The Stovebolt Site Forums The Shop Area The Electrical Bay Am I In Over My Head?

I have a 1949 Chevrolet 3100 that has an older restoration. I have the engine running like a sewing machine. The next project is to tackle the wiring. The wiring is a mess. The truck has been converted to 12 volt. The turn signals don't work. The gas gauge doesn't work. The brake lights don't work. Looking under the dash is a wreck. Wires have come undone. I can't make head nor tails on what goes where. So, I think my best solution is to buy a new wiring harness and starting over. I've never tackled anything like this. Am I getting in way over my head? My biggest fear is that I will start and in the middle of it, find myself lost and not knowing what to do. I've ordered a wiring diagram manual for the truck. Can anyone give me any advice for tackling this project?

Wiring 101 is just about as intimidating as any project you can tackle. Stop, take a deep breath and study the wiring diagram to get an idea where to route everything. When you get your new harness device it into the three main parts. Run all the underhood wires through the firewall but don’t hook anything up. Then run all the tail light, brake light, turn signal and tag light wires along the floor board and out the back of the cab. Then bundle all the underdash wires up and out of the way. Start wherever you want and route/hookup all the wires in that area. Then move on to the next until there’s no wires left. You can do it. Others have done it and you’re just as good as they are.🛠

What non-standard electrical-equipment, besides turn signals, do you have on/in your truck?
Is it 6v or 12v?

How do you tackle under the dash with the dash all together? Do things need to be taken out of the dash to have room to work under there? I'm also not real sure about fuses and relays, etc. I would almost pay someone to do it for me if I knew someone good who was close and could do it.

Darrell,

What non-standard electrical-equipment, besides turn signals, do you have on/in your truck?
Is it 6v or 12v?

This information will make it easier to give you helpful/useful suggestions/opinions.

"I've ordered a wiring diagram manual for the truck."
What part number and company - is a catalog on-line?

It's 12 volt. There's really no non-standard electrical equipment that I can think of. I do want to add electric wiper motors and get rid of the vacuum motor. There's an under the dash air conditioner, but I don't think the compressor works. Right now the fan works on it and that's all.

I ordered the complete wiring harness from LMC Truck. Part number 36-3000.

The first thing to do is take the seat out. Then build a small plywood platform that extends the floorboard far enough to lie down comfortably and work under the dash without turning your back into a pretzel. It's a lot easier to do accurate work if you're not in pain.

Then try not to go to sleep!
Jerry

i am an electrical engineer, so i do not find wiring to be intimidating at all - i actually enjoy setting that right. In fact if you were nearby, i'd rewire your truck for you. A good harness will come with a diagram, color code, point-to-point routing chart, and circuit function description. Use some tape to label the wires. Grab a handful of colored highlighters and cross off each wire/circuit on the wiring diagram as you complete them. Rewiring my truck was one of the most enjoyable parts of my restoration.

i got my harness from this outfit: www.lectriclimited.com and i was very happy with it.

you'll be fine - have confidence and you will be proud of your results!

Darrell,

It looks like you ordered a standard harness.

"I've ordered a wiring diagram manual for the truck."
Did you order a wiring diagram manual, or did it coming with the harness?
Are you referring to instructions that came with the harness?

If you do not have a schematic wiring diagram, there is a diagram on this page that can be downloaded in two formats (PDF & JPG). It will not have installation advice, but it defines/shows the colors and purposes of each circuit/connection. That information probably also came with harness you bought.
http://chevy.oldcarmanualproject.com/electrical/wiring/index.htm

Each add-on circuit/component should probably have a fuse. If a fuse did not come with that component/add-on, you should read the instructions for that component to determine the fuse rating (and, buy an in-line fuse).

Follow Hotrod Lincoln's instructions on prepping the cab for inside work. A sheet of 1/2 inch plywood will be more than enough. Extend it a couple of feet outside the cab supported by a couple of concrete blocks. As Jerry said, try not to fall asleep once you get under there. As soon as you do your buddy will shock you awake and you will have a dent in your forehead that matches the curve of the bottom of the dashboard. Good luck, you got this!

I've been over my head for 26 years. The fact that my '48 runs so well is testimony to these great engines and the great advice from this forum!!

Darrell,

I too have a 1949 3100 1/2 ton pickup. When I did my wiring I found it much easier to remove the speedometer, cluster gauge, radio speaker grill etc. and work with these components removed. Pass the wires through the gauge holes. I then worked from the left to the right starting with the headlamp switch, next to the gauge cluster and then the speedometer, re-installing each component of the dash after you have completed all connections. I didn't secure everything tight until I was sure all connections were made including the ignition switch and any accessories added. (ie: cigar lighter, glove box light, radio, etc.) Hope this will be of some help.

Tim

One other thing you need is a factory assembly manual for your truck. The wiring diagram will show you what wire connects to what but it won't show you where it goes/how it is routed. The assembly manual will have pictures that you can follow to see where the wires were bundled/routed/hung from the factory. Those two documents together and you will be golden.

You will find that the 1947-1955st Factory Assembly manual is really 54/55st.
One major difference (maybe the only major difference) from 1949 is the fuse box (and horn wiring).

I ordered a wiring diagram manual for the truck and the wiring harness also came with a diagram that is color coded. I also bought a complete factory assembly manual. I'm hoping between these, I can figure it out. I think I will be relying mostly on the wiring diagram that came with the harness.

Thanks. Are there instructions on this forum somewhere that shows me how to take out the gauge clusters? I think it would definitely be easier to do it that way.

Thanks Larry. I do have the factory assembly manual. I think it will be helpful.

Darrell, I don't know what stage or condition the rest of the truck is in. My suggestion is for a truck needing refreshed/rebuilt/restored. What I do is similar to what some have said. The members above have put you on exactly the right path with great info I agree with 100%.

Do the harness AFTER you Take out and take off, all that stuff you said does not work. Actually take out/takeoff every electrical component. Lights, switches, motors, gauges, etc. Take each one to the bench with a 12V power supply. I use a battery charger. I have fun "rebuilding" each electrical component. Testing operation, sanding the contacts, soldering/crimping where needed, cleaning, shinning.........figuring out what is wrong with each and getting it working or replaced.
It's rewarding and very good experience.

You will find that most of the components are all the "same". I even take switches apart by bending the tabs that hold the phenolic back or plate, cleaning the contacts on rotary, toggle, push-pull or any sort of switch. Switches are elecrto-mechanical. I too was an engineer but these components are not difficult to understand, quite simple but well done. Motors are all the same, blower, starter, generator. Lights are all the same, socket shell, spring loaded contacts, bayonet bulb. You need to shine up all the copper and brass contacts/terminals and bits inside and outside the electrical components. Repair any broken mechanical or electrical parts they have. Test continuity and operate them, as said, with 12V supply. You may want to rig an inline fuse on the positive lead of the power supply, with a 5 amp fuse just to be safe during testing until you know what is wrong with the component. You can use a 12V battery if you wish if you don't have a charger.

All these components are grounded via a super long and multi piece return path back to the battery. Mostly accomplished by intimate metal contact and a few wires/braided/cables. A faulty ground path is usually the cause of electrical problems more than 50% of the time. So that is your other task before the harness install. Inspect, clean and be sure there are all the grounds. Battery to frame, frame to motor, frame to body. In any order you want. All those items are mounted with rubber so a flexible ground wire/cable/braid is necessary, Bolted to a super clean bare metal spot. Do all these things first. The harness install is pretty easy and will make a lot of sense if you just look at each wire on the schematic and see how it supplies fused/switched/unswitched power to each component. That's all most of these wire do.

Any more info on this pass will be boring, you will have questions as you go. We are happy to answer. After you do the above, the process in general is to mount the fuse panel and then route the input wires from the battery to the fuses (or direct to a component in a few places) and route the output wires from/thru the fuses to each switch or component or light or motor or gauge. Then there are some ignition and charging circuits. Not a lot of wires really. Not over your head. Don't throw away ANY old connectors, clamps, contacts, switches, terminals, braids or funky looking electrical bits.

Darrell, To remove the gauge clusters. First look, you'll find a U shaped metal piece holding each gauge in place. Remove that.

Well, I'm not sure I got the right wiring harness. The harness I ordered from LMC truck is a reproduction wiring harness for the 1947-1955 truck. Looking at the wiring diagram that came with the harness, it looks like it connects to a generator and voltage regulator. My truck has been converted to a 12 volt system with an alternator. I also don't see any wires in the wiring diagram for adding an electric wiper motor or wiring up to the radio or heater. It's mainly ignition switch, dash lights, directional lights, headlights, parking lights, stop lights, brake lights, dimmer switch, and headlight switch. It also goes to the ignition, fuel gauge, ammeter, horn, and fuel tank sender. I'm not at all sure I have the harness that I need. Not a good start to this project.

A "standard"/original wiring harness would not have wiring for radio, electric wiper, or heater (or, turn signals, or, dual rear lights).

What is the LMC part number?

Part number is 36-3000. Complete replacement wiring harness for 47-53 Chevrolet.

Yep, that is the standard/minimal truck harness.

No big deal. Just keep in mind that a hot wire from the battery positive supplies the fuse panel "hot bank" side of fuses. There are two ways this happens. One is a direct hot wire to a certain fuse panel hot bank that is not switched, I.E. you decide you want the brake lights, horn, radio to operate with ignition off. That's called "unswitched" power. The second way is a direct hot to the ignition switch and then, from the "on" terminal on that switch, a wire goes to a certain other fuse panel hot bank. That's called "switched" power. The ignition switch "turns on" the fuse panel. You can see that concept by studying the way the harness is presented and looking at the diagram and instructions. Use the gen/reg wires in another place. Cut them off and just use them as new wire somewhere as alternator wiring or for your non-original components. Don't cut those wires yet.

There could be other "non fused"/direct connect wires like to headlight switch or ammeter. Since my rule is everything should be fused, then these would need a fuse or a fusible link at their starting end. Google fusible link.

Google how to wire an alternator either 1,2, or 3 wire method, whatever you want. That is easy.

The wire leaving a fuse will generally go to a switch, almost everything has a switch. Then a wire out the other side of the switch goes to what ever the switch turns on. Like a wiper motor, a radio, heater motor, brake lights. The return path (battery negative) is metal case or housing or socket to metal. Hopefully you have enough extra fuse spots for those items that were not original equipment. If not, you can just use inline fuses. Wire up what you understand and what you see on the diagram first and then we can take up the rest here.
If I had the wiring diagram you got, I could be more sure of what I advise. But you get the gist. The horn and it's button are different than anything else. Later on that.

You don't have a major issue and the wiring will turn out OK. Just get busy so that you get more understanding as we go. You can't know all about wiring without starting to read and wire up what you understand. You can do all the rear light stuff, gauges, front lamps, ignition by following the instructions given. If they are good instructions. We are open 24/7/365.

Should I buy a fuse block for all of these things to go through? The truck has the old fuse block with the old glass style fuses and there are places only for the headlight high and low beam, tail light, stop light, and parking lights. I don't see a fuse block for anything else to run through. I think for some of the stuff, they ran inline fuses.

Part number 30001 - Painless 14 Circuit Universal ATO Fuse Block Assembly at Classic Industries looks like it would be a good replacement or add-on to wire up accessories such as the wiper motor, radio, heater, etc. that the basic wiring harness I have does not have leads to. The other option is part number 70114 - Painless 3 Circuit Cirkit Boss®™ from Classic Industries, which is a fuse box that lets you add 3 circuits to your existing fuse block.

Any suggestions here?

My fault. I assumed that it was a universal style harness with a prewired fuse box with extra circuits. If they sold you a harness that is just a bunch of colored wires with a few connectors, it's a huge rip off. They even tell you to BUY a wiring diagram. A "reproduction" harness, which sounds like a factory harness that spans 47-59. Really?
I understand why you bought it and thought it was what you needed.
Maybe this harness appeals to the purest person. But this is pure fake advertising to the unknowing. There is NOTHING reproduction about this harness.

You can see that places like Painless have huge description paragraphs and a complete parts list for each harness kit.

Darrell: I see you are thinking you need an add-on kit to make the LMC kit usable. I can't say what is best now. I can't figure out what the LMC has and doesn't have. Here is a kit that seems to have more for same price as a comparison.

bartamos : " I assumed that it was a harness with a prewired fuse box with extra circuits. If they sold you a harness that is just a bunch of colored wires with a few connectors, it's a huge rip off. They even tell you to BUY a wiring diagram. A "reproduction" harness, which sounds like a factory harness, that spans 47-59. Really?
I understand why you bought it and thought it was what you needed. It's not really.
Maybe this harness appeals to the purest person. But this is pure fake advertising to the unknowing. There is NOTHING reproduction about this harness."

36-3000: That harness is sold as matching 47-49 (except no cloth/braided covers - the only difference).
Reproduction: Complete wiring harnesses build to original dimensions (appealing because they have terminated to the correct lengths)

The color coding matches the original color codes.
It will work as advertised.
Non-original fuses will need to be added (no false advertising).
It is wired for the original multi-circuit fuse box (trimmed/cut to fit, presumably).
Some additional wiring for options have been added as noted in the listing.

It may not be true "reproduction", but it matches the original standard circuits.
If you want more, yes, you should buy more.

It's Garbage compared to what I linked. Many of these trucks came with NO fuses or 4 fuses. When they did it was a fuse holder under the hood in a bad environment. Color match is no big deal. You are not matching anything. They all have several colors. When you are rewiring, you follow a schematic or diagram.
Tim, I just don't agree with you this time. I stand by my opinion. I can't make a silk purse out of this overpriced harness. I ask you to compare what I linked, for the same price, and tell me that this LMC harness is OK to buy for any reason. It;s not reproduction without cloth. It's not anything but a bunch of wires as far as I can tell from no printed information and no meaningful description and no picture.

I am not arguing that there are not better harnesses for someone who wants to add circuits.

I am just pointing out that he got what the vendor advertised, and it would have quite well done what it is advertised to do: fast and easy wiring of original circuits, using the original fuse box.

The vendor described the harness clearly and correctly.
Jim Carter, Classic Parts, and Chevs of the 40s sell similar harnesses.

I don't like disagreeing with a buddy. Right now I don't know what I would do.

Darrell: If you are not frustrated with the discussion, can you explain in very specific terms exactly what you got with the kit. How many wires, what on their ends and any and all other parts, contacts, sockets, connectors, with quantities of each. A few good pics would be fantastic. Use the attachment manager. If you don't see fit to buy a whole new harness, maybe that info will help us recommend a plan and add-ons. That's all I can think of, I can't start suggestion before I know exactly what you have. I also would like to know what category you are in. Purest/original build, Upgrade build to modern, or other.

I purchased mine through rebel wire. Very easy! All wires state what they are every foot. (Ie break light). They were also easy to contact when I had questions. In fact they called back to ensure I was good to go. Just my experience and I highly recommend them.

FYI, the only experience I had before this caused many shocking experiences!

Chris

I finally had time to tackle this project today. I started by getting the wiring harnesses out and looking at the wiring diagram they sent me and trying to match up circuits. It only took me a little while to figure out how the wiring circuits run. One small set of wires goes from the ignition switch and ammeter to the coil and starter. Another harness is to the rear taillights and blinkers. Then there's a harness that hooks into the fusebox and goes to the alternator, headlights and parking lights. Pretty straight forward other than this wiring diagram references a generator and not an alternator. I'm not sure how I hook into the alternator. I've posted a picture of the fuse box, a box above the fuse box that has an ignition and field tab on it, and another box to the side that says deco remy.

The big harness hooks to the taillight connector and the fuel sending wire, the brake switch, and the dimmer switch and then moves on up to the fuse box. Then it moves in under the dash and connects to the headlight switch, the ammeter, the gas gauge, and the directional wires that go with the turn signal. It also has all of the gauge lights. I understand most of it with the exception of the alternator hookup. I also don't have a hookup for the heater, but the heater is already wired and connected to the old ignition, so I guess it's ok to leave it like it is. It was working before.

All in all, I think this harness will work. It is a direct replacement of the original except it doesn't have the cloth covered wires. I'll try to get some photos of the actual wiring harness tomorrow. I haven't started putting them on yet. I've just been prepping the truck by removing some wiring to get ready to install the new wiring.

"Truck has older restoration with 12V conversion", so not sure what's what for electrical. Looks like I see an alternator already wired? If so, just copy with new wire. Sounds like you are pretty much satisfied and will be installing harness soon. That's all good. Assume you checked the fuses for the components that don't work. Not sure if you need an add on harness at this point.

The black box is an Echlin VR32 external Voltage regulator. I assume because the alternator does not have internal.

Also, I believe the small gray can on left is a relay.

Left of relay may be an inline fuse?

It may help to mark and remove old harness in "one" piece. Then if there are any questions you can gently open it up by taking off sleeve/old tape and following wire. Mark all ends and describe to yourself where they were attached or make a drawing or take pix.

OK, I was able to do a little more work today. I worked on getting some of the old wiring out. Mainly worked behind the dash. Was able to get the gauge out that has the ammeter, gas gauge, etc. Having trouble finding out how to get the rubber grommet out without tearing it all to pieces. Anyone have any advice here? I figured out what the Delco Remy box is to the left of the fuse block. It's a horn relay. I need help in figuring out how to do the wiring with that in place because the factory harness has different instructions. The factory harness has two wires attaching to the bottom of the fuse block with the two connections that are not marked and then the wires go on down and hook in to the horn. On this truck, the horn is an oooga horn and it is mounted right in front of the fuse block on the fender well. The way it is currently wired, it is connected to the horn relay on the firewall. Also, on the alternator, there are two wires coming off the generator. The smaller lead (orange wire in the picture) connects to the field connector on the external voltage regulator. The larger wire goes inside the cab as part of the wiring harness and I have no idea what it goes to. On the top of the external voltage regulator, there is a wire connected to the ignition terminal that goes over to the coil. The wiring harness has two leads that hook to the alternator and then hook to the Gen and the F terminals on the voltage regulator. Mine does not have that, so I'm not sure how to wire this part. Any ideas? I've attached the wiring diagram and the external voltage regulator, horn relay, and a shot of the wires coming off of the alternator.

1. Don't know what grommet you are speaking of. Old grommets are torn out and replaced with new.
2. Alternator: See comments below.
3. Relay: No horn relay on orig. So it was added. See comments below.
4. VR see comments below.

The difficulty here is previous owner wiring, alternator with external VR with old ammeter and 12V conversion and some fuses but maybe not enough and older restoration and a new harness that does not know all that.

Did you read my suggestion about marking and removing old harness as "one piece" of history to fall back on ?????? Following a harness that has the motor running "like a sewing machine" is a good way to proceed. There is NOTHING better than a harness to copy (if needed) that is modified, non original, hybrid, and works. We can explain the workings of a horn relay and ammeter wiring and external regulated and how an Echlin VR32 and alternator is wired and so on. But it will take three weeks of posts. We can do it but take my advice: carefully mark, write down, draw pictures, take pictures and carefully remove all of the harness in as few sections as possible. You said you took some dash harness out, did you keep it in tact and hooked up until documented? I know you may not wire some things the same but some you will. I don't know how to stress this further. Each wire in the removed harness can be "buzzed out" (continuity checked) to identify it's ends. Without tearing it apart.

Also still recommended taking all items mentioned earlier to the bench to refurbish and test. Then you are ready to install the harness. No offence, but your questions are hard to follow. Just unfasten harness leaving all components, except dash components, where they are. Take harness out as one complete ugly, branched, bundle if wire and tape. Lay it out flat somewhere safe for now.
Where did you get the diagram you posted? It looks like American AutoWire?? Is it the one that came with your LMC harness? Are there more sheets?
"Factory Fit" is a trademark name of AAW. Looks like AAW 30905. The LMC page 112 says in bold caps. "Harness does not come with wiring diagram." ? If your harness looks like the diagram, pre terminated contacts, terminals and connectors and is from AAW, you are in fat city.

The Voltage Regulator and Alternator is wired as follows. A big wire from battery terminal on back of alternator goes to battery positive post. One of the two alternator terminals (side-by-side) goes to the field terminal on Voltage Regulator. Ign terminal on VR goes to the ignition switch "on" terminal. (switched power). Alternator case must have good ground. Supposedly the other side-by-side alternator terminal gets grounded. Yours does not seem to have that and relies on case ground. Bottom line is: you will probably be using the new harnesses "generator" wires and it's old style "voltage regulator" wires as new wires for your alternator and external VR. Just repurposed and rerouted somewhat.
P.S. If it was me, I would change to internally regulated alternator now. This gets rid of the VR you have, Wiring is way simpler. Probably more reliable system.

Relay: We don't know if your relay is for the horn or for the lights or fan or is even being used? Does not seem like an old ooga had a relay, and headlights take two, and 12V does not need, but you have to tell us where each wire goes. Basically a relay gets a hot wire on one terminal, a switched wire on another and an output to a component on the third. This is an example of an area to document to either duplicate or understand and upgrade

Positive power can come from other places than direct wire from battery. They can bounce off starter, ammeter, terminal blocks, fuse panels, ignition switch and relays. Just convenient places to tap into power. So be aware of that when you are examining how your truck was wired/will be rewired. Previous owners doing "restoration", rewire, 12V conversion, Alternator conversions.... are liable to do many things.

If you see questions, answer them, like we are answering yours. If you are way past all this BS above and have it wired, let me know so I can delete.

Where did you get the diagram you posted? It looks like American AutoWire?? Is it the one that came with your LMC harness? Are there more sheets?
"Factory Fit" is a trademark name of AAW. Looks like AAW 30905. The LMC page 112 says in bold caps. "Harness does not come with wiring diagram." ? If your harness looks like the diagram, pre terminated contacts, terminals and connectors and is from AAW, you are in fat city.

The wiring diagram came with the harness from LMC. It is AAW 30905 for 47-49 Chevrolet Pickup. That is the only sheet with the exception of a wire usage chart instruction sheet on the back. The wiring harness looks exactly like the diagram with all of the pre-terminated contacts, terminals and connectors.

My apologies to Tim. This is the "unknown harness", not identified, described too well or pictured by LMC. Possibly due to fair trade or distributor contract. At least, I did not see any indication or specifics on it. If it is an AAW, It is indeed, as Tim said, quality. AAW is the holy grail.
Even though is says in large caps, no diagram, it does have a good diagram. Like the other harness I have purchased from them.
Summit and Amazon do identify some harnesses as AAW. Maybe I missed it on LMC? or maybe they don't want someone to "go around" them?

Looks like an excellent diagram for rewiring your truck.
I fabricated my own harness after carefully removing the old and identifying all (or most) of the wires.
Good luck with your project, lots of great advice here

Are any of the components on the truck still 6V? Gauges, fuel tank sending unit, bulbs, etc. If they are you'll have to deal with that too. Hate to see some of them go poof if hooked up to a 12 volt supply.

Rick