wiring, fuse box, lights, wiper

Hi.

I have some quick questions for you guys.

1. Is correct if you wire the right side of a fuse box with 12v wires and from the left side you take them to the relay?

2. Can you wire the front and rear lights on a single 40A relay? The lights will work properly? Is the switch wired good?

3. When you are wiring the wiper motor and the brake light is it recommended to use a relay? Or a simple fuse will work just fine?


Made this in paint to give you an idea about what im talking! Please excuse me if the questions are stupid but i dont have any training and I want to learn .




Cheers!

Anytime you connect an accessory or lights or anything to 12v, it should ALWAYS be fused no matter if a relay is used or not.

A relay is used when the switch you are using is not capable of handling the amperage or power needed for that device. Or to reverse the polarity needed (from negative to positive) such as in your picture.



-------------

Well said shortcircuit161.

turboturtlee - don't confuse "protection" like fuses and circuit breakers with switching - eg, relays.

A fuse is there to protect its downstream distribution (wiring) in case of short circuits etc.
The fuse must therefore be rated equal to or less than the cable/wire and switch/relay etc rating. (EG - if a 50A fuse protects a 40A cable and a 30A relay, the cable or relay may melt or cause a fire before the fuse blows.)

As shortcircuit161 wrote, relays are used to take the "load" off the switch(es).
Relays also mean that smaller switches (or less powerful electronics) can be used as well as more direct heavy-current cabling.
For example, older cars had wiper and light switches in the cabin/dash. That meant a heavy cable to the switch and back to the load (wiper, lights), and a heavy-rated switch.
These days relays are used instead. Hence the heavy current-carrying cable need only run from the battery (thru fuses!!) etc thru the relay to the load. Only a small switch is needed with smaller wires to the relay coil.
Hence also lower voltage drops to the load due to shorter power runs or because heavier cable can be used, and relay contacts usually stay cleaner than mechanical cabin switches (dirt & wear = resistance, hence heat and failure).



FYI - by convention the more +ve goes to relay coil #86 - ie, +12V to #86 and the 0V/earthed/ground wire to #85.
But that is by convention and only important if you have a relay with inbuilt diode snubber to prevent voltage spikes. Most relays don't have internal diodes though many these days have an internal snubber resistor, but they don't care about their polarity. (I prefer normal (non-diode) relays and instead add my own external diode if needed.)   


And incidentally, your relay circuit is a classic horn-relay circuit - a grounded button triggers the relay which connects +12V to the horn.   3-pin horn relays that internally joined #30 to the coil were once common.
Also wipers were often the opposite - their motor was connected to +12V and the relay connected motor winding(s) to ground, usually from a +12V switch.

Stick to shortcircuit161's reply if this has confused you. Your circuit is quite ok (provided you don't use a relay with internal diode).


PS - "distribution fusing" like yours is separate to "equipment protection fusing" as used in amplifiers etc. You may have a 30A fuse and relay and wiring to a 10A amplifier or HU and that's fine. The equipment protection fuse will be at the equipment end - ie, the 10A fuse in the radio/HU/amp, or just before it. [Though it could also be the same wiring with a 10A fuse "up front" (ie, at the battery end instead of at the load/equipment end) that replaces the 30A fuse. But that's provided no-one ever changes the size of that front 10A fuse assuming the load doesn't have its own, but then a bigger 20A or 30A fuse should be used instead - ie, blow one fuse, not both.]

Thanks for replays!

I had a feeling that the relay was some kind of safety feature who takes power and lets it flow smoothly through the entire circuit.

Wired the switch that way because I thought is a lot better if you don't have 12v constantly at the button or through the circuit.

Here is a previous diagram that I was working on,any advice?
https://img528.imageshack.us/img528/2314/dswd1v1.jpg




Cheers!

Your link just sends us back to this thread.
In at right side, out left?
Never heard of that one before.
Neatness, weather and corrosion protection are far more important.
SS and Oldie called it correctly in fact ex factory most side light circuits have TWO equipment fuses after the relay output, one for left and one for right OR one for front and one for rear.
The question about coil pins on a relay;
When they are dioded ex OEM, 86 is ALWAYS the positive side by ISO convention/standards therefore I always use it as the POS.
Frankly unless you're using a 5 pin (87a) relay as a changeover in practise it doesn't matter which way round 30 and 87 go.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

howie ll wrote:

---

Your link just sends us back to this thread.
In at right side, out left?
Never heard of that one before.
Neatness, weather and corrosion protection are far more important.
SS and Oldie called it correctly in fact ex factory most side light circuits have TWO equipment fuses after the relay output, one for left and one for right OR one for front and one for rear.
The question about coil pins on a relay;
When they are dioded ex OEM, 86 is ALWAYS the positive side by ISO convention/standards therefore I always use it as the POS.
Frankly unless you're using a 5 pin (87a) relay as a changeover in practise it doesn't matter which way round 30 and 87 go.

---

yep,sorry I'm not that good expressing my self. Just copy/paste the link in the search bar and it will work I've wiried the relay correctly I think, pin 86 is POS.

Instead of putting one fuse for front and one for rear , can you just put one fuse after the relay for the entire circuit?

Cheers!

Yes its a throwback to those wonderful(?) old days of the 50s and 60s when cars had non-halogen headlights and drove on sidelights.
you still had some lighting if one side or end failed.
Even today the left and right headlamps have individual fuses.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

BTW what are you doing?
Are you trying to build a roadworthy vehicle because in that case you'd damn will better fuse everything.
And your relay was quite correct.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Thanks!

Well not exactly roadworthy, for rallycross to be exact, I want to remove all the OEM wiring and replace it with this basic layout.

Ok, so two more 4way fuseboxes for front/rear.

Another question, what should I use between the bat. and fuse box? an 80A Maxi fuse or 150A Mega fuse, how do you calculate what kind of fuse do you need?

You won't need it.
The fuse box should cover all your consumables plus alternator and say 70 amps for the starter motor.
Oldspark may have some answers when he comes back on line later tonight our time.
The calculation is worked out from the known load + up to 5 amps depending on distance from source.
Back in our audio days, a rear mounted amp with a 30 amp inbuilt fuse got a 40 amp at the battery.
Fusebox rule, not to exceed 12" (30cm) from the battery +.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

Look at UK sites such as I believe raw power for fuseboxes and relay holders.

-------------
Amateurs assume, don't test and have problems; pros test first. I am not a free install service.
Read the installation manual, do a search here or online for your vehicle wiring before posting.

My vehicle is from 1965 - the days of heavy dash switches for lights, wipers etc and no alternator to battery fuse.
The only relays were for the horn, and the starter motor. The latter was handy - they kept it despite changing from the older direct-powered Bendix spring starter to the newer typical solenoid actuated "throw-out" starter. But it can be manually closed like many English starter relays could be. That's very handy for engine tuning, getting out of bogs etc.

Despite good headlights for the time (4 round tungstens), I converted all (my 1960's vehicles) to halogen with - of course - relays.

The typical 25A externally regulated alternators (or generator LOL!) are now modern (1980s/1990s) all-in-one alternator/regulators typically of 75-120A.

I decided too that the original four 3AG glass fuses weren't ideal(!!) although 3 are still in use; the 4th being the 30A for the lighting having long ago lost clip tension from heat despite its load dropping to mere parkers and cabin and 4 relays coils (the headlights being moved to separate cables, fuses & relays).

The only change from my early competitive rally days is the modern alternator. (Replace older externally-regulated types if you can.)


Probably my biggest PITA was battery terminals. I run several loads with dedicated cables from the battery - eg, HU/audio, "ignition" relay (for dash voltmeter and a few other things), and optional 2nd battery.
I was cursing a few years ago after finally finding great & cheap "satin finish" terminals with extra cable takeoffs only to soon afterwards change my "master fusing" technique. Actually I didn't have master-fuses at that stage - aka fuse-links or flinks - but it had been a long desirable feature. (Besides, the OEM fuse box above the firewall was diagonally opposite the front mounted battery - relatively a long distance and easy for a short to occur - not that I've ever had one.)

I now use a 3 flink box that mounts directly onto the +ve battery terminal. They are/were used in many Toyotas though I used one from a Hyundai (I think) because its centre flink could be independent of the common +12V battery supply, and all flinks were pluggable & not bolted. (I wired that between the alternator and headlight relays. In ye old days at least, headlight power was taken from the alternator for that bit of extra voltage.)

I did rewire it recently. The headlights are now taken direct from the battery +12V as is the audio and aux battery.
The 3-flink box still has the "master" flink for the rest of the vehicle and the other 2are in parallel between the batt +12V & the alternaor.
Yes, I avoid parallel fuses, but in this flink box all flinks are pluggable (unlike some like Toyota where the centre flink is bolted) and despite pluggables being available up to 80A, I limit them to 40A s a result of a melting experience. So I use 2 flinks because IMO 40A isn't sufficient for the alternator, and another in parallel halves the resistance, and in my case suites the 2-cables from the alternator.   
And not that I believe in alternator to battery fusing per se, but until it causes an issue, I'll do what the moderns do. (That fuse is only to protect the cable (and battery) from an alternator-end cable short, but I never had problem with mere physical security.)

FYI - the headlights come thru another 2-flink box with bolted flinks (50A or 60A or 100A?) one each for high and low beams (or was it left & right?). They feed the individually fused low & high beams. I reduced to 3 headlight relays as part of the recent rewire, but intend to return to one relay per filament (6 relays) - it's much easier for aiming purposes, and it overcomes the dilemma of whether to "master fuse" the headlights into left & right, or high and low. (Left & right being the more modern.)   


One BIG change is that my headlight fuses are now all self-resetting circuit breakers. It's not that important now with individual fuses & relays, but how insane that originally ALL the lighting went thru a singe fuse - shortcircuit a taillight and you lose all headlights. And everyone knows that only happens in excess of 160kmh around dark tight bends.
BTW - those headlight flinks are purposely rated MUCH higher than the downstream loads & breakers. They should never fuse (open) and are only there in case of a bad wiring failure - ie a short to chassis before the relays. But even if that happens, I still have the other lighting circuit.


Sorry for the ramble, but you mentioned rallycross!
And I was intending sample pics of the 3-flink box etc. (If you're still interested....)

BTW - I like the plastic flinks. Old wire flinks are stupid (too thinks that's the was I was going to go!)
And I never likes Maxis though I recently got some for free from some French car at a wreckers including some self-resetting breakers Maxi breakers (60A). But I still don't like them.
I prefer common blade/spade types like ATS and the plastic flinks. In fact I recently decided to go micro-ATS with micro-ISO relays in the future.

quality post,oldspark!

now I have a clear idea about what i need to do, if I will have some question regarding alternator or starter motor wiring I will post here.

I'm gonna try to keep you guys updated with everything!

last thing

howie ll wrote:

---

Fusebox rule, not to exceed 12" (30cm) from the battery

---

why is that? I know that some cars have the battery in the boot,so thats more than 12" from the fuse box.



Cheers!

Ah - but that boot battery MUST - or should I say shall (with its Aussie legal meaning) - have its own fuse.
And BTW - EACH battery is to have a fuse or fuses. Many with dual or multi-batteries only have one, and one is required AT EACH battery (except when physical protection applies, but more on that later...)

As to within 12", there is no such specific rule per se, but 12" and 18" are two distances often quoted.
The real rule is essentially "fuse it before (where) a short could occur" but bear in mind other rules or recommendations like not in the gassing zone of a battery or other explosive atmosphere, and the classic - make sure your protection (ie, fusing) does not itself cause a hazard!



Alas I've written this sort of rambling treatise before, but maybe another "top down" but brief paraphrasing to help clarify:

All electrical power sources should employ (downstream) protection (for safety reasons). [Should means must or shall.]

Protection can be physical or electrical.

Electrical protection means fuses or circuit breakers etc.
Physical means adequate physical protection like insulation or ducting AND maintenance procedures. EG - telco's with huge 48V (& maybe 24V & 12V) battery systems using un-fused copper bus bars, sometimes insulated, with metal ladders banned and warnings like "do not short your screwdriver or spanner or crowbar or equipment cubicle across these un-fused bussbars!.
Battery to starter-motor cabling is another common example of an un-fused physically protected cable/distribution.

The protection is to protect downstream distribution until the next protection.
That means that a fuse protects its downstream cable. EG - a 100A fuse from the battery for its 100A or higher rated cable until it gets to a downstream (100A rated input) distribution block or fusebox which may then have smaller fuses to protect its emanating cables.

Note the basic requirement in the last - an upstream fuse must be rated equal to or less than the lowest rated cable or relay or connector etc it feeds [until another (smaller) fuse takes over].


Damn - a part ramble. But I wanted to include some examples or clarification. I haven't included all the issues and considerations.


I wrote the above because I think of common examples where people follow the "fuse rule" yet IMO create a bigger hazard.
EG - alternator to battery cables were once NOT fused. They relied instead on physical protection. (Newer vehicles generally all include fuses.)
One the12volt poster upgraded his alternator to battery or fusebox cable with a BIG cable. But instead of having a relatively short cable from the alternator to the target (battery or fusebox), he included a fuse and thereby probably trebles his cable length.
Not that the trebled length was an issue, but it's where the cable ran to include the fuse. IMO there was far greater chance of that cable shorting before the fuse than what the direct alternator to target cable would have had. Ergo, IMO by including the electrical protection he created a hazard that was greater than NOT including it.


Note that my reply has only considered distribution protection. It does not include equipment protection, but that is usually in the device else is the last fuse before the device (but can also be ANY upstream fuse). And some equipment can't be protected anyway.


Re alternator & starter wiring, sure, anytime.
If not too late, I recommend a "2 wire all-in-one" alternator - ie, an alternator with internal voltage regulator and with an S or Sense terminal as well as the usual L or charge-Lamp terminal (often called D+ in single-wire alternators, but they have no external Sensing).
The external sensing means that the battery can be anywhere and have whatever distribution voltage drops and the alternator correctly regulates its voltage. Vehicle alternator voltages are geared to providing the voltage that the battery requires - ie, up to 14.4V.
A D+ alternator outputting its max of say 14.2V that has a 0.5V drop to the battery means the battery is only getting max of 13.7V which meas premature failure of the battery.
Mind you, a 14.4V boot battery with a 2V drop from the alternator means 16.4V at the alternator and hence maybe other car electrics which might fry them, hence good earths/grounds and distribution is essential (ie, the big-3 or 4). However many S-type alternators have an inbuilt maximum output of around 15.5V which all car electrics should handle.
FYI - except for a 6-month (disastrous?) foray into another common alternator, I have only used Japanese alternators and hence have not had the same over- or under-charging voltage issues that others have had, nor the problem of blowing main diodes on flat batteries or after jump starts.

And BTW I fitted a reduction starter motor which not only uses less current (140A as opposed to 240A), but also crankes to a far lesser voltage (eg, 5V versus maybe 8V). That was one of my better $45 wrecker/salvage/recycler investments!


Brief? Brief indeed!
Another short non-rambling reply brought to you by yours unbelievably.   

PS - I found the above mentioned link (thanks google's 3rd return to   fuse hazard alternator site:the12volt.com!)

It's this thread: big 3 upgrade on integra, fuse box?.

And it's this pic:

Finally I had the time and bought what I need to start this project.

Decided to go with a H4 wiring setup so I could have hi/low beam H4 SETUP, the plan was to use it with a 2 pole toggle switch ON(lo-beam)/OFF/ON(hi-beam).

The problem is I don't know how to add the tail lights in this combination (to light when you select hi/low), if I make a Y type conection to pin 87 i guess the circuit will allow the current to flow everywhere ending up with hi/lo/tailligts all together which i don't want.

I start thinking and got to this solution, can you tell me if it's correct and if it will work properly? Do you know a more simple way?





Thanks!

Lighting circuits are usually a 3 position switch - off, parkers (taillights, clearance etc) and beam. The beam then goes to a 2-way switch that selects hi or low beam.

Hence your taillight etc power should be taken from the wire that goes to your hi/lo switches.
The taillights etc could be powered thru a relay if your main off/parkers/beam switch is a low current unit.