Joined: Jun 15, 2014 Posts: 268 Location: Cambridge, Ontario, Canada
Posted: Thu Aug 07, 2014 3:47 pm Post subject: universal wiring harness?
Anyone use a universal wiring harness for their project? I have no wiring in my M38 except for a power wire to starter and turn key ignition. I will be going 12 volt on my project. I'm looking at this wiring harness I have linked below. I would like to try and use the existing light switch on the dash as well if possible. I have the old wiring harness so I have the plug for the rear of switch.
What has been your experience with universal wiring harnesses?
I'm still a long ways away from this step in my project but would like to get my head straight with how the electrical will go as I know having fuses and relays will be needed and I think a harness will help me.
If you know of any better/cheaper harnesses I would like your input as well.
Thanks
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Thu Aug 07, 2014 9:47 pm Post subject:
SP,
Just my two cents, but I believe you can use your original harness with allowances for the 12 volt conversion, and just have to figure out what you won't need. The light harness will be even easier, with the caveat on both below.
If all of your stuff is 12 volt and you are supplying 12 volts to the harness, then many of the wires and plugs will work. The problem you will have up front is you can't get 12 volt gauges and other switches with Douglas connectors on the back so will have to make a splice between the connector on the back and your old harness with the Douglas connector.
Not impossible, but will take some thought.
I bet at least ONE person on this board has done this. Hopefully you'll break all the eggs before I get there!
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Thu Aug 07, 2014 9:49 pm Post subject:
Key is you have the old original harness. That is a $700 big deal.
Wes has lots of stuff on his photo pages, including how to wire a standard 12 volt three prong headlight to a Douglas connector standard wiring harness.
B
Joined: Jun 15, 2014 Posts: 268 Location: Cambridge, Ontario, Canada
Posted: Fri Aug 08, 2014 4:08 am Post subject:
wesk wrote:
B you missed the first sentence in his post:
Quote:
I have no wiring in my M38 except for a power wire to starter and turn key ignition.
but I have original wiring harnesses Wes. But Bubba went and cut all the ends off. I have some of the plug ends. Someone was to lazyto actually remove the harness and just started cutting. Not sure if I have the ends for the headlights though. I will check on that.
Joined: Feb 20, 2007 Posts: 606 Location: Illinois
Posted: Fri Aug 08, 2014 7:41 am Post subject:
The original wiring harness on my M38 was crumbling away, with bubba installed jumpers running here and there. I thought I could patch my way to a working electrical system but that was not to be. I also wanted a M38 that had all the original blackout and running lights, 24v gauges and systems. So, I bought a repro electrical harness. Yes, they are expensive. But, in the end with the quick and easy installation, no fuss connections to military standard components and inclusion of turn signals - it was a good decision. _________________ 1951 M38
Southpaw, It really helps when you post the whole story first!
B must have been reading your mind or lives right next door to you!
If you have the whole original harness then repairing chopped off end is simple to get you back stock if the material in the harness is in good shape!!!!.
But, if you insist on running 12 volts then trying to create a Hermaphrodite 12/24 civvy/military harness/system is a lot more pain than it is worth. I have converted a half dozen M jeeps to 12 volt mixing civvy with military accessories and modifying the military harness to get there. It is a time consuming task for me and I am a professional Auto/aircraft maintainer/electrician.
Your best bet is to buy an aftermarket harness for a 60 CJ5 and make the few modifications needed to accommodate your accessories and switch selections.
It'snot a good idea to adapt the military light switch to a civvy 12 V lighting system but it can be done. Main issue is the amperage is higher in a 12 volt system then it is in a 24 V system thus the wire size is smaller and the circuit protection devices are rated lower in 24 V systems tan in 12 V systems. Only the very early Bendix light switches are without internal 24V rated circuit breakers. Rest of later switches have built in circuit breakers that will often nuisance trip in a 12 volt lighting system. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: May 30, 2014 Posts: 3447 Location: Texas Hill Country
Posted: Fri Aug 08, 2014 3:14 pm Post subject:
Wes,
I read where he had the original harness, but essentially no wiring in place.
I have nearly the same problem. The aftermarket toggle ignition switch has three wires to it, the oil pressure is tube to the gauge, the voltmeter has a wire to it, and there are a couple of wires to a toggle that turns on the headlights. Two wires to the battery. I can't even begin to describe what's going on at the rear.
Most wires are run through red rubber fuel or air line.
I figure I can start from scratch from the ignition switch and work my way west from there.
Looks like the wiring is a mix of 14 and 16 gauge. Does it make sense to use 14 for the 16 gauge wire, and 12 for the 14? The kicker then would be to replace the 25 amp breakers with something more robust. There appears to be a drop in 30 readily available.
You are right, dipping into the murky deep here with no paddle, but these things are not like trying to rewire a 1990's Caddy.
Besides, we have you and the other guys here to lean on!
To lean on us and be successful means to listen and pay attention.
Don't waste your time mix and matching. Go civvy or military. All the bull about I'll change it later is really bull. Decide today where you want to be with the jeep in five years and wire it accordingly.
Rarely are any original harnesses actually serviceable. The rare one that is will not be a Willys factory harness but a late 80's or early 90's replacement installed in the field.
You can have all the little GI thingies like BO driving light and BO marker and tail lights without going 24 volt.
With the military harness it is the little things that cost you dearly when you try to get by with a very old tired harness. Just try to picture in your mind the feeling you would get when the smoke starts rising and you are trying to remember which battery cable will disable the system instantly and stop the smoke!
When making a post where you are asking a question always insert the entire story. Don't assume that the entire membership has been watching your every post with bated breath and every member remembers the make and model jeep you own and your real name and what you did to it yesterday. Add your make and model jeep and your real name to your signature element so you don't have to remember to tell us who you are and what you are restoring. Notice that I keep referencing a real name. I find the almost silly CB type handles not very warming or personal. They are usually associated with the CB radio and the Facebook joke telling. When you come on here and ask for help with your project and expect a reply that will save you money, move your project along and keep you safe then it stands to reason that you should properly introduce yourself. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
Joined: Jun 15, 2014 Posts: 268 Location: Cambridge, Ontario, Canada
Posted: Sat Aug 09, 2014 5:21 am Post subject:
Thank you all for your input and advise on my project.
Since my M38 is all but a shell on a frame and rolling chassis and currently incorrect motor under the hood I will go with the civvy wiring. I had hoped to use the M38 light switch but did not realize amperage would be an issue. I will keep the dash looking original as possible and place the switches, etc in a less visual spot.
Wes, I totally agree your last post. People can't know everything about my project or my plans for what I hope it comes out like without me filling in the gaps. I will be sure to give more details in my future posts.
Thanks
Brad
Brad, I was in the exact same place as you and went through many of the same discussions in my head as you are now. In my case I had no wiring harness and no original M38 electrical parts left. Someone had replaced the M38 motor with an MB motor and converted the jeep to 6 volt. I agree completely with Wes in that you have to decide which way to go before your start buying parts.
After some careful thought and knowing my own capabilities I decided to go 12 volt. I also decided to reuse what few parts I had. I had the non original starter and generator rebuilt to 12 volt. I also purchased a CJ3A wiring harness from Walck's. They were great to work with and made some modifications to the harness at no additional charge. The harness was $255.00.
My jeep will never be an original M38. In addition to having no original 24V electrical parts, I also had no tub and the rest of the metal parts had so many holes drilled in them they looked like swiss cheese. In addition to limited electrical skills I have no welding or metal working skills so I purchased an entire reproduction body.
I'll be sticking with the non original motor also. In my case, the two realistic choices based on time, money, and my skill level was to part it out or go the route I am going. Any vehicle can be restored to original, but in my case the money that would have been required to return it to stock would have been far more than the value of finished jeep. I spent twice the current value restoring an old Corvette and I don't want to go that direction with my jeep.
Joined: Nov 01, 2011 Posts: 199 Location: Escondido, CA
Posted: Tue Aug 19, 2014 9:53 pm Post subject:
wesk wrote:
It's not a good idea to adapt the military light switch to a civvy 12 V lighting system but it can be done. Main issue is the amperage is higher in a 12 volt system then it is in a 24 V system thus the wire size is smaller and the circuit protection devices are rated lower in 24 V systems tan in 12 V systems. Only the very early Bendix light switches are without internal 24V rated circuit breakers. Rest of later switches have built in circuit breakers that will often nuisance trip in a 12 volt lighting system.
I've been thinking that one way to deal with this is to add a relay for the headlights, a la a modern vehicle, and use the original switch to control the relay coil instead of the full headlight current. The relay coil would be powered from where wire #16 is normally connected to the headlight switch (terminal M), with the other side of the coil grounded. The relay contacts would switch the current on wire that could come from the main light switch feed and go to the common terminal on the dimmer switch. The common automotive SPDT cube relay and socket are small enough to easily hide behind the dash (but still have access to from below). I haven't thought through it anymore than that, but seems like it would be too difficult.
Thoughts? _________________ Jim McKim
1952 M38 son-father project
Slowly turning rusty parts into OD parts
That would work quite well. I would power the relay trigger circuit with the light switch power and run a new circuit on 14 gauge wire to the main input/output of the relay and on to the two headlights via the dimmer switch. This 14 gauge circuit could originate at the starter + 12 V terminal with a fused link or circuit breaker close to that terminal. _________________ Wes K
45 MB, 51 M38, 54 M37, 66 M101A1, 60 CJ5, 76 DJ5D, 47Bantam T3-C & 5? M100
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