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#1 2013-11-20 15:30:54

kornfeld
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Wiring up a car

I joined up with a new Lemons team recently, and we're in the process of rewiring the car.  It's a Volvo 240 with a Ford 302 in it, and when we got our hands on the car, it had a terrible rats nest of some Volvo wiring, some Ford wiring, and a bunch of spliced in garbage running to the kill switch/gauges/etc.  We figured out what we could, and then just tore all of that old shit out.  (It was bad.  Wires that were looped back on themselves; wires that ran from the dash, to the trunk, back to the engine compartment, and then weren't connected to anything; some grounds that also appeared to have power being sent to them; butt connectors that hadn't actually been crimped; you name it, we saw it.)



Anyhow, we have a new fuse panel which is really well laid out, and we're in the process of hooking everything back up. 

A question: we have a panel with some gauges and switches, and almost all of them require a 12V supply.  What would best practices be in regard to wiring those up?  The original car had one 16ish gauge wire coming in, with ~4,000 wires (poorly) soldered to it.  Most of those then went off to switches and gauges.  This is obviously a bad way to do things.  Should we run individual wires from the battery to each switch and gauge?  Or do we run one heavier gauge wire to a central point, and then branch off from that somehow? Any other recommendations for doing this? TIA.  embeer


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#2 2013-11-20 15:36:46

Bryan
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Re: Wiring up a car

Wouldn't you run a central to the panel, then off from there?


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#3 2013-11-20 15:47:43

kornfeld
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Re: Wiring up a car

Think about it like hooking up a boost gauge in one of our cars.  Many of us tap off of something like the clock wiring to power the gauge up. 

We basically have zero wires in the car right now.  So we can run a wire up there and then tap off of it, but seeing as we're starting from scratch, I was wondering if there would be a better, more reliable way to do it seeing as we have everything apart anyway.  embeer


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#4 2013-11-20 15:47:48

iamchris
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Re: Wiring up a car

802.11b

GET IT?!?  GET IT?!?  BAHAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

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#5 2013-11-20 15:48:49

bentmettle
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Re: Wiring up a car

Waytek's site isn't loading- BUT

You really only need the Ford bits to work, right?

I'd take a Ford diagram and just reproduce that with a terminal block, fuses, etc.

Some ideas for handling other bits in here, too->
http://www.painlessperformance.com/Manuals/10101.pdf

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#6 2013-11-20 15:55:17

kornfeld
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Re: Wiring up a car

I think the block we have is actually from painless performance (I didn't buy it).   biggrin


We've got the wiring diagram, and we can get the car running and all of the gauges and switches working.  We're just looking for any specific pointers on how we might do things specifically for a racing application that will be as reliable as possible.  Many times a manual will have you do something one way; when a slightly more complicated or labor-intensive method might yield rewards down the line.  Those are the things we're looking for now.  heart


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#7 2013-11-20 15:56:54

kornfeld
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Re: Wiring up a car

And yes, we're just focusing on the Ford bits for now, and we just need the motor to run, and the tach and tail lights to work.  We're gonna leave everything else in place (like for power windows, the dome light, etc.) for possible use in future themes.


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#8 2013-11-20 15:59:26

Bryan
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Re: Wiring up a car

About all I know about electricity is that a circuit with a lot of branches will have fluctuations on all the branches when one draws power.  Like how the lights dim when the a/c compressor kicks on, or how you trip a breaker in the house when a space heater and a humidifier are already running, and you turn on a hairdryer on the same circuit.

So it would make sense to me to isolate the starter, branch that off the main and have it fused independently of the panel, then run the main to the panel and run your distribution from there.  Since its a Lemons car, I assume you won't need a heater, a/c, interior lights (except the dash), horn, airbags, radio, cig lighter, etc., right?  Sounds like all you have to do is run lights, gauges, ECM/engine.


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#9 2013-11-20 16:00:15

Bryan
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Re: Wiring up a car

kornfeld wrote:

And yes, we're just focusing on the Ford bits for now, and we just need the motor to run, and the tach and tail lights to work.  We're gonna leave everything else in place (like for power windows, the dome light, etc.) for possible use in future themes.

I would strip the fuck out of it - you'll probably knock the weight down by a hundred pounds.


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#10 2013-11-20 16:01:48

bentmettle
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Re: Wiring up a car

cable clamp mounts for strain relief and a decent set of crimpers with AMP branch connectors are probably where dividends will happen.  As long as get the fuel pump, ignition, gauges, and accessories on their own circuits, that's probably pretty close.  How is that for a terrible answer? big_smile

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#11 2013-11-20 16:21:48

kornfeld
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Re: Wiring up a car

Bryan wrote:

kornfeld wrote:

And yes, we're just focusing on the Ford bits for now, and we just need the motor to run, and the tach and tail lights to work.  We're gonna leave everything else in place (like for power windows, the dome light, etc.) for possible use in future themes.

I would strip the fuck out of it - you'll probably knock the weight down by a hundred pounds.

It is stripped...all we're doing is leaving a few wires in place (that would go to power windows, dome lights etc.).


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#12 2013-11-20 16:24:11

davis
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From: Columbus, Ohio
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Re: Wiring up a car

As a long time lurker, I finally have some knowledge to contribute to the forum!  cool

On the three race cars I have wired I always ran a 14 gauge wire (probably overkill) from the battery to the fuse box. To distribute it to each terminal I sort of twisted in a bunch of short pieces of smaller gauge wires, soldered them to the end of the 14 gauge wire, and then connect those to the fuse terminals. We never had any issues with it and it appeased my teammates that were all about weight savings.

If you don't like that method you can always use a terminal block by the fuse panel.


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#13 2013-11-20 16:29:40

iamchris
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Re: Wiring up a car

arrow-up Welcome to the site!

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#14 2013-11-20 16:48:09

Aduck337
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From: Calgary, AB
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Re: Wiring up a car

iamchris wrote:

802.11b

GET IT?!?  GET IT?!?  BAHAHAHAHAHAHAHA!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

lol WIFI FTW


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#15 2013-11-20 19:06:26

kornfeld
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Re: Wiring up a car

davis wrote:

As a long time lurker, I finally have some knowledge to contribute to the forum!  cool

On the three race cars I have wired I always ran a 14 gauge wire (probably overkill) from the battery to the fuse box. To distribute it to each terminal I sort of twisted in a bunch of short pieces of smaller gauge wires, soldered them to the end of the 14 gauge wire, and then connect those to the fuse terminals. We never had any issues with it and it appeased my teammates that were all about weight savings.

If you don't like that method you can always use a terminal block by the fuse panel.

This is more or less what was in the car when we tore it out. We could do a better soldering job, but I'd rather go to crimped connectors or a terminal block like you suggested. 

There was one block already in the car that had all sorts of shitty grounding wires connected to it, and then one wire screwed to painted metal.  Pretty awesome.  star


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#16 2013-11-20 19:26:49

Bryan
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Re: Wiring up a car

kornfeld wrote:

davis wrote:

As a long time lurker, I finally have some knowledge to contribute to the forum!  cool

On the three race cars I have wired I always ran a 14 gauge wire (probably overkill) from the battery to the fuse box. To distribute it to each terminal I sort of twisted in a bunch of short pieces of smaller gauge wires, soldered them to the end of the 14 gauge wire, and then connect those to the fuse terminals. We never had any issues with it and it appeased my teammates that were all about weight savings.

If you don't like that method you can always use a terminal block by the fuse panel.

This is more or less what was in the car when we tore it out. We could do a better soldering job, but I'd rather go to crimped connectors or a terminal block like you suggested. 

There was one block already in the car that had all sorts of shitty grounding wires connected to it, and then one wire screwed to painted metal.  Pretty awesome.  star

Terminal block means that you can repair on the fly, without a soldering iron, too.  The simpler and neater it is, the better - sounds like some clusterfuck you pulled out of there.


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#17 2013-11-21 02:28:37

kornfeld
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Re: Wiring up a car

Here's another more specific question.  Should switches be wired on the ground side of a circuit, the power side of a circuit, or does it not matter? 

Why?


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#18 2013-11-21 08:01:47

bentmettle
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Re: Wiring up a car

Switch ground.  Usually will have shorter hot wires sitting there waiting to catch something on fire.  If your switch side wiring shorts out, it just turns whatever circuit on.  If the hot side shorts out, it will blow a fuse (hopefully) or worse.

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#19 2013-11-21 08:58:08

davis
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From: Columbus, Ohio
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Re: Wiring up a car

arrow-up +1


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#20 2013-11-21 14:12:19

tonka92x
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Re: Wiring up a car

I’ve wired a few vehicles in my time, even a few racecars.  Heck, you might have even seen some of my handy work, or it might just have woken you up in the early morning hours as it drove by.

My usual rules of thumb for wiring are: 
1.  Always use stranded wire.  NEVER use solid wire.
2.  Use a correct SAE J1128 wire, cross-link preferred.  I usually specify TXL.  In a pinch NEC MTW rated wire works.  Monsterwire, THHN, or the home improvement store "hook-up"  wire has no place in a mobile environment.
3.  The smallest wire gauge to use anywhere is SAE 0.8mm^2 / 18 gauge.  Smaller wire is not mechanically durable enough for a mobile environment unless properly supported along its ENTIRE length.
4.  Use properly rated connectors and terminations, properly applied with the correct tools.
5.  Proper wire protection (corrugated loom or expanded mesh) is required anywhere the wire is exposed to the environment or abrasion.  Or the user.

And did I mention that only stranded wire should be used.  Solid wire should never be used in mobile applications.

One issue I’ve seen over and over is using the wrong gauge wire.  Bigger isn’t better, and smaller can cause issues.  I usually will go with the smallest wire gauge that will do the job but no smaller than 18 ga for individual wires.  If I’m nearing the voltage drop I might go to the next larger wire but it depends on the likelihood of operating near that upper limit.  I use a custom spreadsheet to calculate this (I include connector voltage drops) but there are a couple of good sources for calculating wire voltage drop. 

http://www.gtsparkplugs.com/WireSizeCalc.html
http://www.rallylights.com/sensible-wiring

Remember, bigger wire is more expensive, heavier, more difficult to route, more difficult to properly terminate.  Use it when you need to, but only when you need to.

The usual connection schematic for the 12V side is:
Battery/Alternator -> Kill Switch -> fusible link  |-> large loads (starter)
                                                                     |->Ignition switch run relay -> fuse panel -> loads

If possible use a Flaming Rivers The Big Switch for the kill switch.  There is nothing better out there.

For the smaller load wiring I usually break things up as much as practical.  Usually 1 starter relay circuit, 1 ignition circuit, 1 cooling fan, 1 fuel pump, 2 gauge circuits (tach & secondary gauges on 1, oil pressure and secondaries on the other,)3 or more lighting circuits (each headlamp on its own fuse/relay, all other lighting on the other.)  Driver communications and any sensitive instrumentation (data acq) is usually on dedicated filtered power.

Terminals:  I prefer a sealed ring terminal for all screw-on style connections.  While not as convenient as a flag or hook style, they are much more reliable.  NS Krimp-a-Seal or Molex Perma-Seal are usual what we spec for any solderless connection.

If you need multi-pin connectors I have found none better than Deutsch DT (enhanced seal versions,) DTM, or DTP connectors with nickel-plated machined contacts.  The downside is you will need a $250 crimper to properly apply these contacts.  You could go to their AS series but you really don’t need them unless you are trying to make this more like an F1 or Indy car.  Amphenol AT/ATM connectors look good too but I have no first hand experience with them.  Delphi Metripack connectors are generally pretty good but have more assembly issues than the others and usually are not as reliable, but they are cheaper and available from many more sources.

Sources for all this good stuff:
http://www.waytekwire.com/
http://www.sherco-auto.com
http://www.mouser.com

High side (switched power) vs low side (switched ground) switching:  The answer is it depends on the load.  For something that must always be on or is safer when on, low side switching is preferred.  For something that is more likely to be off high side switching is preferred.  FWIW I always wire my systems as high side switching when possible.  Just my personal preference.

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#21 2013-11-21 14:21:41

bentmettle
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Re: Wiring up a car

I think my mind has just been blownedated.

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#22 2013-11-21 15:53:26

iamchris
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Re: Wiring up a car

Tonka, that may be a great post, but you keep using "proper" all over the place, and I have no clue what it means in each context.

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#23 2013-11-21 19:38:45

kornfeld
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Re: Wiring up a car

tonka92x wrote:

I’ve wired a few vehicles in my time, even a few racecars.  Heck, you might have even seen some of my handy work, or it might just have woken you up in the early morning hours as it drove by.

My usual rules of thumb for wiring are: 
1.  Always use stranded wire.  NEVER use solid wire.
2.  Use a correct SAE J1128 wire, cross-link preferred.  I usually specify TXL.  In a pinch NEC MTW rated wire works.  Monsterwire, THHN, or the home improvement store "hook-up"  wire has no place in a mobile environment.
3.  The smallest wire gauge to use anywhere is SAE 0.8mm^2 / 18 gauge.  Smaller wire is not mechanically durable enough for a mobile environment unless properly supported along its ENTIRE length.
4.  Use properly rated connectors and terminations, properly applied with the correct tools.
5.  Proper wire protection (corrugated loom or expanded mesh) is required anywhere the wire is exposed to the environment or abrasion.  Or the user.

And did I mention that only stranded wire should be used.  Solid wire should never be used in mobile applications.

One issue I’ve seen over and over is using the wrong gauge wire.  Bigger isn’t better, and smaller can cause issues.  I usually will go with the smallest wire gauge that will do the job but no smaller than 18 ga for individual wires.  If I’m nearing the voltage drop I might go to the next larger wire but it depends on the likelihood of operating near that upper limit.  I use a custom spreadsheet to calculate this (I include connector voltage drops) but there are a couple of good sources for calculating wire voltage drop. 

http://www.gtsparkplugs.com/WireSizeCalc.html
http://www.rallylights.com/sensible-wiring

Remember, bigger wire is more expensive, heavier, more difficult to route, more difficult to properly terminate.  Use it when you need to, but only when you need to.

The usual connection schematic for the 12V side is:
Battery/Alternator -> Kill Switch -> fusible link  |-> large loads (starter)
                                                                     |->Ignition switch run relay -> fuse panel -> loads

If possible use a Flaming Rivers The Big Switch for the kill switch.  There is nothing better out there.

For the smaller load wiring I usually break things up as much as practical.  Usually 1 starter relay circuit, 1 ignition circuit, 1 cooling fan, 1 fuel pump, 2 gauge circuits (tach & secondary gauges on 1, oil pressure and secondaries on the other,)3 or more lighting circuits (each headlamp on its own fuse/relay, all other lighting on the other.)  Driver communications and any sensitive instrumentation (data acq) is usually on dedicated filtered power.

Terminals:  I prefer a sealed ring terminal for all screw-on style connections.  While not as convenient as a flag or hook style, they are much more reliable.  NS Krimp-a-Seal or Molex Perma-Seal are usual what we spec for any solderless connection.

If you need multi-pin connectors I have found none better than Deutsch DT (enhanced seal versions,) DTM, or DTP connectors with nickel-plated machined contacts.  The downside is you will need a $250 crimper to properly apply these contacts.  You could go to their AS series but you really don’t need them unless you are trying to make this more like an F1 or Indy car.  Amphenol AT/ATM connectors look good too but I have no first hand experience with them.  Delphi Metripack connectors are generally pretty good but have more assembly issues than the others and usually are not as reliable, but they are cheaper and available from many more sources.

Sources for all this good stuff:
http://www.waytekwire.com/
http://www.sherco-auto.com
http://www.mouser.com

High side (switched power) vs low side (switched ground) switching:  The answer is it depends on the load.  For something that must always be on or is safer when on, low side switching is preferred.  For something that is more likely to be off high side switching is preferred.  FWIW I always wire my systems as high side switching when possible.  Just my personal preference.

Awesome.  I was hoping you'd chime in.  What are your thoughts about sending power to the switches and gauges?  Multiple wires all connected to the battery?  Or one wire up to the dash somewhere, then branches off to each thing?  If branches, what are your thoughts about using a terminal block?


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#24 2013-11-21 20:51:13

Scargo
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Registered: 2005-06-15
User Number: 227
Posts: 14179

Re: Wiring up a car

arrow-up if Tonka advises a bus (makes sense to me, for at least low load items like gauges and switches for firing relays) a terminal block is a very good idea vs. splicing, much easier to trace and repair.


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#25 2013-11-21 23:02:43

tonka92x
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Re: Wiring up a car

I have no problem “bussing"  common connections, in fact we do it all the time.  It is just the method of connecting all the connections together that is in question.

For power to low draw devices like gauges you should go thorough a fuse on your fuse block, then run an appropriate sized wire based on the voltage drop you are willing to accept (2-5% is common), then break the connections out to the various devices that need power relatively close to the device.  On production harnesses we sonically weld the wires together then jet seal (basically hot glue) the joint to weather seal the connections.  I have a connection in one harness that ties 32 wires together using this method.  This isn’t really practical in hand-built harnesses or even low volume production so we use other methods, in the following order of preference:

1.  Deutsch DT Bussed Receptacles.  These are basically a mating connector to a standard Deutsch DT connector that has all the pins bussed together.  To add a connection you simply crimp a socket onto the wire, insert it in the mating connector and you’re done.  Quick, simple, durable, but a bit pricey.  And these can be a pain to mount as they can get rather large quickly when you have a few of them.
2.  Delphi/VES Pack Splice Packs.  Same idea as the Deutsch DT bussed receptacle but uses the Delphi Metripack connectors.  Not as dense as the Deutsch solution (max 6 connections) but lower cost.  There are a bunch of parts needed to assembly these.
http://www.waytekwire.com/images/items/31990TH.gif
3.  Step-down butt splices.  Great if you have a single wire splitting into 2.  Lots of manufactures make them, Molex and National Standard are my favorites.  These do seal water tight if that is an issue, but you have to be careful to allow the adhesive to flow between the wires.
http://www.wago.us/images/Anreihbare-g.jpg
4.  Spring Terminal Terminal Block.  I’ll admit I stray from the ranch here – these are industrial parts but in protected locations in vehicles we have found them to be extremely reliable.  The terminal blocks can be bussed together via a small clip, it is very easy to add or remove terminals to be bussed.  Very vibration resistant, yet easy to add/remove wires.  These are a bit pricey once you get the whole system together.
5.  "Euro" style terminal strips.  These terminal strips have everything protected from shorting, but require a jumper wire to tie several terminals together.  Make sure you put this somewhere protected but accessible.  You need to check the screws fairly frequently to ensure they don’t vibrate loose and allow a wire to fall out.
6. Standard terminal strips.  Widely used but we find they have too much conductive area exposed, making them susceptible to shorting.  They are also susceptible to loosening due to vibration, but if ring terminals are used on the wires they won't fall off until the screw falls out.

Never use a wire nut.  They WILL vibrate loose. It isn’t a question of if but when.

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