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View Full Version : Wiring Questions - Fuses, relays, lights and switches



offthebeatenpath
02-04-2012, 01:31 AM
So. After spending entirely too much time reading through threads that half answer my questions, I thought I'd try to consolidate some answers in one thread.

2003 DC Tacoma, 3.4, blah, blah, blah.

It has one set of cheapie 55w driving lights wired in up front.
This weekend I'll finish up color matching the paint on my topper to my truck, and reinstalling it. Once it's installed, I'm going to want the remotely switched rear end lights I've been holding off on doing, so I'd like to get them done this weekend. That would give me two sets of lights, relays, fuses and switches. It seems like there must be a simpler way to do this than having a rats nest of wires under the hood. There also has to be a cheaper way than purchasing an sPOD (http://www.4x4spod.com/product_p/800-000-000.htm). The hitch is this- I understand enough of wiring to handle wiring in the second set of lights without staring at an instruction sheet the entire time, but not enough to design what I'd like to see under my hood.

I'm not sure if I've overlooked something that I should be, but I've read a number of threads on the Blue Sea auxiliary fuse box, as well as reading through most of what is on Stu's (http://www.stu-offroad.com/electrical.asp) page (excellent resource by the way).

I have an auxiliary fuse box, I picked up a covered 6 slot blade fuse box from Napa, and I want to set it up in such a way that it looks clean under the hood. What I'm wondering is how do I properly power that fuse box, and how do I cleanly wire relays into the system? Is that even possible with multiple wires required by the relays? How does the Blue Sea box differ from THIS (http://www.globalindustrial.com/p/tools/vehicle-maintenance/battery-service/battery-doctor-ato-atc-6-way-fuse-block?utm_source=google_pr&utm_medium=cpc&utm_campaign=Battery-Service-google_pr&infoParam.campaignId=T9F) box except that it's much cheaper?

TACODOC
02-04-2012, 02:29 AM
http://www.tacomaworld.com/forum/technical-chat/103969-electronics-basics-reference.html

http://www.the12volt.com/

HillbillyfromAL
02-04-2012, 07:54 PM
To power your fuse box you need a thicker cable that is fused that can handle the combined load of the box. To make it simple if you install a switch it needs to go to a relay. Most switches aren't designed to handle much amp draw.

offthebeatenpath
02-04-2012, 11:39 PM
Well, I also answered one of my own questions- turns out the fuse block I bought is not a "sub-panel" it simply holds six fuses with in and out connectors on each side. Looks like I'll be looking for a Blue Sea block.

Thanks also for the Tacoma World link- that was perfect. Easy reading, easy to understand. Excellent help.

downhill
02-05-2012, 04:22 PM
The Blue Sea panels are very good. They offer both fused power distribution and a ground buss. Mine is powered through a HD relay and triggered by an ACC wire. It's cold when the key is off.

offthebeatenpath
02-05-2012, 06:18 PM
downhill- I'm curious, why did you opt to run everything by ignition on only?
I've mostly been thinking that I'll run everything direct off the battery, so I have the option to flip on the lights without the keys.

I think I will go with the Blue Sea panel as well, I just have to get my hands on one.
I've got my back-up lights mounted and wires run, I'll post them in my build thread sooner or later....

cam-shaft
02-06-2012, 03:10 AM
I prefer to go with re-set breakers, over fuses. Especially for accessory power options. No need to search for fuses just re-set the breaker. Also run a main manual trip breaker that is equal to whole system amp draw and powers up complete accessory system. You can shut down main breaker to shut down all accessory power. All marine grade breakers and wiring for excellent water protection. Good reason to have accessory power hooked to accessory battery. If running accessories with truck off and battery goes dead just start truck off of main battery.
http://i977.photobucket.com/albums/ae259/cam-shaft/apmbreaker.jpg

downhill
02-06-2012, 03:55 AM
downhill- I'm curious, why did you opt to run everything by ignition on only?
I've mostly been thinking that I'll run everything direct off the battery, so I have the option to flip on the lights without the keys.

I think I will go with the Blue Sea panel as well, I just have to get my hands on one.
I've got my back-up lights mounted and wires run, I'll post them in my build thread sooner or later....

I have a couple of things like a work light wired direct, but the majority of the things I power only need to run when the key is on. The idea is that the fewer hot wires you have the better. Less chance of a short taking the battery down. I don't run dual batteries.

offthebeatenpath
02-12-2012, 03:23 PM
Here's a couple quick questions from this weekends work-

1- What would be the advantage to having a Blue Sea block with positive and negative terminals, versus only having a positive terminal?

2- Has anyone successfully wired in the relay for an accessory light into the factory fuse and relay panel under the hood? I noticed that there are two open relay spots, but didn't look much further than that.

3- What is the advantage to running a 5 pin relay versus a 4 pin relay? I was looking for relay sockets with leads and noticed that most that I found have five leads for a 5 pin relay. Why for?

downhill
02-12-2012, 10:30 PM
#1 Having both a ground and power block makes wiring easier because good grounds are hard to come by in a truck with so much plastic. Years ago everything was metal and everything was a ground path

#2 Haven't tried and don't know. I try to stay clear of the factory harness with my upgrades. On these trucks it's easy to power a ground circuit accidentally and cause all sorts of crazy things. You turn on the wipers and the dome light starts flashing, things like that.

#3 The 5 pin relay switches between two outputs when the relay is powered and off. Terminal 87a is powered when the relay is off and 87 is powered when the relay is "on". The 4 pin is a simple on and off. Relay on = powered circuit on, relay off = powered circuit off. You can use a 5 pin in the same way by wiring the powered circuit to the 87 terminal and leaving 87a blank. 99% of the time all you need is a 4 pin.

Utah KJ
02-13-2012, 03:28 PM
The issue with breakers for 12V use is almost all of them operate on heat which makes them inline resistors which is not great for current delivery. Fuses are much better, just carry spares.

LandCruiserPhil
02-13-2012, 11:33 PM
The issue with breakers for 12V use is almost all of them operate on heat which makes them inline resistors which is not great for current delivery. Fuses are much better, just carry spares.

Upgrade to automotive BUSS breakers(made in the USA:)) and never look back. Used them for almost 20 years with great results. Loss is almost zero (.04 volts loss loaded at 10A) voltage loss measured with a Fluke meter. I use them when wiring our Trophy truck and never a failure. The best part in the event of a fault they will auto reset once the fault is cleared. Nothing better for 12volt outlets in my experience. Where I do fine measurable voltage loss using cheaper constant duty solenoid and relays. I try to use rated switches rather then cube relays when possible. I find them more reliable and a lot less to go wrong.

cam-shaft
02-14-2012, 03:58 AM
The issue with breakers for 12V use is almost all of them operate on heat which makes them inline resistors which is not great for current delivery. Fuses are much better, just carry spares.

Just thought I would do a quick check of 1 accessory system on my truck to give you some factual info. Running 1 system on my truck that has a 15amp carling tech breaker I showed a .08volt drop. The system is pulling close to 15amps. I went ahead and plugged in a fuse to that same system instead of the breaker and checked my voltage drop through the fuse and I showed .09volts. Is either one of these enough to cause an issue? No.
I went ahead and did 1 more test with the 15 amp Carling tech breaker and the simple 15 amp spade fuse. I checked the resistance value of each. They both came to .1-.2ohms of resistance. What does that mean? It means, in theory, the voltage drop should be the same if there was no human error factor of connectors, etc.
Really the issue with most electrical systems that cause excess voltage drops is the human error factor. It is the poor connections and connectors people make and use, the wire they use and how bad the elements effect these issues, corrosion, etc.
Putting together a circuit breaker system takes a bit more for-thought, time, and cost but the end results are worth it to me. I would have to say I have sent more voltage to amp draws in harsh environments then I could begin to explain.
Cam-shaft.