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DC Parts and strategies.

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Wiregeek

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There's a lot of folks that are adding stuff or fixing stuff that isn't great (looking at you tailgate glass lift motor grounds). I've seen more than one mention of ground lugs or fuse panels, and I wanted to get some info out. My day job is in two way radio - everything public safety from handhelds on fire fighters hips to dispatch consoles 911 call takers sit at. That includes cop cars. While our shop _can_ do a full cop car 'upfit', we try not to. But, I've done more than one, I've been trained, and I've got experience - and lots of experience doing maintenance and repair.

Here's what we use, for any aftermarket accessory setup from cop cars to ambulances, school buses to RVs.

Batteries
  • I don't care. Whatever junk the manufacturer provides. So long as it's the right chemistry for the charging system! Stick with AGM or SLA (Absorbed Glass Matt or Sealed Lead Acid). All things being equal, I'll reach for an AGM battery ( years ago, Optima. Today, Exide or Duracell - mostly because we have a local vendor that can warranty them).
  • Proper physical fitment. I've seen more batteries destroyed from mount failure than electrical abuse
  • Hose 'em down with terminal spray ( https://www.amazon.com/CRC-05046-Battery-Terminal-Protector/dp/B000CIPUNC ) just to give 'em a fighting chance.
  • Clean 'em with 120 - 180 grit sand paper or a wire brush. Your terminals don't need to be mirror polished, but they should be neat and tidy
  • Tighten till you can't remove by hand. If you can't, replace the cable end.
  • no direct feeds! Everything should have a cut off or disconnect near the battery, either circuit breaker or fused. ( https://www.amazon.com/Bussmann-CB285-40-Surface-Mount-Circuit-Breakers/dp/B01G5WHRPC/ ) an actual Bussman or other big brand, NOT chinese Yum Cha that costs a quarter of the real deal.

Power Distribution
  • From the battery we feed either a relay or contractor / solenoid ( basically a relay with current capacity in "whoah" numbers). That device is triggered by an 'ignition wire', a tap off of the stock wire harness that goes hot when the key is on. There's a million different ways to accomplish this, I like to use HVAC supply or similar. That makes our relay give us a "switched hot" output that only comes on when the key is on. OR, go straight from the battery to
  • A Fuse Panel / A Distribution Block / A Power Block. ( https://www.bluesea.com/products/5025/ST_Blade_Fuse_Block_-_6_Circuits_with_Negative_Bus_and_Cover ). BlueSea stuff is perfectly happy mounted to a panel underhood in a cop car in Barrow, Alaska, or a patrol SUV in Kodiak. Good solid product, available in 6 or 12 position, with or without ground, with or without cover. Strongly recommend the version with the ground and the cover. Anything so big it can't go on a BlueSea block (looking at you, winch) can go direct to the battery with whatever the manufacturer says for protection / disconnect.
  • Two fuse panels?!? Yep. Quite common that there will be two panels right next to each other, one labeled 'IGN' for a panel that follows the ignition switch, and one labeled 'BAT' that is straight (through a disconnect or big circuit breaker) to the battery.
Wiring
  • Proper sizing. There are a lot of 'ampacity' charts that tell you what size wire you need to safely feed any given load. A stock stereo may have 16 gauge wire and be just fine, where a 1000w amplifier wants chunky 8 gauge. There's no benefit to running 8 gauge directly to your HVAC fan, and it's gonna be a pain in the duck.
  • Proper material. I'm not 100% certain about CCA - Copper Clad Aluminum. But until proven otherwise, I won't let it anywhere near any of my vehicles. 100% pure copper for me, thanks.
  • Proper strand count. Most 'hook up wire' is medium strand count, 7 to 20. Perfectly serviceable and works for any number of applications. Solid Core (romex, THHN) is one solid chunk of copper - we don't gain anything by using that, and it's a lot more likely to crack or be damaged by flex or vibration. The alternative on the other side is high strand count wire, such as Arcticflex ( https://www.polarwire.com/ ). The higher strand count ends up being incredibly whippy and flexible compared to 'normal' wire, and the jacket is good from -67f to 221f. It's also much more resistant to flex or vibration damage.

Once you've got wire ran from place to place, you've got to hook it up to something. There's a whole field of engineering on splicing and bonding conductors - well beyond the scope of this post. But the short form is that the best 'normal' connection for an automotive terminal (ring terminal) or splice (butt splice) is going to be a heatshrinked crimp connection. It's not intuitive, but the crimped connection is the most vibration resistant form of connection. It's REALLY not intuitive, but over time it's also the better electrical connection!

But a poorly done crimp is butts, so spend the money on good tools ( https://www.homedepot.com/p/Klein-Tools-Ratcheting-Crimper-3005CR/306884697 ) and good terminals ( https://www.newark.com/c/connectors/crimp-terminals-solder-terminals-splices/ring-crimp-terminals ) by Amphenol or T & B. Throw some glue-bearing heatshrink on over the whole business ( https://www.amazon.com/Wirefy-275-Heat-Shrink-Tubing/dp/B084GWYX42/or similar - I don't have a 'good' brand for this), and move on.

My favorite is either pre-heatshrinked "Marine" crimps, or noninsulated versions that I then add heat shrink to.


Labels, mapping, flagging. The factory wire and wire diagrams have the benefit of using multiple colors. I can tell what the pink wire is when I find it under dash ( either Overdrive/ Kickdown or turn signal). However, if I run a mess of black grounds and red powers off a bluesea panel under dash or under hood..

I had the office buy a Brady BMP41 - and I think you should too. The secret is the self laminating vinyl labels. They wrap around the wire to label the wire, then wrap around themselves to protect the label. ( https://www.bradyid.com/labels/self-laminating ). Not cheap, but after a few WTF moments, it can be considered to have paid for itself. I have never regretted time spent labeling..

Please feel free to add anything or ask anything. WFH means I've got a fair bit of time between conference-calls-that-could-have-been-emails.
 
However, all this is good and well, but why should you care? Let's look at a real world example. I'm lazy, so we're gonna crib from @Blue85 's homework where he did the Relay Mod to his power windows.

Stock setup:
-Drop from Vbatt to switch = 1.5V
-Drop through switch = 1.5V (yes, the motor is only getting about 9V)
-Open/close time (engine off): 7.2s up, 6.2s down

With relays:
-Drop from Vbatt to relays = 0.3V
-Drop through relay and motor wire = 0.2V
-Open/close time (engine off): 4.2s up, 3.7s down

This is about a 41% improvement.
Click to expand...

In the stock original form, the "Drop from VBatt to Switch" is the difference in voltage when he measured at the battery (the best case scenario) and compared it to measuring across the switch. So his 13.8 volts at the battery is only 12.3 at the switch.

Which isn't bad. In this crazy "12 Volt" world, it's really almost always 9 to 16 volts that equipment has to be setup to work with - automotive electricity is a specially designed hell.

But that brings us to the second line. Another 1.5 volts dropped through the switch.

"Voltage" is just how excited the magic pixies are getting - It's PSI or KpA if you're more comfortable on the hydraulic or air side. We're ignoring amperage and watts right now, 'cause in the really real world Voltage is very frequently all you need. It isn't "how much power" is getting to something, but it pretty much works that way in the field.

So we're losing 3v through the crappy old tired wiring, crappy old tired connectors, and likely broken or damaged wires. We may also have intermittent loss of function. So our man @Blue85 runs a fresh power and ground to his door. Those wires feed relays ( wiring diagram https://ck5.com/forums/threads/power-window-idea-it-works.206618/page-3#post-2465482 there).

A relay is just a remote controlled switch. It's got four or five pins, and it makes a lot of sense when it's all laid out flat - it only gets confusing when there's 30 of them and none of them are labeled.

We'll ignore the 'advanced' N/O N/C pins, and just stick to a four wire relay. Two of your wires are "Coil", when one of those (doesn't matter which) is powered, and one (still doesn't matter which) is grounded, the relay goes clack and does the thing. MOST relays we're going to see follow a german automotive spec called DIN 72552 which nobody cares about and we won't mention again. BUT, it lets us here in the trenches at least have a chance of seeing "85" and "86" as the labels for our coil pins on any relay we find.

And lets us know to look at 30 and 87 as our "business end". When the relay is off, those two pins are not connected. When the coil is powered and grounded, the relay goes clack and those two pins are connected to each other. (inside the relay. Nothing should move on the outside).

The cool part and the why of the relay is that coils are tiny and cheap, electrically speaking. That crappy 9v that's all I have left after going through the switch is easily enough to make a coil do the thing. So now

  • I've brought a big 'ol new wire with good crimped connections into the door
  • I cut the original wire feeding the window motor and fed it into the relay coil.
  • The other side of the relay coil is grounded to the big 'ol new wire
  • My big 'ol new hot wire connects to the pin 30 on the relay (the 'input' - it actually goes both ways but whatevs)
  • the pin 87 on the relay (the 'output') is connected to the door motor where the original wire was.

I flip the switch and instead of a crappy 9v, which makes the motor go "nyeurrrrrrrrrbleeeeeegh" and crawl up against my tired old window seals in rusty track, the motor gets 11.5v ( this is experiment land where it's a perfect "12 volt" battery. In real life the voltage measured at your battery could be anywhere from mid 11 volts to mid 14 volts before it's time to fix stuff - though anything under 12 is usually a problem).

11.5 doesn't sound like a lot.. but think of it this way - we just made 2.5v of improvement in a system that is only 12v to begin with. that's over 20%, and @Blue85 's real world measured numbers make that pretty damn clear, since his windows are now 3 seconds faster.

And hell, MAW clean and lube all the hardware and replace any damaged or failed tracks while you're in there..


A side note on tailgates. The tailgate is perhaps the worst possible place to be a wire in the K5. frequent rotation of over 90 degrees? no sir, I don't like it. So it may be worth your while to get that fat new high strand power snake and a ground into that tailgate and do the relay mod there as well - I'm really looking forward to that one myself.
 
forgot to add where I stole the DIN spec and relay pin numbers - I had to look that stuff up, man!

Automotive Relay Guide | 12 Volt Planet

Read our guide to relays found in vehicle electrical systems. How they work, why they're used and some example applications
www.12voltplanet.co.uk

excellent guide there if you want a little more professionalism and a little less jaw jackin'
 
Nice write up!
Thanks for taking the time to simplify this. Wiring is generally more confusing for most folks than other aspects of a build.
 
I solved the slow tailgate window issue for good.
Click to expand...

Is there a word for when you admire the quality and worksmanship of something that you find utterly revolting? Man, that's good work in something that just.. turns my stomach.
 
Wiregeek said:
Is there a word for when you admire the quality and worksmanship of something that you find utterly revolting? Man, that's good work in something that just.. turns my stomach.
Click to expand...
I believe it's known as "keeping it to yourself."
 
Yeah, that's fair. I admire the hell out of the work though!
 
As much as I complain about coming in after someone has screwed up electrical, I do enjoy the challenge and the satisfaction of getting something straightened out.
 
There is a certain satisfaction in removing 150 feet of extra wire from a car/truck, and nothing fails to work worse that when the car came in 15 minutes ago. Then the fun of diagnosing why "they" did what "they" did. LOL
 
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