Technical Painless Wiring Warning

Well, so far a couple of guys would get 'B' grades but no 'A's yet....

 

So much for Bell Curve.

 

have a kwik wire harness in my 40 Ford. been having elec problems when using a/c. an electrician friend put a meter on the single wire coming out of the alt. its a 10ga to the fuse block thru the harness then a 10ga down to the starter. he says they're too small. so I called kwik wire tech office. they said the 10ga to alt is not included in new harnesses any more & I should run a 4ga dedicated wire from alt to starter. just leave 10ga loose in harness wrapped in elec tape. just fyi

 

Good thing that I don't read instructions.

 

I have wired a lot of cars over the years, at first I made my own wiring, at that time I had very limited budget and needed very little to completely wire a car.

I have used just about every like out there, even a few odd ball kits but also used painless, Rebel, Ron Francis, but my go too is American Auto Wire, it is not a cheap kit but every thing that is needed in in the kit, including enough wire to do two cars.

I believe with the detailed color instructions broken down into different task my teenage granddaughter could wire a car with this kit with no problems.

I have wired & helped wire 7 cars with the American Auto Wire kits and have one sitting on the shelf waiting on my next project. HRP

 

To add some more to what everyone else said, if this the only wires to the fuse box then everything is hot all the time...no ignition feed.

 

Connections to the ignition switch are shown in a separate schematic.

 

The whole thing seems redundant to me since there's still source voltage if the alt is putting out. And if it can't go back to the battery then where are the amps going? Into the system and subject to whatever frailties exist in it. Whomever came up with this did feel good shit, nothing more.

 

Well, it looks like all who were going to reply did. Awful lots of hits; a bunch of nervous Painless users?

Before I unpack this mess, I will comment on why I think they did it this way. The aftermarket harness suppliers are notorious for trying to NOT use any wire sizes larger than #10. They'll try various gyrations trying to make the smaller wire do the work of a larger wire. That's the case here IMO. It appears here that in connecting one side of the panel directly to the alternator, they figured that shunting part of the alternator output to the panel would reduce the current in the 960 wire, allowing the use of the smaller #8 wire and smaller fuse. In theory it works, and as long as there's no other issues it'll be fine. The problem is if you do have any issues, this design creates more problems than it solves.

So, not necessarily in order...
1. I gave a 'clue' to tell how many wires that 50A maxifuse was fully protecting. The correct answer is NONE. The fuse does offer overload protection to the #8 ONLY, and may blow in a short-circuit but ONLY if the short is on the panel/alternator side of the fuse. The #8 between the voltage source (battery) and the fuse is unfused and if shorted to ground will sizzle until A. the wire burns away whatever it's shorting to, or B. the wire melts in half. One can hope that A or B happens before the wire catches fire, but with 500+ short-circuit amps available from the battery, time is probably against you.
2. Let's assume for a moment that the maxifuse blew under overload, just enough to trip it but not enough to melt any wire. If it trips while driving you may not even know it, and your first notice of it will be when you shut off the car and try to restart it. Or when driving, the alternator regulator fails and the car just quits. The fuse failing effectively disconnects the battery from the harness, and alternator regulators don't like not having the battery to reference to. This generally kills the regulator. I'll note that generators don't like this either, but being cruder non-electronic systems can tolerate it longer.
3. Going back to the short-circuit scenario on the panel/alternator side of the maxifuse, this is where bad things can happen. If the fuse blows, that at least removes the big fault current from the battery. But you still have unfused power from the alternator on all three wires. Depending on the output size of the alternator, you may or may not have a disaster. If you have a smaller alternator (70A or less would be my guess) it may fail before any major damage occurs. If it's a big 100A+ unit, you may have the A & B deal from 1 on your hands. Worse yet, if the short burns open the wire, that doubles the load on at least one of the remaining wires, putting that one at hazard and presenting another possible fire. Again, if you're lucky the alternator will fail first.
4. Last, the parallel panel feeders (wires 915, 916, and 960). This problem is the least likely, but not outside the realm of possibility. Wire has X amount of resistance per foot, with differences by AWG size. A shorter wire will have less resistance compared to a same-size longer one. Electricity will always take the path of least resistance. What this means as a practical matter is the shorter wire will be carrying more current. How much more is hard to say, that will depend on relative wire lengths, load and connection quality. If it's close, what will probably happen is the shorter wire will heat up slightly (increasing its resistance) until it reaches equilibrium with the longer wire. But sometime the rate of temperature rise is too fast so it shoots past the other wire, starting a circle that ends with one or both wires overheating, maybe to the point of damage/fire. Parallel feeders should always be the same gauge/length to prevent this.

The fuse they furnished is a 'magic token' more than anything else (Look! It's got a fuse so it's safe!). Very limited in operation and causes more issues than it cures. It would be much better to properly size/connect all wires and simply eliminate it. If you just have to have short-circuit protection, to make it actually meaningful you'll need to install a fuse at each end of those four wires because they're fed from both ends. Do you really want to deal with eight fuses?

Feel free to self-grade.... LOL

 

I suppose they could do it like Chevy did in the 80s, have several fusible links connected to the starter lug. Or like Ford did at the same time, they had several fusible links connected to the starter relay lug. I don't remember what Chrysler did. By the late 90s most carmakers had at least two fuse blocks in the car, with big fuses in the one under the hood.

we're getting pretty far away from the HAMB way of doing things, here...but I guess that's just the slippery slope you start rolling down when you put an electric fan in your car, which requires a larger alternator, which requires a #8 feed wire, which is more than the harness is made to handle....etc....

 

Crazy Steve; Now that we know the faults, what's your recommended fix for the Painless wiring harness? Upsize the gauge on a couple of wires as well as reroute a couple of runs? Easy mod on an uninstalled harness on the bench, but maybe a couple of heavy gauge 'home runs' for a harness in service on a Rod would be a relatively straight forward fix?
Can you "paint" in some fixes on your o/p schematic for a visual?

How do the other wiring harness company's compare in design and wire gauge? Rebel, etc. Ron Francis has been around 50 years...

 

Let’s face it. Traditional electrical systems were not ment for all of today’s fluff. If a company has to down size their wire like restaurants do there portions, then it’s up to us to bring the cheese to the burger. Meaning, Painless does not mean painless. Catchy company name but far from it.

 

When I re-wired my car I tossed the fuse block and used circuit breakers for everything. It is a simple car, lights, fuel pump, fan and ignition. ABC

 

What he said ^^^^^^^^ I have a Painless Harness waiting for installation in a 56 Chevy truck.

 

What I would do is run the 960 wire all the way to the starter solenoid, increasing the gauge of the wire as needed depending on the amperage of the alternator and the length of the wire. Eliminate wire 915. And increase the gauge of 916 to handle to max load that would be applied to it.

 

I'll throw my 2 cents in here since I just melted down my Painless wiring harness.

Let's start by you throwing the Painless 10102 under the bus but you're using an outdated schematic of the 10102 harness to do so, which I just bought last week, this is the correct schematic and they don't use the "maxi fuse" any longer.



With that being said my old instruction booklet of my previous equivalent Painless harness provided this as the only illustration.



And previous to that one it used a fuse-able link as in this illustration



Now back to my harness meltdown, I had the maxi fuse and it didn't trip, the wire from the alternator shorted and melted its way all the way back to the fuse panel.
Here's a link to my thread and photos

https://www.jalopyjournal.com/forum/threads/dont-do-as-i-did.1269925/

I would of expected a fuse to blow somewhere before doing all the damage it did, but it didn't and I was lucky to get the battery disconnected rather quickly.
Hopefully their new circuit breaker system works better.

 

This is exactly what I did on the last car I wired. It makes way more sense than the Painless diagram offered. I did install a Painless wiring kit a few years back and can't remember exactly what I did but I do remember thinking that the diagram sent with the kit (same as above) wasn't what I wanted to do.

Thanks Crazy Steve for taking the time to help others out. Wiring and pretty much anything electrical seems to be an area where a large number of car guys struggle. I see it often. Some want help and guys like you offering that help probably save some folks a lot of grief.

 

What the hell? I signed up for Carpentry not Automotive Electrics! Somebody screwed up my registration real bad....

 

The problem with all of those is they run the alternator output to the fuse panel. That wire needs to go to the battery, though running it to the starter solenoid works too. Then the maxi-fuse will actually do something.

 

That's what I thinking, but I still use the proper sized fusible link (because I like the way they look). I also like the idea of the Alt power on it's own dedicated circuit, but I would run the power for the internal reg (#995 in pic) off of the battery pole of the alt.

BTW this still has a "Maxi fuse" in the same spot as the old kit, it's just a different style of fuse.

 

And that's the answer right there. To determine the actual wire size, you should do a load calculation according to the loads you have.

Jim, that's not just a '80s thing. Detroit started doing this as soon as the industry made the conversion from 6 to 12 volts, maybe even before. In those days the OEMs usually built a 'standard' harness designed to take care of all standard equipment (lighting, ignition, wipers if electric) along with popular options like a radio, heater, lighter and clock. When additional larger electrical loads were added such as power windows, seat, convertible top and AC, each one of those loads used a separate, add-on 'sub harness' laid 'over' the basic harness. Instead of having just three connections at the solenoid battery post (battery cable, output from the charging system, a supply power to the main harness), you could have up to six or seven connections depending on the options installed. Overcurrent protection was usually handled by circuit breakers but sometimes fuses (no fusible links yet) and if ignition key switching was wanted, they used relays to switch them. The only connection to the 'basic' harness was a small control circuit to operate the relay coils. This was standard practice for years, and what you'd almost always find on a HAMB-era car. On the higher-end cars like the Caddys and Lincolns that ended up with most of this stuff as standard equipment, sometimes effort was made to integrate these circuits into the 'basic' harness but not always.

A brief history lesson here. Up though the early '60s, very few vehicles had unified fuse panels. Lighting fuses were generally found on the light switch, and fuses for things like the radio, heater, wiper motor and lighter were found at the point of connection to that device. In effect, most of the harness consisted of unfused wire. As long as everything was good, no problem. But then the harness would get hacked, the wire insulation would 'age out' and get brittle and fall off and the potential for a catastrophic wiring fire went up sharply. Detroit recognized this and switched to unified fuse panels starting in the early '60s. Fuses were now at the 'point of origin' of the circuit, much better protection. But you still had unfused wiring; ignitions, charging systems, and panel feeds were still unfused and they continued to use sub harnesses for some options. Again, as long as everything is good, this will be a reliable system and in terms of simplicity is my preferred method with a few improvements. Current new car harnesses are now much more integrated (and complicated!) because of the huge amount of electrical/electronics used on modern cars.

The aftermarket harness industry is pretty much still selling the '60s unified panel design, with all of its limitations. Again, not a bad thing but one place the industry does a disservice is they don't clearly explain just what those limits are. Most guys look at the kits, add up how many circuits they need (of all types) and buy one with that amount or more. But virtually every harness kit I've seen uses the same two #10 wires for the power leads to the panel, immediately limiting you to a 60A max connected load. If you're aware of one who doesn't do this, I'd like to know. Worse yet, it appears most of them aren't externally splittable, i.e. the switched half of the panel is supplied internally at the panel, you can't upgrade the feed to it. Again, if you're aware of one who doesn't do this, I'd like to know. This is a real shame, as that capability could eliminate those add-on harnesses and give you a truly unified fuse panel. For a further discussion/explanation of this, go here... Wiring 101 | Page 6 | The H.A.M.B. (jalopyjournal.com) posts 165 to 168.

 

"By the numbers", words to live by.

 

And I absolutely hate this chart. This isn't really an amps chart, it's a voltage drop chart. You can end up with way too much drop by using this. And mis-reading it can burn your car down.

 

How about a Kwik wire kit. How does that compare ? That's what I have in my 49 Buick. I was surprised at the small size of the wires going to the headlights, but I don't remember ever seeing a wiring diagram with it. But it's been a few years since I put it in, and the directions have disappeared. My kit was a 22 circuit I believe, and it had a 50 amp fuse from the starter to the fuse box.

 

I was surprised that the alternator wire was hot when it was disconnected from the alternator, I thought the power came out of the alternator into that wire.

 

It would be hot because it is still connected to the battery end
.
On Race-Cars where a battery isolator is required [that kills the engine] we run the charge wire to the Battery side of the isolator switch.[this prevents the charge looping and keeping the engine running]

But this creates another issue when shorting the Alt wire when working in the engine bay [a common race car occurrence]
So we add a decent sized diode to the charge wire, so it is "dead as a dodo" from the battery end.

Vishay make the diodes that are suitable.

 

Well, it does, but it also feeds back through the fuse box via the maxi fuse or the fusible link to the starter solenoid, that's the path the current takes to get from the alternator to the battery. So that circuit is always going to be hot if the feed wire from the maxi/midi-fuse is connected, or the alternator is running. Not a great design IMHO.

 

It does both at different times. It's more complex as to how the alt and reg work but electrical pressure flows to the lower number or point, battery voltage is higher then alternator output it flows to the alt, alt output voltage higher then the battery and it flows to the battery in a basic system.

 

what alternator output is required? 100 amp too much? 65 amp better? do know that a perfectly good looking alternator can have a diode failure that can fry the output wire to battery / starter, etc while just sitting still. - where fusible link comes in. what battery strength required? The information in this thread, and links to others in it, is terrific. but, average guy has a real challenge installing a pre-made kit. whether not that it is correct for vehicle set up they are working on or not. basic booklets, like one sold by Speedway Motors & Others "How To Wire Your Streetrod From Start To Finish" (don't let title scare you away) can help sometimes. try to print a copy of this thread & others in links, if that is OK?, to help do wiring right.

 

The page out of the manual for the 20105 harness ( 20105.pdf (painlessperformance.com) ) makes a lot more sense than the doodle.
It shows three power leads into the fuse block that aren't switched.

The "ignition switch" explaination page explains what each wire does.

For what ever reason I added the page for the hot all the time fuses and plugs and the switched fuses.
I'd think that the wiress going in from the battery/alternator have separate sections in the block.