don't worry; I won't let it go to my head

I finally got the brake system warning light in my beetle back to something like working condition. In the photo below, I have turned the key to "on", so the two red warning lights at the bottom of the speedometer are on (left side of the photo). What's new is that the brake system warning light, which tells you if you have lost the fluid in one of the brake circuits, is now working and thus is lit up to test with the other lamps. It's in the upper right part of the photo, just to the left of the headlight switch.


A major amount of work to score a minor victory--but as a result there are several more electrical circuits on the car that I've crawled through.

Doctor Henry would be proud

One of the things about my Beetle that hasn't worked and really bugs me is the brake system warning light. I'm not sure why this has obsessed me so. It's a minor system after all. I guess it's a little bit like getting into playing Lemmings; it should be so simple, so you spend way too much time trying to make it work.

I placed a classified ad on the TheSamba VW site (a fantastic Volkswagen resource by the way), and someone taking a beetle apart sold me one. I didnt' want to go soldering on the only one I had. The light housing is basically a cylinder with the light at one end and connectors at the other, but here's what the innards look like:


Starting shortly before my car was manufactured, VWs had "transistorized" brake warning lights. The transistor is circled in purple here. I guess the improvement was that you didn't need to press on the light to test the bulb, instead the light comes on when you turn the key to "on", like the other warning lights. Unfortunately, it turned out that the components that formed the two circuits in the light (one for warning indication and one for power-on-test) were far less reliable than the bulb itself.

To fix it, I needed to figure out how it was supposed to work. With a magnifying glass and an ohm-meter, I figured out how the wiring was supposed to work. Here's a diagram for those of you into that sort of thing:


The labels in circles (15,K,31,V, and 61) are the labels on the connectors at the back of the warning light housing. Where I've labelled "tap" is a metal stud on the back that isn't meant to be hooked up in the car but is useful as a diagnostic tool when you have the light out of the car. (To keep this post blogg-ish, I will relagate the explanation of this circuit to my full write-up).

This was my reverse-enginneering of the bulb, but before I went soldering on stuff, I wanted to make sure I wasn't hallucinating. So I wandered down to Radio Shack and got a pack of NPN transistors and resistors suitable for duplicating this circuit. After reading on-line and resurrecting my dim memories of electronics class (1994-ish), I go this circuit to work properly.


Again, the transistor is circled in purple.

So I removed the old transistor, soldered in the new one, and hooked it up to the car, and it works. I'm currently in the process of getting the red lens for the light into a shape that will stay in the light, and then it will be done.

beyond the veil

I have some long-term work going on with the transmission linkage in my beetle


but I'm waiting for some parts at the moment, so I can't drive it, but I can't work on the shifter either. So I'm working on one of the very long list of electrical nits that need to be fixed. The brake warning light never has worked in the car. The light is at the top center of the dash board, which means that it's totaly impossible to get at the back of the light because it's obstructed by the combination of the radio and the windshield wiper motor.

So lacking anything constructive to do with the car, I'm try to get at that light, so that I can test it directly and check its connections. I got the wiper assembly loose, but it won't quite come out; the radio is blocking it. Here's the situation:


This photo is taken leaning over the right fender, looking at roughly the center of the dash board at the back of the luggage compartment. On the left is the glove box. Down at the right the gold thing is the outside part of the fuel level sensor which is in the top of the fuel tank. Most of the wiring is off the picture to the right. At the top center of the photo the grey cylinder is the wiper motor. Right below the wiper motor is the radio, which keeps the wiper motor from being removed. So I need to de-wire it and take it out.

I stopped there this evening, because it seems that the radio is spliced in:


Although--it occurec to me that maybe the beetles radios were spliced in by stock, rather than having connectors like the rest of the electrical system? Given that every other blessed connection in the car has a spade terminal, I would very much have thought that stock radios would have them too...but there's no reference to the radio in the wiring diagrams that I can see. So maybe the official installation method involved cutting wires.

So the next time I work on it, I need to document where those wires go and what they connect to, and only THEN take the radio out.

facinating...

I'm not going to claim that I'm the world's best documenter, or even that I'm a good one. However, my scientific training instilled in me a high regard for the integrity of documentation; if you make it, then it should be as close as absolutely possible to whatever it is that you're documenting.

And so it always facinates me when documentation is sort only sort of vaguely resembles what it is that it's describing. A couple of days ago I went looking for the wire that leads to be beetle's brake lights, so that I can measure the total amount of current that they draw. First, I found the relevant part of the wiring in the wiring diagram:


The important thing here is the three-wiring coupler. Generally speaking the wires going up on the diagram are going down in the luggage compartment of the car; most of the wires coming out of the top of that coupler go down to the pressure switches on the brake master cylinder. The wires on the right are black, indicating that they are at battery voltage when the key is on, but not otherwise. The black wire with the yellow tracer goes from the black wire to the horn.

I didn't include the whole diagram, but the black wire with the red tracer goes into the wiring harness and back to the brake lights. I've circled the wire in the diagram. I just need to find this connector, find the black wire with the red tracer on one side of the triple connector on the opposite side and opposite end as the black/yellow wire.

It is said that "theory and practice are closer in theory than in practice". No exception here.

To get oriented, here's where we're working.


This is taken from the right side of the luggage compartment looking across to the left side. At the upper right of the photo you can see the signal light on the left front fender. To the upper left is the brake fluid reservoir. At the bottom the black part is the left edge of the fuel tank. I've circled the triple coupler where it sits on the inside part of the fender. The wiring harness goes up to the left.

Here's a close-up, with my test lead already wired up.


The black/red wire is the center of the three, not one of edges. And interestingly, the black/yellow wire is on the OTHER side of the connector and goes into the wiring harness. I guess at some point they decided to connect to the + horn wire farther up the wiring harness, so it made sense to switch the side that the horn wire connected to, but that change didn't make it to the diagram.

So I found the correct wire, and I used the diagram to do it. However, whatever procedure was used to wire this car, the wiring diagram wasn't taken directly from it. By the way, the wiring diagram photo was taken from Bentley, but I did wander downstairs and double-checked the official dealer wiring diagram; it's the same.

By the way, the brake lights draw 3.87A at 12.7V. Plenty of overhead for an LED 3rd brake light.

it's only a flesh wound

I thought I was doing well yesterday. I had voltmeter and current meter set up in the beetle. I finished what I though were the final connections, and then I reconnected the battery ground strap. Big spark (meaning something's drawing a LOT of current). Uh-oh.

So it seems that the current meter that I have requires an isolated power supply--basically the "-" on the power input for the current meter is connected to the "-" on the sense input. Fortunately, the only thing I lost was the current meter.

Lesson learned. Before starting to hook a piece of electronics into any system, particularly your car, doubly particularly your vintage car, ask yourself "what happens if I hook something up ass-backwards and connect any random bit to ground?". If there answer isn't "a fuse blows" then you need to go back and re-think what you're doing. If I'd put fuses in the wires that brought the shunt voltage to the current meter, I wouldn't have smoked the meter.

So...I need an isolated power supply. This isn't such a terribly exotic device...however, its pratical availability in rural southeastern Kentucky is limited. I went to Radio Shack looking for something to use. Nothing, so I left the store degectedly. If I was a more patient person, I would have ordered an isolated-output power DC to DC converter and waited for it to arrive before shipping. However, I'm not a patient person in a certain mood, so I walked back into radio shack and got the parts for a simple, chemical-based isolated power supply:


It's a nine-volt battery wired to a 7805 regulator that puts out exactly 5 volts, which is what powers the meter. I brought the wires out through the front of the panel so that I can plug it in or not when I go to drive. This isn't the elegant solution I was envisioning, but it allowed me to get it going today. Pure stubbornness, in other words. :-)

Here's the luggage bay with everything installed.


The black box in the lower right contains the shunt. The bright red cable carries the main bus current. On the left side of the photo, you can see the two white in-line fuses in the shunt voltage wires to prevent any more mis-haps from mis-wiring. At the top of the photo you can see the backs of the meters through what was the speaker grill in the original design of the car.

What I've been working on. Huzzah! (Note the box at the very upper right of the photo; that's powering the current meter.)


The top meter is the voltage (in volts) at the main wire from the battery as it enters the front luggage compartment. The bottom is the current in amperes coming through that same wire. So effectively it's the voltage and current of the entire electrical system.

Now I can start using the meters to characterize the electrical system. A few preliminary values:
key on: 5.5A
key on + low beams: 14.3A
key on + high beams: 17.7A
key on + high beams + brake lights: 20.9A (at which point the votage has dropped to 11.2V)


The red lights to the right of the meters are the warning lights at the bottom of the speedometer. The generator light is mostly covered up by the steering wheel.

I also tried plugging in one of the halogen bulb sport headlights from Mid-America Motorworks. The headlight connector fit. On each low beam and high beam, the sport headlight drew about one amp more on one side. Not too bad.

By the way, I'd like to give a shout out to the outfit that I bought the panel mount meters from. Discrete panel mount meters seem to be going the way of the Dodo. They're very hard to find in even catalog stores. How I found an outfit called colfusionx who sells these and other electronics on ebay. The meters are cheap and they deliver the product as described. They don't send instructions, I guess they assume that you know what you're doing. (If I'd first measured the resistance between the terminals on the current meter OR had proper fuses in the shunt wires, it would not have been a problem). One thing is they have been VERY responsive to my e-mails. Twice I've written to them with a question, and someone got back to me within 12 hours. The most recent time was to tell me that "no, I can't use the current meter to measure its own poser supply, and yes that will fry the meter, so you have to use an isolated power supply" and that was what I needed to hear. So anyone reading this who's interested in panel-mount electronic meters, I would recommend these guys.

Incidentally, they also sell output-isolated power supplies, so I think I'll pick one up.

burble burble

My first real upgrade project for the beetle is to create a panel to the left side of the speedometer that has a voltmeter and ammeter for the electrical system. This will help bootstrap up to doing other electrical stuff. I started working on this panel the day we had people over to watch the Indianapolis 500 race.

Here's the back of the panel; I finished soldering tonight:


The power wires are on the lower and right side of the photo. The wiring convention in the beetle is that ground wires are brown, so I followed that. The wire with the in-line fuse brings in power. The other red wire is to power something else with the same switch that turns on and off the meters (GPS, maybe?). The wires in the the upper left of the photo are the sense wires that connect from the tap connections from the shunt. The wires with one connector each are the current sense wires. The one with the double connector is the voltage sense wire; I will connect it to whichever end of the shunt has the higher voltage.

After soldering everything together, here's a final hot test of the meters before I start installing things permanently in the car:


This is taken inside the luggage compartment where the wiring is. Notice the hole in the instrument panel to the right of the photo where the panel has been removed.

I made an enclosure for the shunt from a "project box" from Radio Shack. It should keep the shunt isolated from the car body. The heavy wires carry the current and the skinny wires are the tap that runs to the panel where the meter is.



By the way, after a second round of adjustments to the brakes, they're working very very well. On the first out-of-walking-distance drive, I noticed the steering wandering a bit. Not necessarily new, I just wanted to check it out. Well, there's a bushing in the steering system in the front end that I've ordered a replacement for. So I'm doing less driving until that comes, probably the middle of next week, and thus I'm working on system-level stuff.

did something right

While waiting for the front left wheel bearings on my beetle to dry, I cleaned the garage. In its 6-months-plus convolescence, things have become stacked around and under it:



Afterwards, much better:




You'll notice here that the right rear tire is on. Whoo!

Seeing as I more or less killed the already weakened battery earlier in the spring, I bought a new one yesterday, and topped off its charge:


in preparation for the big start.

As of this morning, the left front bearings and drum are ready to install:



Yesterday I adjusted the back brake shoes, and then I checked the emergency brake. I'm pleased to report that it's quite a bit tighter than it was before, which means that i did the adjustment roughly correctly and I didn't screw up anything in the emergency brake assembly.

It looks like rain today, so I probably won't be starting the engine until tomorrow. That'll give me the evening to get the car on its wheels and get the battery installed and all.

read the fine battery manual

By the way, do NOT deep-cycle a lead-acid car battery. I think that is an appropriate thing to do with some other rechargable battery technologies, but not lead-acid batteries. According the deep cycle battery faq on solar-electric.com,

Lead-Acid batteries do NOT have a memory, and the rumor that they should be fully discharged to avoid this "memory" is totally false and will lead to early battery failure.

So at the moment I'm trying to resurrect that battery, by running it part way down and then recharging it slowly.

darkest before the dawn

I have the battery out of my beetle to replace the battery cables, and while I'm at it, I'm going to recharge it, and clean out the bottom of the battery tray.

According to the hydrometer, two of the cels won't seem to I decided today to run the battery down to dead and recharge it; I seem to think that's good for lead-acid batteries, as long as you don't leave them discharged for too long*. I hooked up one of the sport headlights to the battery via some of the old brake cable hardware:



Tomorrow I'll recharge it and see if that makes a difference to those two cells.

*DO NOT DO THIS. This is very bad for lead-acid batteries!

wiring en passant

My beetle has been up on jack stands for four months. It's a good time to do a little battery maintainence, and I took some quick time yesterday and this evening to finish replacing the battery cables.

This is something that I've wanted to do since I bought the car. The stock cable that goes from the positive battery terminal to the starter input is black. That's not so bad, but at some point, someone replaced the cable from the negative battery terminal to the car's body with a red battery cable. So in other words, looking under the seat when I got the car, there was a black cable on the positive terminal and a red cable on the negative terminal, which is the opposite of most cars and any wire color convention that I've ever heard of. Not too long after I got the car, I replaced the red wire to the body with a ground strap, which got rid of the color problem but it didn't fit the terminal very well.

The other problem is the wierd right angle of the positive battery terminal makes it really hard to put a shield over the positive terminal. This is very important because the springs of the back seat can short against the positive terminal and start a fire if the terminal isn't covered.

I bought a platinum platinum positive battery terminal last week. This terminal has two pressure screw attachment points that accept a 4 gauge wire, or an 8 gauge wire with the reducing collar. The collar and one of the set screws can be seen in the second photo:





I've installed the new red cable to the starter and attached it to the terminal. The other attachment on the terminal goes to the electrical system in the rest of the car. I've also installed a black ground cable here whose end actually fits the battery terminal.

document faster

One thing I learned in graduate school is to take lots of photos of what you're working on. Even if the photo doesn't eventually turn out to shed light on what you think you were taking the picture of, sometimes something totally unrelated will be in view that's useful in some other way.

Working on my beetle yesterday, I was vexed that there are too many things in the way for me to get at the brake warning light, which is at the top center of the dash board and so is obscured from the rear by the windshield wiper motor and the radio. There's a bunch of wires that apparently go toward some of the switches on the dash, but I don't know which ones go to which, necessarily.

It occured to me this morning that I could actually count the wires that are in that bundle and deductively try to fiture out which wires are which. Here's the bundle:


Note there are two red wires, one bigger than the other, in this bundle, and a blue wire. Comparing that to this section of the wiring diagram that contains roughly the same wires (E1 is the lights switch, K7 is the brake warning night, E9 is the blower fan control switch and E3 at the bottom is the emergency flasher switch):


The only blue wire in this whole area, and one of the only two blue wires in the car, are in the group that go to the brake warning light, which is what I'm looking for. In fact, as the wires go toward the left side of the picture, there seems to be a separation between the fatter wires on the top and the skinnier wires at the bottom, and each bundle has a red wire.

Now there is one other red wire in the general area, which goes to the emergency flasher switch. As I look for the red wire that goes to the brake light warning, I need to make sure that whatever red wire I have isn't the one to the flasher switch. This shouldn't be a problem because both the red wire that goes to the lights switch and the one that goes to the emergency flasher switch connect to the fuse box, wheras the one that goes to the brake warning light ends up connecting to wires that go down to the brake master cylinder.

zen engineering

When you start working on something in a vintage car, you will most likely be doing something beneficial, but often now what you set out to do.

I worked on my beetle tonight, with the goal of testing the brake circuit warning light. I couldn't get to the back of the light to test it, but I did find out why the washers don't work.

Here's the back of the trunk before I started.



Now here's the same area with the ventilation box partially removed. Notice the end of the hose that I've highlighted at the left of the photo. That's part of the hose that delivers the fluid to the washer sprayer.



Now test the hose by pulling on the washer lever on the steering column, and voila! That's where the washer fluid was going:



I can't get to the back of the brake warning light just yet, but it's interesting to go through the wiring (kind of a rat's nest) and find the corresponding places in the wiring diagram. This attachment point is where a lot of the grounds connect to the body



And here's that spot in the wiring diagram



So I'm not going to be able to test the brake warning light at the moment; I'll have to find another way to get at it or at least its wiring.

until the paperwork is done

I finally found a program to create electrical schematics. It's called gschem and it's packaged under Ubuntu. That package seems to be a full electronic design suite, which I don't need, but it does make nice schematics.

I'm using it here to document the change I made to my beetle's electrical system yesterday. I don't have a driver's side door switch that works, and they don't make them any more. Here's the system as it's designed:


Notice that neither part of the upper part of the left door circuit is connected to ground. Notice also that the right door switch only has one contact, and that grounds to the case (which grounds to the door frame). The door switches are shown in the "door closed" position, and the ignition key switch is shown in the "key out" position.

To duplicate the functionality of the left door switch, I installed a right door switch (single pole, case-grounding only) in the left door switch spot, and wired in a relay to duplicate the double-pole isolating structure.


The system works, although there's a loud click when the dome light turns on when you open the driver's door.

energizer's bypassed like a Christmas tree

The volkswagen beetle, like any other car, has switches on the doors that turn on the interior light when the doors are opened. In the later years, the original beetle also had a buzzer that sounded when the driver's door was opened with the key still in the ignition. The wiring for this was a double switch in the door pillar that activated two different circuits, one to drive the light and the other the buzzer.

I've seen instructions how to dis-able the buzzer by pullout out the door switch, disconnecting the wires that control the buzzer, taping them up up and then pushing those wires into the door pillar. I don't remember where I read that, and I'm glad I don't. I don't know what kind of lame-brain would dis-able something in a car's wiring by disconnecting wires and then leaving them floating around inside the body, even if they're taped up. First of all, electrical tape comes off over time, and then you have a wire that randomly grounds and sets off the buzzer. Secondly, if you don't like the buzzer, why don't you, say, UNPLUG THE BUZZER itself? It's one of the three relays that are plugged into the relay rack right about the fuse box. Then you can always restore it to original operating condition by putting the relay back in. (And I'm not talking about vintage car issues; someone someday might own your car, and they might want to have it in original working condition.)

Ok, enough bitching. At some point, something must have been wrong with the double switch in my beetle (I don't remember now). I know that the buzzer wasn't working, so I think I pulled out the switch and was going to restore the wiring. Well, the switch was broken. I bought a couple of used switches at a VW show last year, and last night I went to install them. I started by fishing the relevant four wires back out of the hole in the door, which was no picnic:



I discovered that none of the switches that I had worked. I couldn't get a reading on them with the ohm-meter. You can't buy new versions of those switches as far as I can find. You can buy one switch that grounds a terminal to the car body when the door opens. But the way the buzzer is wired, that doesn't work, because the way the circuit is designed, neither side of the switch is grounded.

So I wired up a relay from a supply that I have around for just such occasions. This is a 3-pole, single throw relay, which is totally overspecced for this application but it means that I could do the job with one extra component. I soldered wires to the coil inputs of the relay, a short wire to go to the fuse box and a long one to go to the door pillar switch.



The left side of this photo shows an original switch (two pole, single throw, non-grounding) and the right side shows what I'm replacing the switch with (single pole, single throw grounding-only switch and a triple pole, single throw relay).


The setup on the right is big and cumbersome, but it works.

Here's the relay wired up and successfully tested. You can see the four wires that I pulled out of the door pillar and re-routed to plug into the relay.



The new grounding switch, wire from the relay attached, ready to install.



Door switch in and ready to go.



The final installation in the front of the car. The relay is duct-taped to the top of the gas tank, with a piece of cardboard for padding.


I wouldn't want to drive cross-country this way, but this is good enough to drive around town for testing.

Now there are definitely more efficient ways of doing this. The reason I used this monsterous relay is because I had it and it did the job all in one. However, two very small relays wired up together so that their coils were controlled by the door switch but they switched the two different output circuits would work just as well and be much smaller and easier to deal with, but I didn't have any more suitable relays in the house. The next time I get to radio shack, I'll pick some up and maybe improve this installation.

spaghetti blueprint

I'm becoming more and more interested in the wiring of my beetle as I contemplate launching into a project of adding gauges and electrical components and updating stuff. Before doing that, I need to understand the wiring as designed and implemented in the car.

As part of this process, yesterday I made a high-resolution scan of a copy of the wiring diagram for my car that I have. People have posted copies of the orginal wiring diagrams, but I wanted higher resolution versions, so that I can post modified versions.

Here's the main scan (reduced in resolution, of course):



One of the diagrams I wanted to produce was to highlight the wires in the car that are live, connected to the battery without fuses at all times.
Here's a partial diagram of the fuse box. Note the red wire that I indicated with a purple arrow. That's the main wire directly from the battery.



The other two red wires shown here are connected to the main battery wire with a metal strap, all on the unfused side of the fuse box.



Here are the actual wires in the car:



This diagram shows where those wires go in the car. From the fuse box on the left of the diagram, one red wire comes through the wiring harness from the battery that's at the right of the diagram (in the rear of the car). One red wire goes up to the light switch, the other goes down to the ignition key cylinder switch.

Be patient; I'm pushing a large RV!

My beetle has a tow hitch attached to the front suspension and it's wired to be towed as a trailer. I'm suspicious that this has impacted the wiring. One of the issues is that when I push on the brakes, the speedometer illuminator light comes comes on as does the lights on the front fenders. The other wierd thing is that one of the tail lights (and brake lights) is brighter than the other one.

In the process of thinking about this, I wanted to know what the connections are on a trailer plug (the wiring that goes from the towing vehicle to the trailer to make the trailer's lights work). I did some searching to find the wiring diagram for a trailer plug. I knew about 4-pin plugs, but apparently there are also 6 and 7 pin plugs. I didn't find one page that had good diagrams of all the different types, but I found a few pages that cover all of them.

• good 4-pin diagram
• plan-view diagrams; good 4-pin diagram
• good 6-way and 7-way diagrams
• good 7-way diagram

I'm just collecting these diagrams together for reference. This has been a public service message. :-)