Great tech thread, this is helpful for everyone. I will be doing my first cam change for my GMC 305 next month and will also post the pictures to. I like tech threads with pictures, hey it helps me all the time !
Installing the new headlamp switch is a fairly simple affair, but of course the crusty old one (it may be good, by why take any chances hooking all new wiring up to 54 year old switches?!) needs to come out first. With the instrument cluster removed, this is a pretty simple task. Start by reaching in and finding the release 'button' (more like a spring-loaded metal plunger) on top of the switch. You'll need to press down on this while pulling the headlight switch knob out. In my case, the plunger was corroded in place, and it took a little 'rap' with the end of a ratchet to push it down, but then the headlight knob and shaft slid right out. Then, use a large, flat-blade screwdriver to remove the chrome bezel-nut on the dash that holds the headlight switch in place. Now, the old switch can be removed, but don't discard it just yet! The new switch looks nearly identical to the stock one (camera batteries were dead during this phase of the operation, sorry!), except that the new one has a built-in fuse...and the terminal blades are NOT labeled, like they are on the stock one. Using the old switch as a guide makes hooking up the new one easy...just follow the labels on your stock switch and run your new wires to the appropriate 'blades' on the new switch using insulated flat-blade female connectors on your various wires. I ran a 10ga red wire from one of the fuses on the fuse panel up to the battery terminal on the new switch with a 15 amp fuse in the panel. This provides current to the switch. Next, run a 14ga wire from the headlamp blade ("H") on the switch down to the input on your dimmer switch. This will power up the dimmer switch when the headlight switch is pulled all the way out, and from there, the dimmer switch selects whether the current is being directed to the low beams or high beams. I removed the stock dimmer switch, which sticks up through the floor and has the wires routed under the toe-board, and replaced it with a new dimmer switch for a 69 Chevelle. The Chevelle switch is available cheap at any good parts store, and I mount it to the toe-board using two screws from the top side. This way, the wires stay inside the car. I mounted my new dimmer switch over the hole where the old one was and just had to drill two small holes for the sheetmetal screw that hold the new switch in place. There are three flat-blade prongs on the dimmer switch. The top one receives power from the headlight switch, while the other two get hooked to the wires which run to your headlamps. One is for high beams, one is for low beams. It doesn't matter which, the dimmer switch simply directs power to either one blade or the other. While making and connecting the wires to the dimmer switch, I include a second wire going into the terminal on the high beam side of the switch (the high beam side is determined by color wire you used in your Front Light Harness...in this case, red is for high beams, so I added the second wire to the red one). The purpose of the second wire is to carry power up to the high beam indicator lamp on your instrument panel. I like to have one hooked up so you know for sure if the high beams are on or not, but it's strictly optional. Then, I hooked the white wire to the other side of the dimmer switch, which is for the low beams. That simple! (There's still the ground wire under the dash that goes to the headlights, as well as the one for the brake and tail lights, but we'll get to those in a bit). Getting back to the headlight switch, the "T" terminal goes to your tail lights and the "Pk" terminal is for your parking lights up front. I have the power wire routed under the dash for the parking lights, but don't have good sockets for them yet as you may recall, so I left that wire unhooked from the switch for now. The headlight switch also has a provision for a ground wire, which I made up and left to be hooked up where all the other ground wires go. I will be hooking up my instrument panel lights later, so for now...the hadlight switch was wired. Installation is the reverse of removal...and that's all there is to that!
Wiring the brakelight switch is super easy, too. Run a 14ga power wire from a fused terminal on the Buss panel to one wire on the switch, the other wire hooks to the stoplight wire in your Rear Light Harness (in my case, it's an orange wire). I put a 5 amp fuse in for my brakelights and that was it!
Now, it's on to the ignition switch. This one has a few wires going to it, but taking them one at a time, it's an easy affair to get them all trimmed, fitted with connectors, and hooked up. First, the switch needs power, which once again comes in the form of a 10ga wire running from the fuse panel to the "Battery" terminal on the ignition switch. Next, you have "Ignition 1" and "Ignition 2". You'll recall that I ran a blue wire to the coil side of the ballast resistor, and a green wire to the input side of the resistor. "Ignition 1" is hot with the key in the "On" (or "run") position, and that's the green wire. "Ignition 2" is only hot while cranking the engine over, so the blue wire goes to that one (providing full voltage to the coil at start-up). There's a terminal on the ignition switch marked "Sol" (for Solenoid), and this is the red wire that leads down to the "S" terminal on the starter solenoid. Hook that to "Sol" and it'll crank the engine over when you turn the key to "Start". There's two "Acc" (accessory) prongs on the ignition switch, and I hooked the exciter wire from the alternator to one and the alternator light wire to the other for now. (Later on, one of the Acc terminals will power an accessory fuse panel...when I have accessories (radio, gauges, etc) to power!). The sockets on my stock instrument panel were in bad shape, so I opted to install an aftermarket indicator light next to the dash cluster. It's a small amber indicator lamp found at most truck stops, a simple two-wire 12v indicator lamp. Now, with the ignition switch wired and re-installed, and the stoplight and headlight switches wired and installed, you can bundle and secure your wires and put the instrument panel back in place. (I'll address the additional wiring for that later). See, it really isn't that intimidating when you approach it in some sort of systematic fashion, is it? Now you're ready to hook up the Auxillary Ground Wire and do a couple simple checks before trying it out!
For the Auxillary Ground Wire on this car, I ran a 10ga black wire from the bolt on the negative battery connector over to a bolt which I installed in a pre-existing hole next to the steering column. I used a 1/4-20 bolt about three inches in length and fastened the ground wire to it on the firewall side as shown, with a lockwasher and a nut inside the car. This leaves a couple inches of exposed bolt inside the car. I trimmed my ground wires for the various lights and headlight switch and fit them with ringlet terminals (putting two wires into each ringlet terminal). Then, I hooked the ground wires to the bolt and added another washer and nut. This effectively grounds my tail lights, stoplights, headlights and switch directly to the battery...insuring an excellent ground.
At this point, the car was wired enough to start, run and charge...and had working headlights, tail lights and brake lights, which is as far as I'm taking it for the moment. More things will be added later on, but this takes you through the various steps involved in wiring a car from scratch to where it has the very basics and can be driven, if everything checks out okay! Before you dive right in and blast off on a test drive, run a few precautionary tests first. With all switches off and all fuses installed, connect your 12v test light between the unhooked positive battery cable end and the positive battery post. The light should NOT come on, unless you have a dead short somewhere. If the light does come on, examine your work to see where the problem lies. I got no light, so I was ready to connect the battery cable and try everything out. I checked the tail lights first, pulling the head light switch out one click to see if they worked and they did. Then, I pulled the switch out one more time and checked the headlamps, which also worked. Trying the dimmer switch indicated that the high beams worked also. So far, so good! I turned the ignition to "on" and checked for voltage at the ballast resistor and my test light showed me that all was in order. Then, I bumped the key to "start" to see if the engine would crank over and it did. All that was left now was to start the engine and check the charging system! With the engine started and idling, I checked the voltage at the battery with my digital multi-meter and it read 14.8 volts just after start-up. Cool...it starts, runs and charges and the lights were working! Although the car still needs some work, I could resist driving it around some, so I cruised it all over town and drove it to work a few times before encountering any problems!
And, in the background, whispering as a sports commentator at a golf tournament does, I chime in "folks, this act, to assure a fault free ground might be the most important item that is routinely added to a basic wiring system, by a knowledgeable mechanic, in the whole wide world. FAt Hack knows his stuff and realizes that along the way, when troubleshooting malfunctions, however unlikely it might seem, on this car it is assured that a bad inherent ground will not be the cause of said malfunction. Now, let's return to the regularly scheduled program,........................"
I got home tonight and parked the car out front. Then, later I went to move it into the yard. It started right up and was idling fine. Being night time I tried out the head lights and they are WAY bright...no issues there. I put it in gear and it just died...shut right off! At first, I thought it was out of gas, so I dumped a gallon in it from a can in the garage, but that wasn't the problem. After a few tries, I realized that it would start while cranking then immediately die again. I walked to the garage and quickly fashioned a jumper wire for the ballast resistor and connected it across the wires on that useless device. The car fired up and I drove it into the yard. With the engine idling and the hood up, I pulled my jumper wire off the resistor and the car shut right off...confirming what I already knew! So, the lesson to be learned here is that if you have an ignition system that does NOT use full battery voltage...get one that does!! You can carry a box full of replacement resistors, or you can convert to HEI...take your pick! Unfortunately, it's not so easy on some engines. Nobody makes a drop-in HEI distributor for stovebolt engines. (Langdon's says they do, but if you've ever tried to deal with him you know you'd be better off asking Santa for one!). I'll try a Chrysler resistor for a points-equipped Slant Six for now, but I know it'll be a problem until an HEI is fitted to this engine...or the six is axed in favor of a V8...with an HEI ignition! But, the wiring job held it's mud and the car does what it's supposed to do, so I'm happy with that at least. I knew that resistor was going to be trouble, so it wasn't a total surprise. Luckily, it happened in front of the house so I didn't have far to drive with the jumper wire in place! If you wire your car yourself, then trouble-shooting it will just be that much easier! If you did it carefully and correctly, it'll almost ALWAYS be a component failure, and not the fault of your work. (Of course, I left my Engine Harness long enough so that a V8 swap will be simple and won't require any re-wiring work...and that useless resistor can be phased out easily and a full voltage wire can be made where it was and wrapped into the harness...just like that shit-ass resistor was never there!
Ha Ha, thanks Nash! The body grounds are still there...but I never like to rely on those alone! Doing it this way eliminates potential headaches later on from faulty or intermittent grounds. like you said!
He, he, he. On both my jalopys I run one like you did, then to the frame, then to the firewall to (coincedentally) a long quarter-twenty bolt for hooking up to in the future, and as a place to clip test meter to for any and all circitry searchs.
Nice tech, but I just wish it could be a little bit more thorough! This is definite must-read stuff for anybody doing a harness! Thank you fathack!
Exactly! My car still has all the factory ground cables and straps going to the firewall, body and engine...I just add that 'auxillary' wire for added insurance, and, like you say...to make future diagnosis and testing that much easier!
Stumbled upon your post doing some research for my 57 chevy truck. I did a complete rewire using an American Autowire kit. However after reading what you have posted, it does give me some things to think about. Thanks for all you hard work and documentation, keep it up.
WOW. A fantastic post. Talk about a day late and a dolla short. I just finished going through my og electrical system. I can't stress enough how useful just a thorough cleaning of these components can be. I really wanna look into getting sum of that No-Ox-Id compound to protect my work.
Know its an old thread, but just wondering how many hours total were spent on this. Need to do a rewire and just wondering what to expect. Also wondering why you chose connectors, I was thinking of doing everything with soldered connections?
The whole job was done over about a week's time working in the evenings. Maybe ten or twelve hours total working time. I used the crimp connectors because I'm comfortable with them and have had no problems with them in the past. If used and installed correctly, they do fine by me.
great post... i too just saw this for the first time. i'm getting closer to having to rewire my whole car too
Jim, im me when you're ready, I'll be done before you. I've got my engine bay wired (and am redoing a couple parts of it) and I'm about to do the lights/accessories in a week or two. I'm documenting it as I go. I'm doing it in very much the same way that the OP did it (coincidentally, this is my first read here too) - two 6 fuse panels. One's always hot, the other is ignition switched. I have a maxi fuse ahead of everything (it's already saved me once). Headlights & horn are on relays. I'm about to add a couple of buss strips to the mix too, which is why I've not posted anything on the matter yet- i'm sorting it out as I go.
I am needing to wire my 51 chevy and I am undecided if I am going to buy a harness or make one. Making one seems like a hell of alot of work and I dont have the knowlege
it IS a lot of work, but very satisfying if that's your sort bag. I'm about 1/3 done and I'm quite happy that I did it myself.
I keep reading and reading it. Did my postal jeep last year, and now im working on the econoline. awesome work and excelent explanation.
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