And that's why I hate 'full' wiring diagrams. Too much stuff crammed into too little area, and worse yet, there's always some critical information missing. They aren't useless though; that's where you'll find how the different circuits are interconnected, and usually get at least a rough idea of location. For detailed info, I look in the 'unit repair' section of whatever manual I'm using. That's where you'll find individual circuit diagrams, better yet you may find a more-detailed schematic. Unfortunately, not every manual has these or has them for all circuits. If not, you'll have to fall back onto the main diagram. That's known as a 'ladder diagram', and in terms of circuit clarity is the best choice, but can be very confusing in terms of component location. Truthfully, none of these should be considered the single 'best' way to draw these. When working as a professional, if it's a complex system I'd probably have all three types of drawings and would have to go back and forth between them to sort out just what goes where and how many wires go in between. And these diagrams really aren't drawn for the novice, they ***ume a certain level of knowledge in the person using them. If you lack that knowledge, they can be confusing as hell... And if you want a 'scale' drawing, better find a piece of paper about 3' x 8'. Any smaller and you'll start losing detail. Want to see a wiring diagram nightmare? About 25 years ago I bought a late-model family car. Fully equipped, computer-controlled, power everything. I decided having the wiring diagram for it would be a good idea if I had to troubleshoot anything, so I ordered it. What showed up? A 9 x 11.5 manila envelope 3/4" thick stuffed with 20+ sheets that unfolded measured about 2' x 3' each. I only looked at one; it had 'match lines' to another sheet on every side... Went straight to the recycle bin.... My recommendation if you're drawing something up for your own vehicle is to do multiple drawings. For component locations more-or-less to scale, use a 'block diagram' (this is the best description of what the OP first posted). Show the location of all major components including switches and relays as simple 'blocks' and label or otherwise identify them. Don't bother with circuit details, simply draw single lines between them to show what's connected to what. If routing circuits together, combine them into a single line to keep clarity in your drawing. You could ***ign numbers to each circuit and note those next to the lines. Then on other papers, draw each circuit separately, this is where you can show point of origin, fuse size, wire size, how many wires, switching details, etc. Ignition/starting can be one drawing, head/tail/dash another, turn signals another, etc, etc. You may think you don't need all this (and maybe you don't), but the next owner will love you...
And after you have drawn your circuits as above in Crazy Steves post, photocopy them, (a few sets), leave one in the car, one in the workshop, and hide one with your girlie mags. Also it's a bonus for the next owner.
No maybes about that first part. If you are looking at something to repair it then the schematic will tell you what ga and color the wire is/was/supposed to be as designed. Do you trust it??? Find a discrepancy or a mistake??? If you want to check or change something - you need to know about voltage drop, ampacity, and the load or amp draw. Making your own?? You need to know the same stuff - voltage drop, ampacity, and load or amp draw. Luckily there are charts that contain the info but you need to know where to find them, what to look at and how to interpret what is on the chart.
I'd love to post a picture of a circuit breaker. But due to limited access in the court house trust me when I say. "A home breaker panel won't fit under a dash board."
I like you Bob, I prefer a wire from the mag to a switch to two grounds, one on each head. Preferably a 60 amp switch.
If I am working on an OLD car and can't find a schematic for that particular car I find one that has all the same components of the car I am working on and go from there. You guys are light years ahead of me. Lippy
I am wiring a '46 ford. 351W, '60's alternator, regulator, point Dist., rear battery and starter solenoid. In stead of running another wire from the I terminal on the solenoid for the 12 volt source to the coil during cranking, can I just run a wire from the starter post? It will only be hot during cranking, right?
lots of good commentary in this thread. I drew up a simple diagram a while ago for a customer's car and ran it by the HAMB here. 'got a lot of good information and was able to clean it up and use it. the customer has had zero issues with it.
recently I modified the drawing a bit to better represent my current project I did not run it by the HAMB this time, hopefully I didn't miss anything critical (gauge sizes for this were same as above drawing)
'just noticed, I did run a wire from solenoid to coil byp***ing ballast resistor at start per typical even though it's not shown on either. and picked up volts for the volt meter from hot side of the fan switch.
And I thought I'd done something great today building a 4 wire extension so I could hook up the OT scanner to the OT computer in my OT daily driver pickup. I don't have a clue as to what the scanner is telling me but I felt really great until I saw @Paul's drawings. I'm going to go break out the 12 year old Glenfiddich and think about something else.
You also changed from an ampmeter to a volt meter. I was wondering about the 30 amp fuse in the charging circuit in the first drawing. Bones
The vehicle in question is a '28 AA Ford truck I've been working on since 2013(owned since 2000, but didn't start on it until I retired). I've gotton to the point of removing the body for prep/paint, so what better time to make the wiring easier to do. Brings me to this point of planning the electrical system prior to buying wire, relays, switchs, etc. I realy appreciate getting the expertise, the diagram, & the availability for Q/A if I hit a "snag"... THANK YOU HAMB!!! I've been "lurking" since about 2013, but for your question, I'm 76 ( & going on about 16 at times, just like the rest of you... LOL!)
@Paul should you add a relay on that fan? I have always been told that they draw too much amperage for a switch to handle.????
@vtwhead, You might be right. I will check into that. Sketch was based on manufacturers listed draw of 7 amps. It's a 14" straight blade low profile Spal. I ran 14 gauge wire with a 10 amp fuse.
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