Electronics Basics and Reference

the only thing that's confusing, are the LED lights on my truck...........

 

I totally forgot, your 2010 has stock LED tail lights. In that case, the trailer having LEDs should have no effect. I would have to assume that the blinker relay in your truck is the type necessary to run LEDs, so LED trailer lights should be fine. Furthermore, if the trailer lights are bulbs, you should be ok too because the solid-state blinker relay should be able to handle both LEDs and bulbs. I'd also have to assume the wire gauge running the tail lights hasn't changed from when they were running bulbs (like in my truck), so you shouldn't have any problem carrying the added current for trailer bulbs. Check your owner's manual though, it should say.

Let me know how it goes...this is just my best guess, I'm curious if it works out ok.

 

got caught up with other things this weekend, thanks for the info.
but i wondering if anyone actually knew the color combo of the cables i'm supposed to splice/tap into ?

 

or maybe if anyone had a wiring diagram for a 2010 taco ?

 

The only thing I have to add is in the soldering tutorial you should mention that a good solder joint is shiny on the surface. A bad solder joint has a dull color to it.

 

Diagrams are available in a Haynes manual, but also check out for the toyota manuals.

 

Another point that I remembered from a different thread:

Keep in mind the Tacoma uses negative switching. Under no circumstances are you ever to fuse the negative wires if you add a circuit. Doing that would be the mistake to end all mistakes. A short of such a circuit would start a fire because your fused negative circuit would mean the positive is unfused in a forest of unfused negatives that already exist on the truck. That would be a battery terminal to terminal short and it will surely start a fire in short order.

 

wow, very nice write up. subbed so I can study this when I have time.

you may be getting some pm's in the future from me

 

1000000% agree....power is coming from the battery...fuses should always be placed nearest the battery regardless of the switching logic.

Feel free...I'll help when I can.

 

The Noob guide to negative switching and why it's so easy to make a mistake:

If you decided to take power say under the dash instead of say the fuse box with a add a circuit. If you metered across a switch it would appear on the meter to actually have power if the switch was in the off position. One side of the switch on the Tacoma is actually just connected to ground. There is no positive at that point. Don't try to take power from existing switches. On the dash light part of the switch at that point you are actually in the middle of the circuit and not one of it's ends. One wire goes off to the dimmer and the other wire goes off so some other controller. You can't grab power there also. Only power for another indicator light. So unless you are connecting up another indicator light don't bother with that side either.

 

A good example of this is my running board/ground lights. I tapped the dome light for power and fused it, but I also had to tap the ground "signal" wire because it is the switch, not the power wire. Similarly, I'll be installing a SPDT switch...one switch turns them on, the other is connected to the door/dome light. To do this, the switch is on the ground side...the middle lug is connected to the ground wire of the lights while the first lug will be connected to ground an the other will be connected to the dome light control wire. I might add a note about this in my original post.

Note: I'd have to look at the wiring diagrams, but I don't think all of them are negative switched. For example, when I installed my fog lights, I tapped the parking light positive wire as the control power for the fog light relay.

 

There is a few mods around here taking power from a existing device which actually is just fine. For control power that is. Just that if you have been reading the forum on wiring gone bad. People asking for help cause they totally goofed everything right up they're making these basic mistakes. Since this is a Reference we also want to explain these mistakes so as simple as they are to make that they can be avoided at all costs.

It's deceivingly simple to make them unless you actually looked at the truck prints first. There may be some switches that this is not the case but most are. It's makes sense too because a fault will make a device turn on and refuse to turn off alerting there owner of a problem with the wiring. So you have two fault conditions, a burned out fuse or something that refuses to turn off.

Like how many people have stole power from the cigarette lighter cause they could not figure it out ? Not the best spot to grab the power from.

The simple logic of why you want to duplicate what the truck has if you add new switches. Picture this, basically the truck switches one side goes to ground the other side goes to the load then the fuse to the positive battery. So you want to add a switch but you don't know this is the case. So you run a fused wire from the positive terminal all the way into the cab to the switch back to the load then to ground. See the problem? There is no positive wires on the switches. You have introduced one in a confined space where there was none. Think about some future tech that don't know that you have goofed that up. If you keep it the same way the truck is wired already trouble shooting will be simple. If you do a good wiring job even the techs will not know they didn't do it in the first place. Again if you steal power from cigarette lighter that again is a positive wire. Not what the truck has. Not a good spot to steal power from also. It's a dedicated circuit. People have stole power from there then had problems with there sound systems.

 

Updates: Switch derating info added to switch section. In response to Trap's comments, a section on negative activated circuits (i.e. ground switching) added.

 

Like how many people have stole power from the cigarette lighter cause they could not figure it out ? Not the best spot to grab the power from.

The simple logic of why you want to duplicate what the truck has if you add new switches. Picture this, basically the truck switches one side goes to ground the other side goes to the load then the fuse to the positive battery. So you want to add a switch but you don't know this is the case. So you run a fused wire from the positive terminal all the way into the cab to the switch back to the load then to ground. See the problem? There is no positive wires on the switches. You have introduced one in a confined space where there was none. Think about some future tech that don't know that you have goofed that up. If you keep it the same way the truck is wired already trouble shooting will be simple. If you do a good wiring job even the techs will not know they didn't do it in the first place. Again if you steal power from cigarette lighter that again is a positive wire. Not what the truck has. Not a good spot to steal power from also. It's a dedicated circuit. People have stole power from there then had problems with there sound systems.[/quote]


This doesn't make sense. What do you mean there is no positive wire on the switches. If you connect the switch to a positive terminal you have a positive connection. You state that if you steal power from a cigarette lighter it is a positive connection, then you say that is not what the truck has. This doesn't make sense also.

 

I didn't 100% follow what Trap was explaining, but I think he's talking about negative activated circuits.

Trap: can you provide a diagram to explain better your fusing/tapping concerns? I agree that you should always fuse the positive side, not the negative, but I'm not sure I follow your concern. Also, tapping a switched positive (i.e. the cig lighter) is ok as long as it is fused and grounded properly, even if that ground is via a switched ground.

 

Diagram will take time. Expect it later today. You can connect it anyway you want. But doing so adds more potential faults if one should occur in the future. If you just duplicate what the truck has there really is no power other than negative at the switches. If you bring in a positive there now you have power that could potentially goof things right up on a fault. (Think cross shorting across different circuits ) Wiring should be fine and really should never goof up but it does occasionally. Nothing is done for nothing so you have to ask the simple question of why is the truck wired the way it is right now ? When a fault occurs it's obvious and probably the reason why it is the way it is. A easier way of looking at it. The long wires running around the truck are negatives. The short wires are positives with a fuse on one end. If a frame short happened somewhere some thing will turn on cause it's now connected to the negative frame. No damage done and the owner will know there is a short cause only the key will turn off that thing that will not turn off.

If you do the the other way the positives become the long runs and the grounds become the short runs. If a short happens then to frame well the fuse will burn out and and it actually could take months for the owner to notice something is not working correctly.

Why stealing power from the cig lighter is a bad idea? It's a heating load and is rated at 100% already so that 100% says there is no spare power there. It's also a plug designed to supply 100% of the rated load to what ever is plugged in there. Products built to take advantage of that plug might be built with such a high demand. You don't run a lighting or motor load off a heating load in a house and you should avoid it here for the same reasons. Plus it's really hard to get to and it's fused sort of heavy. The existing switches are really only control wiring. There is really no current flowing threw them.( just milli amps ) They use relays for the high current part of the circuit. That makes the switches last and removes high current circuits from under the dash.

It's your truck and you can actually wire it up any way you want. You'll discover I don't really give a damn. Don't complain though if and when you accidentally short something out then discover that short actually run high current threw the dash in series on existing original circuits burning everything out like somebody already did.

The biggest danger here though is a simple one. If somebody was to use a meter trying to find a positive at the switches it will appear to be positive if the switch is in the off position. That's the danger. Hooking it up to that seemingly positive wire is actually hooking up your new circuit in series with a existing circuit. Series is bad news. If your new circuit is high current nothing good is going to come with this setup when you turn that switch off. Well if you have marshmallows maybe some good.

 

Thanks for the note. I think I sufficiently addressed the overall issue in the negative switching section of the original post. It comes down to getting a wiring diagram and getting it right. Care must always be taken when tapping stock wires...if I do, I only do it for LEDs or a relay control line.

 

You have seen motor starter control ladder diagrams right? Notice the hot wire does all the work. You might use 50 meters of hot wire wiring up the box and a meter of neutral wire finishing the job. The truck is the exactly same way. The negative terminal is the hot wire and not the positive wire. The negative wire does all the work. Basically they have fused the positive (neutral) wire on the truck but that fine it's DC. Who cares as long as it works. The thing is the truck is also negative ground so it makes sense to keep the positives as short as possible, and the fuses as close to the battery as possible. You keep the fault path very short. The fault current potential in a short could easily be over 1000 amps. You don't have that kind of current available in a house on a fault. Makes sense to keep those runs as few and as short as possible.

That is the way you have to do it. Everything there is already being consumed. You can safely add a few milliamps to a existing circuit no problem without loading up existing circuits more then they should be. If you need more add a relay and a new fused circuit. What is there is just good enough for control unless it's a spare circuit.

 

Don't know if it's any better to make a diagram or not. Um I looked over what you have, makes perfect sense to me. Things to keep in mind if you meter across a switch and the switch is off you will measure the system voltage. 12 volts here in this case. The clue comes when you turn that switch on. The meter will now show 0 ( zero ) volts. There is no power there. If you measure from the switch to ground and it's open one wire will show 12 volts and the other 0 volts. If you turn it on both sides of the switch will show zero volts to ground. If you hook up things here thinking it's a positive your new circuit will actually be in series with the original circuit.

Things you want to do is keep positives as short as possible so there is very little length of wire for a fault to occur on. If you develop a short on a negative wire running all over the truck who cares the worse that can happen is something will not be able to turn off.

The prints of the truck actually show it's wired like as in everything is positive and little tiny lines going to the grounds but when you think of it most of the positive wires are located in the fuse boxes and it's actually the negative wires that have length to them. There is very few areas where positive faults can happen. There are also two fuse boxes. That keeps the number of positive wires down even more. If you yanked the entire wiring harness out of the truck and took it apart you'd discover over 90 % of the wire is negative.

Remember it's negative ground so you want to avoid using positive wires longer then they need to be because there is all this truck metal where a short could start.

 

Here this came up in a different thread where the person will have a excessive number of wires to identify. What to do? Each wire a different color would be very expensive so the easy way is use wire numbers. So you mark your print then transfer those numbers to the wires you will use. How it goes is any wire that is the same is the exact same number regardless of how many devices it's connected to.

When it goes threw a device then the number increases by one.

IE: See attached drawing.



Trap that simple. Don't need labels for that simple drawing. That is only about 1/30th of the print. Just one corner I copied off to post on this thread. Oh it needs numbers alright.
A million colored wires instead of numbers will be way more expensive. The easy way is just get one color for each size, and a different color of each size for grounds. The ground spools can be smaller because you generally don't use as much..

How to do it properly cheaply with numbers

Pick up a roll of white electric tape to temporary mark the numbers while it's getting pulled in.

Buy yourself a couple of lengths of white and clear heat shrink. They come at a electronics supply in three foot lengths. Get yourself a really good permanent marker extra fine. A permanent black Staedtler overhead projector pen works great. Cut off a inch of white and mark the numbers on it. Best to underline 6's and 9's Stick it on. shrink it.

Cut 1.5 inches of clear and shrink it over top. The small wires 1/2" inch white and 1" inch clear lengths would be enough. Mark your numbers both sides so there easier to find and don't forget to underline numbers that will need it. Take the temporary label off. What you want when it's done is the permanent labels to be about 6 inches away from where they connect so you can find them if you need to trouble shoot at some later date. Like it all seems to be so much work for nothing when your wiring it up. Problem comes three months later when you can no longer remember which wires goes where. Then your doomed. If you number them and have the print anyone can fix it at any time no problem. If there not numbered your screwed and repairs could be very time consuming. You can actually buy packages of numbers but there not cheap and if you want them to last you need the clear heat shrink too on a truck. Otherwise in a week you'll never be able to read them.

Cars generally use colored wires for numbers. You'd need thirty colors and several sizes. Not worth it. Planes use just white wire and labels. In the electrical trade we mostly use numbers and very few colors. Colors designate what type of power and not where they run for electricians.. We use numbers for that.