Inliners International Forums General Discussion Electrical Universal wiring harness

I recently purchased a universal 21 circuit wiring harness from the internet. I'm so confused, I could use a lot of help. My 50 Chevy wasn't wired with a fuse box and the original diagram is very different from the new diagram. For example...the headlight wires go directly to the headlight switch on the original diagram. My new fuse box has two wires, one is the headlight power, the other is the instrument light power. I assume the headlight wire now goes to the back of the headlight switch. The instrument wire also goes to the headlight switch, right? Can someone please explain this.
I can use a new diagram that will show me how to run wires from the fuse box to my stuff. Thank you.

Dear R-50;

This is to complex a project to be here because there are so many varibles etc.

Generaly; It's usually best to use the 'orginal' wiring as It's heaver than what's required for 12V operation.

Look for someone that's done this before, or get professional help/advice from someone that can look/see what you have there.

Good luck.

Buy a couple wiring books to help you out. I found it took me a while to get through them, but in the end I understood my wiring harness and electricity a LOT more. It also made it easier to track problems down.

I started with Randy Rundle's book. do a search here - he used to help out on some inliners projects.

royal50, I know how overwhelming this can be. My son and I used a simular kit to rewire his '54 Stude. John is right about wire size but in our case the stock wire was falling apart. It's also a good idea to have reference books and help. Has your car been converted to 12v? If not you have choices to make if you are going to try to use any 6v stuff.(heater,gauges,OD,some switches etc} Are you going to completely rewire the car or try to use some stock wires? Plan,plan,plan and remember you just do it one wire at a time. The more you look at it the more sense it will make.

I really appreciate all of you taking the time to answer me. I am replacing all of the old wiring. I put in a 70's inline 250 so it is a 12V system now. Someone did told me that I will have to get a reducer for my gas sending unit, and probably the heater.

What brand kit did you get? They should have an instruction sheet with their diagram. If nothing else, they should have a tech line.

In answer to your question, the headlights are normally one circuit and the instrument panel and tail lights are the other. They are wired this way so that if you blow a taillight fuse your dash lights will be out also and you should know to check your tail lights. The switch in most cases seperate the out going wires to tail lights and dash lights because the dash should have a dimmer. Your head light wire out goes from the switch to the high/low beam switch on the floor. then the out going power wires from there go one to low beams and one to high beams.
Hope this helps

Good,better to replace it all. I've never had good luck messing with fuel senders voltage needs but have used 12v senders with 6v gauges. I don't know why. It's more about resietance( ohms ) than volts, or luck. If you can find a real parts guy,an endangered species, with an illustrated blower motor catalog you can find a 12v replacement for your heater. On the Stude we use a 30 amp voltage reducer for heater and wipers. It's been working for 7 years. The last one I saw was in a JC Whitney catalog. Good grounds engine ,body,and frame and good connections are a must. Keep us posted. Oh.we did fry a light switch. Sude used a relay.

Thank you. I'll keep working on this.

Hi royal50 . . .

If you are using the original light switch there are separate terminals for the Head Lamps ("To Dimmer Switch" like big bill II points out) and for the Instrument Lights:
49-53 Chevy Service Manual - Chapter 12 Page 42

the index to the whole manual is:
49-53 Chevy Service Manual

A harness with a fuse panel is more complicated at first glance because everything has to go through the panel before going out to what is actually being powered.

Like Beater says spend some time studying before doing any wiring and you'll be ahead of the game. If you can find someone who has "been there done that" it would be helpful - but you learn more by taking your time and doing it yourself - or you learn just enough to ask some well thought out questions to the manufacturers tech line . . .

regards,
stock49

I'm not big on "universal" anything as they usually call for a bit more work on your part but if you study it a bit you shouldn't have any problems.

The headlight switch feeding from the fuse panel shouldn't be any problem to solve. The headlight wire from the fuse block runs from the fuse block to the Headlight "in" connection on the switch.
The wire from the taillight/dash light fuse will go to the connector that feeds the tail lights and the rheostat for the dash lights.
If you take it one circuit at a time you shouldn't have any problems. The main thing is don't make it harder than it is.

As far as the 50 year old "original" wiring harnesses go, I've fought them since they were 30 years old and most of them were already in poor shape then. I can only see using a reproduction wiring harness when you are trying to bring a truck or car up to a total "as original" restored status. That would be to satisfy the judges that you had restored the truck and not modified it with "new style" wire.

Oops I didn't look at Stock49's link that shows the original switch. If you are using an original switch you would just run the lead from the Headlight fuse to the connection that says ammeter.
You wouldn't use the taillight fuse for this switch.
If you have replaced the switch with a later style switch you would use the taillight fuse and lead.

Out of those 21 circuits you are probably only going to use about 6 to 8 on the truck.

figure Headlight
(taillight if applicable)
radio
heater
ac if it has ac
stoplight
Turn signal

The rest of the circuits will most likely be unused.

HI ROYAL --Good luck on the wiring -- You will get it in the end . When you do , consider installing some relays on things like headlights and NEW power accessories . It will keep the heat out of your switches and reduce the fire risk greatly . Hope this helps -- FLEET

Thank you to all of you. And you're right Mr48chev, I'm not using a lot of the circuits like power door locks, PW, AC, 3rd brake light, etc. Today I tried testing the lights and nothing happen. I ran the coil wire out of the fuse box to the coil, then I took the big red wire label as main power from the fuse box to the starter and pulled the headlight switch and no lights came on. What did I do wrong here?
Did I put the red wire to the wrong place?

What did you do wrong? You hooked up the battery before the harness was installed. I hope you removed the fuses from the circuits you weren't testing. You'd be better off using a multimeter for testing circuits without power on the truck/car until you have all circuits terminated.

I didn't remove any fuses. I guess I should of. But did I hook this up right? What do you mean by hooking up the harness. Can I just test the lights since they're all wired now?

What Cletis was referring to was that normally one hooks up all of the circuits he is going to use before attempting to put power to the system.
you can do what you want with the unused wiring but most guys eliminate it from the system. I think most of the time you can disconnect it at the fuse block. You get a cleaner look that way without a bundle of unused wiring tied up behind the dash.

Ok, which post on the starter did you hook the big red wire to? It has to hook to the one that has the battery cable running to it. Also the ground wires on the lights have to be hooked up.

You should have the the wire from the headlight fuse running to the (power in) connection on the headlight switch. the wire running from the headlight pole on the switch should go to the center pole on the dimmer switch and the high and low beam wiring should be connected to the respective sides of the dimmer switch. From there the wires run out to the headlights.

If the lights are not working I would suggest starting with your test light to make sure you are getting power to the switch and then out of the switch when you turn it on. From there make sure you are getting power in and out of the dimmer switch. (one side works at a time) then to the plugs on the lights themselves. It is probably easiest to start at the lights and backtrack through the circuit but going in either direction works ok.

Remember each circuit has to be a "complete circuit" to work. Power, switch, item that uses the power, ground.

Thank you, well explained. I could use this and check my system this weekend. I'll keep post.

Thank you, well explained. I could use this and check my system this weekend. I'll keep post.

Well, I got lights. I figured it out. I now have headlights, taillights, brake lights and parking lights. Now I need to do my turn signals.
Thanks again.

Got signals. Everything working fine.
I want to thank everyone once again.
Moving on to dash lights, then ignition wires.