by "BJ" (benjamin-bignell)
Published 03/26/2017 at 10:46
by "BJ" (benjamin-bignell)
Published 03/26/2017 at 10:46
Tags: electricity
STARS: 1
I’m looking to add some new circuitry to the 4Runner, and I’ve got some questions.
First, is the circuit breaker (or a fuse) necessary before the panel?
Second, is it a big deal if the radios aren’t fused as close to the battery as possible? I’m going to be reusing the wiring that they already have, which means using whatever inline fuses they have - these are usually very close to the device itself.
Third, how do we choose what gets used as the “ignition hot” wire for the relay? I’ve got the wiring diagrams for the truck, but I’m not sure I understand them well enough. Note that the relay will likely be two separate units, I just used a DPDT for convenience in the drawing.
Any help is appreciated! Let me know if you see something terribly wrong with my plans.
Update: the 4 AWG wire limits me to 70 A or so, even if the box can handle up to 100 A (max 30A per circuit). I’ll see what the price difference is, and if it’s practical to use 0-gauge here or not.
"benjrblant" (benjblant)
03/26/2017 at 11:01, STARS: 2
1) If the fuse panel is mounted practically on the battery box, you could probably get away without a circuit breaker. If the fuse panel is mounted further away, such as in the cab or rear of the vehicle, you’d absolutely want a circuit breaker. Reasoning is that if there’s a short in the wire due to aged insulation or a car collision, an unfused section of wire with a short is a recipe for big problems including a potential fire. Having said this, use of a properly sized circuit breaker is always a good idea.
2) Probably ok as these use relatively little amperage. Is there a reason for not running the radios through your blue sea fuse block and going straight to the battery? Generally, I’d advise against wiring things directly to the battery as it rapidly turns into a rats nest of wires and becomes increasingly difficult to troubleshoot.
3) Not sure I have any sound advice here. Ignition wiring can vary and I’m not familiar with the 4runner. Which gen/year is this?
"MM54" (mm54mk2)
03/26/2017 at 12:04, STARS: 1
I would definitely recommend a breaker, fuse, or fusible link as close to the battery as possible - the last thing you need is something to melt in the fuse box and set the interior on fire because it’s now only current-limited by the wire feeding it. Similar goes for anything you’re wiring - put the fuse as close to the source as possible as to have minimal unprotected (or under-protected) wiring.
I would consider running the radios off the same fuse box - even if they’ve already got an inline fuse, it will tidy up the wiring considerably. No harm in having two fuses on the same circuit.
Your third question is often the hardest part - honestly the best bet is to check out the wiring diagrams for what you think should be ignition-on and go after it with a multimeter and check to make sure it’s on only when you want it.
Did you make the wiring diagram above? If so, bonus points for using the correct ‘ground’ indicator on the relay coil.
"HammerheadFistpunch" (hammerheadfistpunch)
03/26/2017 at 12:05, STARS: 1
Yes, no, cigarette lighter hot
"HammerheadFistpunch" (hammerheadfistpunch)
03/26/2017 at 12:08, STARS: 1
Rf interference. You generally want to isolate at least the ground direct to battery for minimal rf interference
"vicali" (vicali)
03/26/2017 at 12:46, STARS: 0
Haha,
You’ll also find that door locks are one of the only always hot circuits. Everything else is either switched with acc, or on with the engine.
You have a meter right?
"BJ" (benjamin-bignell)
03/26/2017 at 13:10, STARS: 0
It’s a 2005. I’ve got the full wiring diagrams from Toyota, I just need to decipher them.
My question was more about what is an appropriate wire? I can’t just run 12V from the battery to ground through the relay, or is there a resistive load built in?
"BJ" (benjamin-bignell)
03/26/2017 at 13:12, STARS: 0
My cigarette circuit is borked. There’s a short somewhere and I’ve decided to just pull the fuse.
I’ll just tap some other circuit off the fuse panel in the cab.
"BJ" (benjamin-bignell)
03/26/2017 at 13:12, STARS: 0
Yep!
"HammerheadFistpunch" (hammerheadfistpunch)
03/26/2017 at 13:18, STARS: 0
That works too
"BJ" (benjamin-bignell)
03/26/2017 at 13:30, STARS: 1
The radios go straight to the battery to reduce radio-frequency interference.
The new fuse panel goes under the hood - it’s supposedly watertight, for marine use. I’ll pick up the breaker just to be safe.
And yes, I drew the picture. :-)