1959 gmc wiring harness. What do I do?

[c Terris]

Hi, Because my truck is 57 years old and has had multiple owners, the wires in just about every place have been taken out and added to. New stereos have been put in and taken out. Im looking to get an oem and start from scratch. My problem is because Chevy's and Gmc's are different I could only find Chevy harness'. Where do I get an oem GMC harness. The harness in there now is worse under the dash which is where it is furthest apart from a chevy.
Thanks

[DransportGarage]

That's interesting...I wouldn't have thought the differences would have been that significant. Somebody here should be able to help you but it wouldn't be me.

[Softpatch]

Show truck .?
Only reason I could think you would want original 58-59 wiring.
The wiring that came in our trucks is not the best..
... One fuse on the back of the light switch Thats it.!
And a fusable link not much protection
Most of the taps are located either on
amp gauge or the Ignition switch.

If your not into scatch build there are some great aftermarket wiring kits
you could purchase
.

.

.

[Rickysnickers]

Wow, that looks like a fire waiting to happen.

[dsraven]

I am with softpatch on this one, show truck? numbers match restoration? if not, why not buy a kit or rewire it yourself from scratch? there isn't that many circuits and a stock harness wont be much better than you have there. access sucks but if you remove the speedo and glove box it gets better. get yourself a good pair of crimpers if doing it yourself and make sure to pull on every crimped connection to ensure it is gonna stay put. use double wall shrink tube on anything that will see weather or dampness, use some sort of loom to keep things tidy, or tape harness but that makes it harder to find any issues that may come up in the future. they make cable ties with holes for screws or you could use clamps.
you can do it if you just start with a fuse block and do a circuit at a time, soon you would be done.

[Daze57]

i agree with all the above --- get a new kit ---read the directions carefully -resort back to them as needed to be sure of your hook ups . take your time ----one circuit at a time as stated .its the safe way to do it + you;ll have 2 things - you did it yourself and you will know where everything is in case yo need a repair or an addition

just my 02 centavos worth

[dsraven]

if going that way, get a kit that will allow you a couple extra circuits for future use. if using a fuse box from a donor, same same.
-run relays for larger circuits like headlights, heater motor, electric fuel pump (if equipped), electric rad fan (if equipped) and horn (cause they tend to burn contacts).
-use a labeler to mark stuff like what relays are controlling
-make a wiring diagram as you go, then a nice copy of it all tidied up when you are done
-figure out draws on your circuits before you start so you don't overload
-figure out the capacity for different wire gage sizes so you use the correct size wire according to the load it will need to handle
-don't forget to run some good, large gage, ground wires from the battery to the frame and from the frame to the engine. also some ground wires from the battery to the body. whatever load goes out in the positive cables must also have the capacity to return in the ground cabling.
-bare the metal under the ground connections and use some star washers on the fasteners for the grounds. use some anticorrosion compound on the ground screws to help slow down the process.
-use some brush on electrical tape to slow down corrosion on these ground areas AFTER you have the wiring all completed.
-use double wall shrink tubing on any connection outside the cab at least. I use it on all connections but that is just me.
-have fun, go slow like a circuit at a time, you can do it.

[57chevyman]

I bought this kit from EZ Wiring for my truck. havent installed it yet...just on the fence between paying a pro to do it or not. This kit is one of the less expensive brands at around $200 with shipping.

[c Terris]

Thanks guys for the ideas, if i was to start anew and make my own harness what have people been doing as far as lighting up the gauge cluster? I assume most people have chevys and they just get a aftermarket one which wouldn't be a problem. For Gmc there is only one aftermarket cluster I could find and it doesn't look right. I rather have the original. For this there are little bulbs that go on the sides of the gauges and are grounded out on the cluster. They look different from lights i've seen before. Problably best just to use the one's in there now correct? I found the schematic for a 55 chevy it has done me well figuring out what was original and not. I have pulled all not original wiring. I have found the original wires match the schematic by the color and number. This truck has a 350 with a muncie 4spd. I may put the original to the truck 283 back in with the auto hydramatic. Time will tell what actually happens. The truck also has aftermarket heat and an msd ignition.

[Coupeguy2001]

As I remember it, when I rewired my 57 chevy truck,the harness came in 3 separate harnesses that plugged in together.
I got mine from a place in Arizona, and not sure what the name of it is, they were in Moreno Valley. ( I think)
every wire had a number on it, and it came with a diagram. Just match up the object with the number, and secure the wires.
It looked like to me that the underdash wires were separate, and the under hood wires were separate, and you plugged the two onto the main harness. Kind of like they made a main harness, and you plugged in the harness for your truck.
For instance if you had a V8 or 6, if you used an alternator or generator, or you had a 55-57 or 58-59.

When I put my overdrive and fan, and electric fuel pump, and stereo in, I made my own harnesses for those things and added a fuse holder for each system. I also went to auto zone and bought ten of those little 30 amp relays and wired them in for things like overdrive, fuel pump, stereo, 100 watt amp, cooling fan, etc.
There is plenty of room behind the seat if you use an under bed gas tank, kind of keep things away from under the hood, so it looks clean.

If you want to keep the in cab tank, try making an aluminum panel to mount your fuse block and relays to, and keep it high enough so you don't see it.
Buy a professional wire stripper and a professional crimper and color coded wire.
If you use relays, you can tie all the relay coils to the ignition switch and all the powers to a main battery cable that has a fuse holder block for each system.

You can make your own wire tags from those labelling machines, and it looks great. If you give them each a number, make your own list of accessories, and add the numbers to it.

You can even label each end of the wire.
For instance, 1 is battery to ammeter, and the ammeter end can be 2
3 can be ammeter to ignition switch, and 4 is the ign. end.
Or, 1 is battery to ammeter, 2 is ammeter to ign switch.
It really isn't that hard.
Say you want to add a cooling fan. the relay you want to use has a coil to actuate it, and a set of contacts to run the fan.
the ignition switch wire goes to the switch, and the switch wire goes to the coil positive fuse, and then out of the fuse ( .5 amp) to the coil positive contact. The coil negative goes to a ground point.
Then you have a lead from the battery to a fuse that runs the fan motor, say 10 amps, then to the fan. The fan negative goes to the chassis ground some where.

So what happens is that you are in traffic, and you want to turn on your fan. You flip the switch, turning on the relay coil, and the relay takes 12 volts on a red #12 wire to the fan, and a black #12 wire back to ground, and the fan runs.
If you want to incorporate the fan thermostat, it comes with the instructions on how to hook it up and where to place the sensor. To ensure long life for the thermostat, you use the thermostat to run another relay so it takes only a small amount of amperage to turn on the thermostat to run the fan.
simple and easy.
Just make a diagram, or list of the wire numbers, and have an area big enough for the relays. they are about 1 inch by 2 inches.
Most of them have push on contacts, so you get push on terminals and crimp them on the wires.
I like to use a 1/16" diameter rod where I want the wires to go, and use wire ties in a few places to keep the wires in check as I add wires, and make the bundle.
Then use a small screwdriver with the sides rounded off like the end of a spoon, and straighten the wires as you go, make=ing it neat and the wires straight.
if you start your bundle with a white, broun, red, and blue visible on the top of the bundle, you want to see those same wires on top through the entire run till they gt to where they are going, then terminate them with a service loop so you can change the part, relay, or wire if need be.
Wires need to be one size larger than necessary if run over 20 feet. Alternator to battery wire needs to be 6 or 8 gauge if over 36 inches.
relay cpoil wires can be 20 or 22 gauge, but the power wires need to be large enough for the items run.

[c Terris]

thanks, makes sense.

[HO455]

Having rewired several fifties Chevy's and a Ford, I can testify that looks pretty normal for a sixty year old vehicle. Your dash light sockets look stock for that era. They can be rebuilt. Yours look to be in good shape. (Not rusted around the area it clips on to the guage. You can clean up the outside and paint but leave the area inside the dash unpainted as it has to make electrical contact. Make sure the spring is good and the phenolic insulator isn't broken). They aren't to find used as so many people change their dash to something newer. You can buy replacement wire and contact assembly's or you can get the contacts separately and use your own wire. I believe last time I got the contacts was from American Auto Wire, but it has been quite awhile ago as I scored a box of them at a local swap meet. I have a 51 GMC that we drive lots and we used a repop wiring harness. It was so inexpensive that it wasn't worth the trouble for me to make a harness. It came set up for 12 volts with alternator and turn signals. Now this truck stock down to the 235 six and the radio delete plate. Not a lot of electrical needs. I did upgrade the wipers to electric as this is northwest Oregon and the guy who invented vacuum wipers must have been from death valley.

[4544speed]

One of the best investments I ever made was to buy a book from Speedway Motors called How To Wire Your Street Rod . It is not brand or year specific. It gives a good explanation for many wiring issues and conversions. It was only about 8 bucks. If you are not familiar with wiring, I think it is a good investment.

[c Terris]

Originally Posted by 4544speed

One of the best investments I ever made was to buy a book from Speedway Motors called How To Wire Your Street Rod . It is not brand or year specific. It gives a good explanation for many wiring issues and conversions. It was only about 8 bucks. If you are not familiar with wiring, I think it is a good investment.

Sounds good thanks
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[hogfarm]

Have you tried Ron Francis wiring?

[c Terris]

Just looked it up. Its the same thing as the others chevy not Gmc. These guys are the only ones that say gmc but I dont know why its say #2 harness. Their #3 harness isnt Gmc friendly and I dont see #1 harness on that page.

http://www.oldchevytrucks.com/cart/product.asp?prodid=EL172&i=9811%7C%7C%7C%7C%7C
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[c Terris]

I'de rather buys a harness pre made that I just have to clip in than buy a $500-700 kit to make my own.
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[ChuckDriver]

I had a panel from "Affordable Steetrods" in a car a few years back, nice and easy to install and worked great.

http://www.affordablestreetrods.com/...=cat/cat76.htm

[Russell Ashley]

You can buy an EZ-Wire harness for less than $200 that will have the fuses and wiring for pretty much every option that you might want in the future. I understand your wanting to buy a pre made harness but it seems that you have hit a dead end in that regard so I'm thinking that the EZ-Wire setup is probably the next best thing. You mentioned making your own so if you are skilled enough to do that installing the EZ kit would not be difficult for you, and probably about as cheap.

[hogfarm]

I sugeted Ron Francis because I am working with them now.My friend has a 67 Ford truck that we put on 2006 Crown Vic frame,they sell a kit to do the wiring,but they custom made it for the way we needed it.If you called them I'm sure they can custom design 1 for you as well

[Jemezcrusher]

What is the big difference between GMC and Chevy? The gauge cluster wiring. Can't imagine they can be that much different