip, one problem down. Thank you

If you cut out that plug, make CERTAIN to isolate the wires - some of them are live, others are sometimes live, all of them can spoil your whole day. If the plug is there, it's not doing any harm, so I'd recommend leaving it. I rewired my bug in a couple of weeks of evenings after work, though a good mechanic with a garage could probably do the same job in a day or two. Get a wiring diagram and learn how to read it - German engineers were compulsive about following color codes, and it'll save you a lot of pain and confusion when you learn that black wires are NOT grounds in a VW...
Your brake light may be a ground issue, bus brake lights are infamous for that. Clean up all the grounds for all of the lights and that problem may go away.

You don't need to connect anything to the 3 prong plug. It can be used to set timing and for diagnostics.

Thank you for the warning about the plug. Wouldn't want anything to fry.

If I do decide to re-wire, does anybody know, is this what I need (Central wiring harness)?
http://www.busdepot.com/details.jsp?par ... 211971028M

And I need this (the alternator wiring harness) as well?
http://www.busdepot.com/details.jsp?par ... 021971349F

I've been hunting around on Bus Depot, and there are all sorts of wiring components offered... spark plug ignition wire sets, for example... anybody have a recommendation on what to start with?

From the pics, you are a LONG way from needing a new harness.

If you think THATs is a lot of wiring, you have never seen a fresh harness ... before installation.

Wiring is actually pretty simple...

Fixing it, use the same approach as you would eating an elephant.
do small sections at a time, once circuit at a time.

But a GOOD set of ratcheting crimpers with replaceable jaws, they should last you a lifetime.

I've somewhat regularly started going to the junkyard to pull old harnesses from Buses & Bugs - It's amazing what you get for $10 or $15...Maybe you could do the same to familiarize yourself better and have some spare parts need be?

Bus wiring is SUPER simple to pull out - the whole main loom runs through a conduit below the bus...cut and/or disconnect everything at the dash and you can pull it out from the bumper in minutes.

With a test light, multimeter, the ratcheting crimpers, and some quality wire strippers you can square things away pretty easily - albeit fairly time consuming. Dielectric grease, sandpaper, solvent soaked rag for cleaning insulation, and a media blasting cabinet also come in handy.

Many a skilled mechanic don't understand simple wiring, it's a process to learn, ask questions.

I like the junkyard idea, that sounds waaaay cheaper. Thank y'all for the tools list, I'm definitely missing one or two of those that I hadn't thought of.

Piledriver, I know I could fix each individual problem, but I'd almost rather take everything out and re-do it myself, because I don't know how many other problems are lurking around in there, and I'd like to know my electrical system better... I feel like I'd learn a lot if I replace the harness, and be more comfortable working on it in the future, plus all the wires would be in better shape. I'm not decided yet, but leaning toward rewiring. I like the elephant metaphor (:

I spent a few months trying to track down individual problems before I gave up and replaced the whole harness - but this was after a serious electrical fire under the back seat that destroyed every wire from the back seat to the engine compartment, it wasn't just corrosion and old age. Electrical systems are elaborate collections of simple connections - any one, as an individual, is a trivial problem to fix, but as a pile of problems it's overwhelming. The elephant analogy is a good one. Something else you can try - if you get one (or more) of those junkyard harnesses, you'll have the experience of removing them, and all the connectors you need to repair yours.

I'm liking the junkyard idea more and more... thank you all for the input, I appreciate it. I think I'm going to go with a new harness for safety/learning's sake, since I have the time to. Ciao!