There are no "keys" per say.
The top of the page is the Positive current paths.
The Bottom of the page is the Negative or ground path.
The Bottom of the page has numbers that correspond to the index in the front of the section.
If you have a diesel then you have a gasser manual and that won't work.
If you have a gasser then you have to look for the year 1980 vw rabbit/truck
From my electric primer...
What are all these squiggly lines?
When you are reading schematics there are symbols and things that look like they were drawn by some dudes that were smoking refer. In reality I think that they were as when you are talking about Electronics and you are deep into it you are in another world. The history of the men that formed the basic principles and discoveries are really fascinating reading.
Gallenium Silicon,
strata, emitters, base, collectors, windings, current, voltage leading current, uni-junction, propagation, array 's, are all terms that are familiar to some and out of the world to others. Welcome to my world, most all Techies that I have meet who like me were or are currently designers of circuitry revolve in our own little world we look at a circuit see the symbols and convert it to a jumble of mathematic equations. Electronics is Math, Physics and Chemistry in its truest sense. There are rules that were laid down for a hundred years by brilliant men and these rules govern every thing that a circuit can do. And you wonder why you can 't make heads or tails out of it? Most of the original work developing circuitry was by folks like me with Slide rules and pocket protectors, there weren 't calculators, and computers that fit on your desk took up buildings.
One of the first mass produced computers didn 't go to a bank or credit-card company, you found them in bars, yes that is correct one of the first mass produced computers were simply a PIN-BALL machine . Ever looked inside a vintage 50 's unit? Relay-Relay logic, switches inductors all kinds of neat crap, don 't think it 's a computer, well for a given input (the ball) it adds subtracts divides and multiplies depending on the input (how many bumpers the ball hits and when). So see your Greaser father in the love of a PIN-BALL machine was the first true Gamer.
Well enough about the history lesson lets get down to it.
There are basic fundamental rules that are laid out and I will re-iterate them for you, they are written in stone, and if you accept that then you will have a fun time
Voltage expressed as E voltage is felt on a circuit path.
Current expressed as I amps flows through a circuit.
Resistance expressed as R in ohms opposes both current and voltage
Power expressed as P in Watts is equal to Current times Voltage
E=IR there are variations to it as n E/I=R
P=IE
Let 's take a light bulb that is rated at 100 watts running at
110vAC
since we know that P=IE we can figure out the current of the bulb
100/110 = .9090909 Amps of current.
Now that we know the amperage of the bulb let 's find the resistance?
E=IR so E/I=R basic substitution
110/.9090909=121ohms of resistance. In actuality the bulb is a Inductor, and that the impedance is really the true measure of the resistance value, but you can get the general Idea.
Ohms laws are the founding principle and you can't get away from it.
Everything in a circuit acts as a Resistor in the simplest form.
LED 's, Transistors, relays, switches, capacitors, motors, and all solid state components in a circuit act as variable resistors.
I am not going to expand on this any more, if you want to know more there are volumes of material available on the WEB or from your library that will tell you everything that you want to know or more take it as a given.
Basic 's
The introduction in the Bentley is wrong, they tell you that current in a circuit flows from the positive to the negative, that is the way it was taught in the 50 's, and early 60 's, now that science had accurate ways of measuring the flow of holes between electron, they discovered that in fact current flows from the negative to the positive.
When you are reading a schematic (fancy term for wiring diagram), you have to remember the orientation of the page.
Rule number 1. All pages orient so that ground paths are at the bottom and supply voltage is at the top
Rule number 2. Current flows in a circuit from the ground path back to the supply path.
Rule number 3. All switches are usually shown in the off position, unless otherwise denoted.
Rule number 4. The bigger the wire or resistor the more current it can take, the more current that it takes means that they can get hot and burn your ass if you touch them.
Rule number 5. All tie points in a circuit are denoted by a blacked dot at the
cross point, if it doesn 't have a darkened dot then it is not a part of the circuit that you are tracing.
Rule number 6. A failed component will cause an interruption of current flow from the ground path to the source.
Rule number 7. Fuses go, and a visual check is not the answer, you have to test it by resistance checking or by voltage testing. Yes you can usually see a
30 amp fuse that is blown, but the .5amp ones are very hard to see.
Rule number 8. Replace the fusefirst before going on.
Rule number 9. NEVER OVER FUSE A CIRCUIT .you will find the problem child, but you can burn up half the wire in the car doing it.
Rule number 10. If you are measuring the voltage at a solid state component, and you see 12Vdc on one side and 11.5 on the other, all that means is that the circuit is probably working, as it takes but a small change in voltage to turn on a solid state component. Don 't be fooled .lord know I have from time to time.
A circuit that has a .5amp fuse can KILL YOU if you become a ground path.
Direct Current will stop your heart, cause you burns, and can generally ruin your day. Be careful the Average Battery in a car has 600 amps of stored energy waiting to sneak up and smite thee in thy arse. I wear
latex gloves when playing with electricity .
Series circuits are designed so that a break in any of the components stops the whole show think of a string of
Christmas Lights.
Parallel circuits are designed so that a given component can fail but others continue to function as needed think Light Bulbs in your house.
Expanding on Rule number 6, if a component fails, it can fail two ways Opening, or Shorting. If the fuse is good you can back track it to see where the ground path is lost by seeing where the voltage is present by jumpering it to ground with a 12volt test light to ground. This is a handy little bit on knowledge that I am imparting to you. Once you have found where the light stops in the circuit by dividing it up in bits you have found your failed component.
If the Fuse has failed and you replace it and the fuse blows again you have a circuit that is shorted from the Source directly to ground. You have to start disconnecting things to find the failed component, it is simple to do, knowing the path that the current has to take allows you to measure resistance to find the trouble spot.
When reading a Bentley or a Haynes, the engineers at VW who drew them out originally graciously labeled all the components and color coded the wires so that is a big help to the average reader, as the original VW mechanic has little if any electronic training we will expand on them a bit as needed. From reading the previous pages you probably know more than most of them already. You don 't want to know about how airplanes wiring are all the same color white, but they are numbered ..
Wiring paths can change colors; from red/green tracer (little green line in the solid red wire) to a white/blue (solid white wire with blue tracer) the second color always denotes the tracer. You have to be cognizant of the wire colors at all times as you may start tracing the wrong path. Wherever the color changes there has to be a connector. This is one reason that most companies including the Armed forces will not hire you for certain jobs if you are color blind ..
Reading a wiring diagram is a lot like a topography map, or a travel map, you have to zero in on the route that you are following to get from a point to your destination.
I will start by referring to a page in the Bentley, and I will give you the same page number from the Haynes Rabbit book, this way every one can follow along no matter which book you own, the books are:
Bentley Publishers
œVolkswagen Cabriolet, Scirocco Service Manual 1985-1993
Haynes Publications - 96016
œVW Rabbit Golf, Jetta, Scirocco, Pick-up 1975-1992 All gasoline engine models
Are we READY? Got your Haynes or Bentley out? Lets all start by turning to page,
Bentley Main Wiring Diagram Cabriolet 1985-1986 page 4 of 5
Haynes chapter 12 Chassis Electrical Systems 12-90
We will be talking about the Windshield Wiper Circuit so that is on the left hand side of the Bentley
The years are not the same but the circuit is, and that is what counts for this discussion
On the page we see a lot of information let 's start by orientating the page 's information.
At the Top of the page we see all the source paths for 12Vdc. we can see the fuses that are in the circuit and the intermittent wiper relay. All those lines are on the fuse panel neat.
The middle of the page contains the Wires that are running through out the car from the fuse panel to the various components.
The bottom of the page has all the ground paths for us, cool isn 't it.
Lets Look closer at the books, do you see the difference if you have both open to the same pages?
The Bentleys are photocopied from the source and were never cleaned up, the Haynes are a sharper copy that they took the time to clean up . Who copied whom? The Haynes has a typo the backup light switch isn 't in the water temp gauge path? Nifty, so for sake of reading the Haynes is a little cleaner, but the Bentley ties the pages together.
When you are reading a diagram, you have to think that you are in the circuit traveling through it in the most logical path to get the source, with that being said we have to start at the ground path and work are way up the page to the source.
At the extreme bottom of the page we see that there are little numbers those are the ground path number also the current track it is also a reference number that may take you do a different part of the circuitry to another page. If you go to the index, for the main page on the Bentley and look up the windshield wiper motor, it will tell you that it is in the current track of 105-106, quickly you can follow the numbers on the bottom of the page and when it gets to 105-106 look up and you will see the windshield wiper motor.. but is doesn 't have a path to ground, so why did they say that it is at current path 105-106 .because they are using the current paths as an INDEX so that you can locate things quickly.
The top of the pages have the source paths for us those are common bus points that follow from page to page
The index page of the Bentley for the Main wiring diagram tells us where stuff is located in the Diagrams, tells us where to look for things, as different Grounding point and where various connectors are located in the dash on the firewall all kinds of neat stuff s there . The Haynes book is a little devoid of that information, but they list the things covered at the bottom of the page.
Every relay that is on the fuse panel is always shown at the top of the page in the source path bus 's .
So let 's see what it is telling us first that the ground is on current track 16 and if you follow that all the way back to the origin you will find that it is in a tapped wire loom in the dash.
So looking at the circuit we start at 108 and come up the page in a brown wire to pin 31 on the column of the Steering wheel where the switch is located, from there it stops, why because the switch is in the off position doh
Let look at what all the pins of the switch are doing at rest/off then on Low then high
We have to build a truth table to help us all that means is that we need to know what the pins are doing at every selection.
Motor pins
OFF Pin 53 and 53a have no voltage
Pin 53b has 12VDC
Low speed Pin 53, 53a, 53b all have 12VDC
High Speed Pin 53 has nothing
Pin 53a and 53b have 12v
Steering Column Wiper Switch
Off 53 and 53e are mated
Low speed 53 and 53a are mated
High Speed 53a and 53b are mated and 53a 53 are mated
Intermittent 53a and J are mated and 53e and 53 are mated
Washer 53a and T are mated
Now if you are wondering what the switch is on the Motor that is the parking switch that returns the motor to the stopped (rest) position if the blades are up when you turn off the switch, as long as it is running there is nothing that the switch really does.
So we have our truth table .
At the bottom of the motor, we have pin 31 that is actually the ground path for the motor, and when we operate the switch he are providing 12VDC to the motor through the pins 53 and 53a and 53b to make it spin fast or slow or intermittent.
With the switch in the first on or slow setting 12VDC is supplied from the fuse at S11 it goes down the page to pin 53a of the
motor parkingswitch.
12VDC is also supplied from the fuse at f11 down the page to the tie point.
Then to the left to the tie point from there it goes up the page to setup the 12VDC on the pick side of the intermittent relay and then down the page to pin53a of the switch. since pin 53 sets up the 12VDC to the bus at the switch, there is now 12VDC on pin 53 which goes up the page and to the right and through the normally closed section of the intermittent relay, but also sets 12VDC at the bias point of the solid state device backing though the normally closed portion of the intermittent relay we go down the page then to the left then down the page to pin 53 on the motor, turning on the motor. As the motor is spinning about it opens and closes the switch at 53a and 53e of the motor.
Wow all that just to get the
Motor turning .
Now we are going to move the Switch to the High speed side.
With the switch in the first on or high setting 12VDC is supplied from the fuse at S11 it goes down the page to pin 53a of the
motor parkingswitch.
12VDC is also supplied from the fuse at f11 down the page to the tie point.
Then to the left to the tie point from there it goes up the page to setup the 12VDC on the pick side of the intermittent relay and then down the page to pin53a of the switch. since pin 53 sets up the 12VDC to the bus at the switch, there is now 12VDC on pin 53b and 53 here is where it gets a little sticky.
Again
Pin 53 which goes up the page and to the right and through the normally closed section of the intermittent relay, but also sets 12VDC at the bias point of the solid state device backing though the normally closed portion of the intermittent relay we go down the page then to the left then down the page to pin 53 on the motor, turning on the motor.
And now 12VDC is supplied to pine 53b that goes up the page to the left then down the page to pin 53b adding an additional current path to the motor.
Since the motor has two separate sets of brushes and windings and that the total current available to the motor is set by the fuse @ no more than 15Amps we have just kicked the motor into high gear. The more windings that the Motor has the faster it can spin, on low speed it is using one set of windings now with the switch on high we throw in a new set of windings. Since the motor is now getting voltage and current at 90 degrees difference instead of 180, it starts to spin faster.
Now when we turn the motor off and if the blades are not at rest, the parking switch which is normally open is now closed and we know that pine 53 and 53e are mated there will be 12VDC available to the motor until the parking switch moves from pin 53a and 53e on the motor, once that happens the motor will stop and the blades will be parked.
Now when you place the lever in the down position, intermittent you start to engage the intermittent relay. Think of it as a having a little person inside of it that is counting to two and throwing the switch from on to off.
Basically it goes like this. take a breath.
We know that there will be 12VDC at pin53a pin 53 and 53e and now there is 12VDC at 53J
So the normal low speed part still works and is there spinning the motor, but a timer circuit starts to activate (a 555 timer is actually the chip and a capacitor). Because pin 53e is at ground from pin 31 of the motor the minute that you press the switch down you charge a capacitor in the relay. (This actually happens every time you turn the switch on.) Since the motor is starting to spin the motor park switch closes to pin 53a an 53e are together once the motor get fully up, then down, the timer is starting to count a one and a two, that energizes the relay providing power to the motor to sweep for a two count up, and down wait 2 then up and down. Wait The charging of the circuit some times gets a little off, corrosion of the contacts, a sticky relay, a timer circuit that didn 't get fully charged is why sometimes the count is off or the motor stops mid way.
The windshield washer circuit basically does the exact same as the intermittent but there is a longer count to hold the motor on. The counter doesn 't start until you release the switch.
There are a lot more things that I left a little froggy here because of the nature of electronics.
Why does a motor spin? Windings? 4 instead of two
But basically you can now read a simple current path and know how to set a truth table
Hope you enjoyed "