Luckily the fuse went first and my switches were OK!
HTH
Nick
I'm in the process of doing the electrics now and wondered if relays are needed for the lighting or not?
All the mini's I've ever worked on don't have them, yet the Sierra and Mondeo Haynes manuals both show relays in the circuits.
I assume its to reduce current/heat draw etc in long cabling runs and where you have lots of things which draw current from the same cable,?
Anyone any thoughts on if I should wire in relays ?
Cheers
Matthew,
It depends to a large extent on what the current rating of your lighting switch is. As a rule of thumb I'd say that, if the donor vehicle (donor
of the light switch/dip-main switch that is) uses relays then you should as well.
I'm using Sierra column stalks and switches and thus I am using a pair of relays - one for main beam and one for dip beam. The side lights are
driven directly from the column stalks and I have split the left and right hand side with separate fuses. You should also use split fuses for both the
main beam and dip beam by putting the output from you r relays through a pair of fuses. That way if one bulb goes and causes a surge, blowing the
fuse, you will still have one good headlight. I once had a Mini which had complete lighting failure at night on country roads while I was learning to
drive. It is very very scary indeed as you get plunged into pitch black with only a memory of the road ahead to guide you safely to a halt!
Cheers,
Craig.
Hi Guys.
Craig's views fully endorsed - any Ford with relays is a Ford with fragile contacts in the column stalks; they do not last long without relays
especially if you decide to up the wattage of the bulbs. Better safe than sorry, also a very good idea to run separate fuses for each side - total and
sudden darkness is NOT good when going at a fair lick!!
Petemate
As above and I can confirm thast the later Sierra column switches will start to smoke in an unhealthy manner when faced with too much current.
Luckily the fuse went first and my switches were OK!
HTH
Nick
I'm with all these guys,Mini's if my memory doesnt fail me had toggle switches rated at about 25 amp.Ford stalks will carry bugger all
juice, if your using ford stalks youd need relays for sure, if not toggle switches will do it but then your into SVA territory.
Cheers,
Bob
[Edited on 10/11/04 by splitrivet]
Ditto the above comments but adding:
If the mini switches handle 25 A it's obvious it can handle 100W (16.7A) headlights? (Amended 
Thanks PioneerX)
I'd consider it imperative to use relays on an open top car - just incase they get wet. That way the fuse blows much earlier and not frying you
or the car!
[Edited on 10-11-04 by Hellfire]
Hellfire,
I think you read it wrong. Mini switches are 25A not (watts) therefore there power tolerance would be 300watts.
Either way I decided to go for relays as it just adds an extra level of protection should the column get wet. Fuse & relay are far cheaper than
replacing a burned out loom.
So have many people put fuses in-line to the lights, I'm using a premier loom and thought their fuses were enough ?
or have i got the wrong end
of the stick and you are all using home made looms ?????
Jason
I used a Premier loom on my build with Sierra stalks . came with relays and fuses, no probs ,and Alan at Premier is a very helpful guy.
Fuses are fine - it just means using heavier capacity switches and cabling usually!
quote:
Originally posted by Deckman001
So have many people put fuses in-line to the lights, I'm using a premier loom and thought their fuses were enough ?
Jason
Guys,
I am with you all 100% on using relays to reduce the loading on the column stalks, lighting switch and ignition switch but I don't believe that
you will get any extra protection from relays if the electrics get wet! Remember we are only dealing with 12 Volts which won't cause much current
to flow through pure water which is not a good conductor. Obviously the water which falls from the sky isn't pure (sadly) but even so you would
be hard pressed to push enough current through it to cause a loom to melt.
In fact, due to the fact that the relay is acting as an amplifier but taking a small control current to switch a large load, you might find that
having relays is actually a disadvantage. I say this because it is "possible" that the water might flow enough current to activate the relay
unintentionally and thus switch on your headlights or horn or something. I wouldn't lose any sleep over this mind because the chances of it
happening with anything but the most salty water would be very slim. My relay boxes which I bought from Vehicle Wiring Products (P/N RB4U) have an
o-ring seal on the lid so assuming I don't end up upside down in the rain (possible!) or submerged (less likely) then my relays should remain
dry.
Just for info, I have a 16 fuse and 8 relay setup on my locost. I'm not using all of the relays initially as I don't intend to have a
windscreen for SVA but eventually the relays will control: Main Beam, Dip Beam, Horn, Radiator Fan, Fuel Pump, Ignition Relay (To feed wipers,washers
and heater blower) and two spares for stuff like front fog lights or driving lamps or of course my electric hood
Cheers,
Craig.
quote:
Originally posted by craig1410
Guys,
I am with you all 100% on using relays to reduce the loading on the column stalks, lighting switch and ignition switch but I don't believe that you will get any extra protection from relays if the electrics get wet! Remember we are only dealing with 12 Volts which won't cause much current to flow through pure water which is not a good conductor. Obviously the water which falls from the sky isn't pure (sadly) but even so you would be hard pressed to push enough current through it to cause a loom to melt.
In fact, due to the fact that the relay is acting as an amplifier but taking a small control current to switch a large load, you might find that having relays is actually a disadvantage. I say this because it is "possible" that the water might flow enough current to activate the relay unintentionally and thus switch on your headlights or horn or something. I wouldn't lose any sleep over this mind because the chances of it happening with anything but the most salty water would be very slim. My relay boxes which I bought from Vehicle Wiring Products (P/N RB4U) have an o-ring seal on the lid so assuming I don't end up upside down in the rain (possible!) or submerged (less likely) then my relays should remain dry.
Just for info, I have a 16 fuse and 8 relay setup on my locost. I'm not using all of the relays initially as I don't intend to have a windscreen for SVA but eventually the relays will control: Main Beam, Dip Beam, Horn, Radiator Fan, Fuel Pump, Ignition Relay (To feed wipers,washers and heater blower) and two spares for stuff like front fog lights or driving lamps or of course my electric hood
Cheers,
Craig.
YOU HAVE BEEN WARNED Sorry if I went overboard - I just couldn't believe what I just read.
No offence. 
i think craig is right, myself. 12v isnt enough of a potential difference to flow thru flesh, unless you do the tongue trick - and if your tongue is
that big, you deserve a shock!
amps kill indeed, but there are only so many amps thru the starter wires cos the resistance is so low.
if you touch both terminals of a battery, you dont get a shock. 24v is a tingle. 50 is a bit more.
remember v=ir. since there is a lot of resistance between your finger tips, current is negligable at low volts.
not saying that electricity is harmless, obviously, cos it isnt. but i think craig isnt too far off the truth.
The reason you don't get a shock when holding both terminals is due to the resistance of your hands being dry.
Lets draw a mental picture:
On a pootle drive one Sunday afternoon, the weather turns a little inclemant. The rain falls into your lap, wets your jeans and proceeds to run
between your legs and gradually fills up your lovely GRP seat. Unbeknown to you the main feed to your headlight relay has fallen off and is dangling
precariously low to the shiny aluminium/steel floor.
The rain and dampness begin to everso slightly fill up the metal bath you curerntly sit in... which so by happens to be connected to the negative side
of the battery! The positive wire which has detached itself from the connector is waivering dangerously close to the floor which is now slightly wet.
But we're going slightly uphill which means the water puddle is towards the back of the car.
At the top of the hill is a level T Junction where we will be applying the brakes and the slurry of water will head towards the live naked headlight
wire....
The floor is wet - you are wet, you will become part of the electrical loop - you guess what happens...
Not scaremongering - just worried!
I am a telephone repairman and work outside in all sorts of weather. The voltage on the line is usually in the neighborhood of 24v DC and in 30 years
of working on lines in the rain I have never even felt the slightest tingle. Except, of course, when the line is ringing! Then it is 110v AC, and
that wakes me up.
dave
Thanks for that Dave - I'm glad you agree with me.
USA phone systems have only 20mA current normally at 40V though varies up to 150V. Using the negative 40V your system has proves my point nicely...
Don't want to put a spanner in the works but you ought to read up!
http://www.hut.fi/Misc/Electronics/circuits/telephone_ringer.html
[Edited on 13-11-04 by Hellfire]
Hmmm...
Not quite sure where to start with the defense of my point of view or indeed whether I can be bothered but I feel I owe it to mankind (or at least
this forum) to at least try. Hellfire, I don't wish to be disrespectful but it seems clear that electricity is not your strong point matey. I
also don't want to be a smart arse but I have a degree in electronics and electrical engineering as well as 20 years+ of practical experience in
the subject. I also used to design engine management systems for Lucas Automotive.
1. Agreed - current kills not voltage and the CAPACITY of a car battery to produce amps is very large. 20mA can stop your heart and a car battery can
produce somewhere in the region of 500A which is 25000 times the lethal current level.
2. Ohms law states that V=IR or I=V/R if you prefer. Therefore the current flowing through an object of a given electrical resistance (cable,
filament, starter motor, human body) is proportional to the voltage applied across that object and inversely proportional t the resistance of the
object.
3. Resistance of a material (steel, rubber, skin) depends on the cross section through which the current flows. In simpler terms, if you grab a little
skinny wire with your finger tips then a smaller current will flow than if you lie flat out naked on a copper plate with another copper plate on top
of you... (As you do...)
4. Human skill resistance is usually somwhere in the 100's of KOhms to 1MOhm range and thus with only 12 Volts to drive the current through this
very high resistance only around 12uA (microamps) to 120uA would flow and according to scientific studies this is likely to be below the perception
threshold of a typical human, never mind dangerous!
While confirming my values for skin resistance on google, I found this article which I
think is a good balanced piece. Note that at the end of the article the author says that 12V can in fairly specific and unusual circumstances produce
a "sensation" but is not in itself dangerous. I'd refer you to point 4 above where large contact areas can reduce resistance.
Getting back to the original argument, relays will not in any way that I can possibly imagine, protect you better if they get wet and, Hellfire, your
comment that the fuses will blow earlier if relays are fitted and they get wet is highly unlikely to say the least... A fuse will only blow if the
current flowing exceeds the rating of the fuse (ignoring vibration fatigue of course).
By the way, thanks to JoelP for backing me up on this.
Cheers,
Craig.
ps. Here are a few gratuitous 's just to keep Hellfire happy!
quote:
Originally posted by Hellfire
Thanks for that Dave - I'm glad you agree with me.
Craig - graduate or not.
Water is a poor conductor of electricity?
I would never smirk in the face of an educated person - and no electricity is not my strong point I admit freely. However, I would rather have a 5A
fuse blow on the secondary switching feed to the relay rather than a 20A fuse for the primary.
As for reaction speed - how quick can you undo a safety belt and jump out of a car?
I am not being synical or clever - a little knowledge is a dangerous thing, I understand that in it's most humbleness... I have the greatest
respect for electricity thats all. I know the basic's, maybe a bit more and that's about it. I'm not into a sh!t throwing contest -
please don't read it as such.
JoelP may have altered his opinion a little by now.... I believe
Your quote:
Getting back to the original argument, relays will not in any way that I can possibly imagine, protect you better if they get wet and, Hellfire, your
comment that the fuses will blow earlier if relays are fitted and they get wet is highly unlikely to say the least... A fuse will only blow if the
current flowing exceeds the rating of the fuse (ignoring vibration fatigue of course).
Being as there should be two fuse's that feed a relay (primary and secondary) - wouldn't the smaller of the two fuses blow first? Thereby
protecting your treasures. If there was no relay you would have a direct main feed of 20A or more... surely this would have caused much more damage
than the 5A blowing first?
I don't mean to sound direspectful but are you sure you graduated, bearing in mind your simple mistakes?
Teach me - I may learn something, but don't shout or I learn nothing!
[Edited on 14-11-04 by Hellfire]
quote:
Craig - I've never read so much bollox in all of my life!
quote:
I would rather have a 5A fuse blow on the secondary switching feed to the relay rather than a 20A fuse for the primary.
Hellfire,
Just saw your edited posting:
quote:
I don't mean to sound direspectful but are you sure you graduated, bearing in mind your simple mistakes?
More tea vicar ???
G
I hope we can speak after this - afterall I am learning more this way! I'm not being petty - well not intentionally anyway. You didn't use a
comparator such as copper (or silver dare I add!) in your previous posting's Craig regarding conductivety.
Anyhow - this all makes for a light hearted discussion on a Saturday Night - beats watching the X-Factor anyday! IMHO
I'd love a cup of tea - BTW! Maybe when I'm in Scotland next Scotlad (oh no - not again!), yourself and I could chat over a pint or
three?
So you do agree with relays then Craig All the best.... end of postings! You bite so easily!
[Edited on 14-11-04 by Hellfire]
1 sugar, not much milk thanks.
I do like an active discussion... clears the head I think!
Milk no sugar - ta!
Hellfire,
Seriously, I'm not offended and don't hold grudges so of course I will speak to you again - especially if you accuse me of talking bollocks
again...
I'd perhaps recommend exercising caution though before publicly accusing others of talking bollox, especially when the bollox they are talking
happens to be there specialist subject and not your own. I'd certainly never accuse someone like Cymtriks of talking bollox about FEA or Mark
Allanson when talking about welding. I would accuse Mr Gusterson of talking bollox but since that in itself IS his specialist subject then I
don't think he'd be offended. (Only kidding Steve!)
Anyway, my apologies to the originator of this thread (Matthew IIRC) for hijacking his thread with a daft argument. Hopefully it may have been of some
value in parts.
In summary:
Relays are good when used sparingly to remove large switching loads from delicate switches and column stalks or to allow a large and distant load to
be controlled without having to run long runs of heavy cable to and from the load which might cause voltage drop. Normally you only need to use a fuse
in the same circuit as the load itself and this should be rated according to the maximum expected current draw of the load plus a small margin.
Normally you don't "directly" fuse the coil circuit for the relay although it is sometimes the case that there will be a fuse or
fusible link between the relay coil circuit and the battery (via something like a lighting master switch or ignition switch) which will protect it,
usually along with a number of other circuits.
Finally, don't neglect to choose suitable wire for your loom if building it yourself and don't assume that the outer diameter of the wire is
a direct indication of the current rating of the wire as there are different types of insulation used which radically affect the physical size of the
wire for a given rating. I have used Vehicle Wiring Products to supply my wire and I would highly recommend the "thinwall" wire which they
can supply in countless colours and a number of ratings. The 16A stuff will be fine for most circuits but there is also 25A, 33A, 39A and 50A sizes.
Prices are per meter (1m minimum length) and range from 23p/m to 89p/m for 16A through 50A wire respectively.
VWP also supply nice fuseboxes and relay boxes by the way. I'm using two 4-way relay boxes (RB4U) and one 16-way fuse box (FBB16U) I'll try
to post some photo's when I can.
All the best,
Craig.
[Edited on 14/11/2004 by craig1410]
Only just read this thread,took a couple of minutes to stop laughing.
Handbags at ten paces!
The good thing is that both parties can still discuss ameniably,perhaps a few other people should take note of both parties good humoured attitude and
be a liitle bit more humble when discussions get exciting.
Nice one lads!!
DEAN C.....
Dean,
Thanks for the compliment - I've never been congratulated for having a well mannered argument before...
Life's too short for holding grudges - leave 'em at the front door (or the log-in page if you prefer).
Cheers,
Craig.
quote:
Originally posted by craig1410
Dean,
Thanks for the compliment - I've never been congratulated for having a well mannered argument before...
Life's too short for holding grudges - leave 'em at the front door (or the log-in page if you prefer).
Cheers,
Craig.