: fuse block and relay question


cooper4x4
02-09-2006, 05:37 PM
Currently I have an auxillary fuse block bolted to the firewall for all of my accessories (lights, CB, etc). To clean up the engine compartment and to protect it from the elements, I want to move the fuse block and all relays into the cab somewhere and run the wiring under the carpet for the accessories. My intial thought is to mount the block and relays behind the rear seat of the DC on the "cardboard" rear wall. I think a bolt with a washer on the back should be able to hold everything. If not then I could add a piece of sheet metal behind the "cardboard" for extra support. I could run a ground wire out the rubber grommet on the rear cab wall and ground it at the frame.

Does anyone see a potential problem with this setup?
Anyone else have any possible suggestions?
Thanks.

jessevic
02-09-2006, 06:18 PM
I put my fuseblock for my sat radio/stereo/deck/etc in the space created when I went from the stock 2DIN deck to a clarion DIN deck. There is quite a bit of room back there, the only problem is that it isnt that easy to access quickly. Just an option for you.

hk'dontoys
02-09-2006, 06:29 PM
why can't you just seal the fuse block and leave it where it is? seems like such a lot of work especially when there is more stuff than that to worry about from submerging in water if its not protected.

cooper4x4
02-09-2006, 06:40 PM
The main reason I want to do it is becaue I have at least 5 power wires going through the rubber grommet in the firewall, probably more than that. I want to change that to just one power wire. Things just need to be cleaned up.

Dick Foster
02-09-2006, 06:43 PM
Why would you use a rubber grommet on a ground wire? Just ground it to the cab. LOL

cooper4x4
02-09-2006, 10:04 PM
There are not too many bolts in that area of the cab to ground it to. I would rather not drill any holes in the cab and figured it would be easier to run it to the frame.

cooper4x4
02-10-2006, 09:41 AM
Ttt

Dick Foster
02-10-2006, 02:05 PM
Well make one then be sure to scrape away some paint so you get a good metal to metal contact. Then do what I did and beef up the ground wire from the battery to the chassis and using some heavy braid or welding cable, I also made a ground connection from the block to the frame. What will welding on it all the time along with the extra lights, compressors and what not, good grounding can't hurt, especially in an EFI vehicle. It's easy to do and cheap insurance to make sure that you have a good solid ground system to run all of that stuff with.

Bear
02-10-2006, 02:29 PM
Brad, one thing you might want to conside is that you want your fuses and relays as close to your power source as you can get them. Less chance of over heating a wire that way which if you let get too hot will ignite.

Funny how you and I seem to be shadowing each other on projects. After I get the stuff I am working finished, I was going to start installing a fuse block to clean up the battery area as well.

cooper4x4
02-10-2006, 02:30 PM
I would use heavy gauge wire for the main power to handle the power load. I don't think I will have a problem with wires overheating. Just an FYI, www.12voltguy.com sells some nice fuse blocks for pretty cheap.

Bear
02-10-2006, 02:35 PM
Thanks for the link I need to book mark it for future reference.

What I meant (and as soon as I hit the post button knew it was not clear) about keeping your relays close to the battery is this. You get a constant voltage from a 12volt source, but think about if you did not have a relay between the battery and the accesory? What would could happen? If you have the relay close to the battery you more of the proper voltage flowing to the accessory for the longer distance.

Hell I know what I mean just can't explain it. Dick should be able to describe what I am talking about better than I can

Here's the Pitch Dick! hit out of the park for me!

Dick Foster
02-10-2006, 05:06 PM
I think what you're getting at is what is called IR drop. It the voltage drop across the resistance of the wire. The smaller the wire diameter is the more resistance it has (R is Resistance bit) and the longer the wire is the more resistance it has so more poor is lost (that the drop part their talking about voltage but it's really power) the higher the current is (I is the current part) and the smaller and or longer the wire is . P=EI where P is power in watts E is voltage in volts and I is current in amps and P=Isq.R. Let's say you have a wire of a certian gauge, say 20 gauge at .0119 ohms per foot. Say you're gonna run some rocks lights for the rear wheels and they are 55 watt lamps. For two lights that's 110 Watts/14 Volts (the truck is running) = about 7.9 amps that the lights want. Say that 20 gauge wire is 15 feet long so that is about .2 ohms of resistance from the wire. That works out to about 12.5 watts of power lost to heat in the wire. The wasted power drops the voltage to the lights so the lights aren't as bright either by roughly 10%. If you used 16 gauge wire instead the resistance is .00473 per foot or only 0.07 ohms which is less than half of the resistance the 20 gauge had.

Wire Resistance
Gauge per foot
4 .000292
6 .000465
8 .000739
10 .00118
12 .00187
14 .00297
16 .00473
18 .00751
20 .0119
22 .0190
24 .0302
26 .0480
28 .0764

And the other way of looking at it is Copper wire resistance table AWG Feet/Ohm.
This is for round a trip i.e. both wires pos and neg. Double the distance for a positive lead and a chassis return if you have and use good grounds.

10 490.2
12 308.7
14 193.8
16 122.3
18 76.8
20 48.1
22 30.3
24 19.1
26 12.0
28 7.55

Ideally the relay would be at the load or close to the lights in this case. That way the relay contacts (they have resistance too) doesn't have to dissipate the power that is wasted in the wires. Practically speaking that's too much wireing to wire the supply leads and the coil so just put them where they are easy to get to.
Use the largest wire you can and put a fuse close to the battery or power source. The fuse is there to protect the wire from getting hot and setting fire to your truck. I won't help much if the fuse is somewhere after the short circuit to ground because the fuse won't blow and the wire will just continue to heat up and destroy stuff and maybe set the truck on fire in the process.

Size the wire for the load and wire length and size the fuse to the wire size and again put the fuse close to the battery so you don't burn your truck down.
It's OK to run a large wire with a big fuse that's close to the battery to feed an aux fuse block with smaller fuses that then feed various stuff like lights and compressors. I have one mounted under the hood on the passenger side firewall. It is feed from the battery with 8 gauge wire and is protected with a 40 amp fuse. The aux fuse block feeds the rock lights (3 pairs/3 fuses) the air compressor (20 amps), underhood lights (2 amps for LEDs) and soon some a couple of line locks at about and amp each.

cooper4x4
02-10-2006, 06:48 PM
Dick, I want to get two of THESE (http://www.12voltguy.com/catalog1.0.html1.0.html) and mount them in the back. I planned on running a 8 gauge power wire to the blocks and splicing the wire to go to both blocks. I will be running 4 offroad lights (2 are 130W KCs, other two are walmart lights), 4 rock lights (55W ea), Cobra CB, and Ford Taurus elec fan. How big of a fuse do you think I would need on the main power wire? Would a circuit breaker work better than an inline fuse?

SAR_Squid79
02-26-2006, 11:41 PM
I just got the lights that I'm gonna mount to my DeMello light bar in my bed. I'm pretty good with mechanical stuff but I know dick about wiring or anything electrical so I have a question:
I have a Auxillary Fuse block, and I got a fused relay with the lights. I'm trying to figure out how all the components link together. I know that the purpose of the relay is so you don't overload and burn up the switch, and that it should be wired where the switch is basically turning the relay on and off, but I'm an idiot when it comes to this shit, and I just can't seem to visualize how I'm supposed to wire it up.

Fuse Block, Relay, Switch, and lights.

The switch I have has 3 pins. 1 goes to ground, 1 goes to the battery (or in my case the fuse block), and 1 goes out to the lights. Does the relay go in between the lights and the switch, or between the switch and the fuse block, or do I not even need the relay since I have the fuse block?

SAR_Squid79
02-27-2006, 08:26 PM
I just got the lights that I'm gonna mount to my DeMello light bar in my bed. I'm pretty good with mechanical stuff but I know dick about wiring or anything electrical so I have a question:
I have a Auxillary Fuse block, and I got a fused relay with the lights. I'm trying to figure out how all the components link together.

Fuse Block, Relay, Switch, and lights.

The switch I have has 3 pins. 1 goes to ground, 1 goes to the battery (or in my case the fuse block), and 1 goes out to the lights. Does the relay go in between the lights and the switch, or between the switch and the fuse block, or do I not even need the relay since I have the fuse block?
BUMP!

SAR_Squid79
02-28-2006, 06:46 PM
:mad: Damn It! Can Somebody Answer My F-ing Question!?!?!?!?!?! :mad:

I know it's a moron newbie question, but C'MON!

Fezzik
02-28-2006, 07:51 PM
The switch I have has 3 pins. 1 goes to ground, 1 goes to the battery (or in my case the fuse block), and 1 goes out to the lights. Does the relay go in between the lights and the switch, or between the switch and the fuse block, or do I not even need the relay since I have the fuse block?
You are correct on the 3 wires to the switch. As for the relay, The wire that goes from the switch to the lights actually goes to the relay. you also have a separate power wire the can come directly off the battery to the relay and one that goes to the lights.

You wire up the relay this way to prevent the switch from having more power than it can handle going through it.

Here is a good site that explains it (http://www.armchair.mb.ca/wings/relays/index.html)
Sorry found a better site

jessevic
02-28-2006, 07:54 PM
Hahahahah.... heres my best attempt at an ASCII wiring diagram.



PS
|
FB
|
S---G
|
R---FB---PS
|
L---G
|
G

PS=power supply
FB=Fuse Bloc
S=Switch
R=Relay
G=Ground
L=Light

There is only 1 power supply, I just couldnt figure out how to draw it. And make sure you are using 2 different size fuses. The switch only needs a small fuse, and the Relay will need as big of a fuse as the Lights require.

BajaXplorer
03-03-2006, 03:21 PM
http://www.kchilites.com/faq/instructions/4-PoleRelayDiagram.pdf
http://www.kchilites.com/faq/instructions/6315_RelayHarness.pdf

SAR_Squid79
03-03-2006, 03:48 PM
http://www.kchilites.com/faq/instructions/4-PoleRelayDiagram.pdf

THANKS MAN! :kewl:

That's EXACTLY what I needed to know! Awesome, perfect diagram! :D

flyingwil
03-03-2006, 07:21 PM
I am using a fuse block to be mounted in the tool box (with a second battery), to support the full time power requirements. It is a Blue Sea block (http://www.westmarine.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10001&langId=-1&catalogId=10001&productId=91545) from West Marine. These are really nice units, and a bargain compared to the Painless Fuse block units.
http://www.westmarine.com/images/full/fuseblock_f.jpg

They have complete + and - terminals and supper easy to use. I have toyed with installing it behind the rear seat, and using a audio amplifier kit to power the unit. You can pick up an istall kit for Wal-Mart for cheap with a heavy duty inline fuse, and gounding cables upto a 4g. wire.

porkysan
03-04-2006, 05:48 PM
I've got that exact fuse block from bluesea.....it's great. I had mine for a while before finally getting around to installing it. I still need to add an inline fuse....it's being shipped as I type.

The 12 spots are probably overkill for me.....but I just didn't want to have to do this again in a few years.


I just need to go back and clean up some wiring now from other stuff that I installed prior to this block(lights, CB, an aux. outlet)

waskillywabbit
03-04-2006, 06:15 PM
I have (2) of those Blue Sea fuse blocks and one of their marine battery switches...top notch stuff for a lot less than some other equivalent equipment.

:welder:

wisctaco04
03-05-2006, 05:28 AM
:mad: Damn It! Can Somebody Answer My F-ing Question!?!?!?!?!?! :mad:

I know it's a moron newbie question, but C'MON!
Just drive up here and we'll wire it up.