99176 Posted October 19, 2009 Posted October 19, 2009 I'm not much of a car 'sparky' so need a little advise. I understand it's helpfull to fit a relay before the headlights (dip and high). i) Is this protecting the dash switch or the dipswitch?ii) I've only seen relays at 70w or 100w. Are these right, as total dip is110w and high beam is 130w.I know I'm being dim but could someone enlighten me?
99176 Posted October 19, 2009 Author Posted October 19, 2009 Have just realised the relays are rated by amp, so 70a relay would be good for uprating to 100/80 bulbs yeah???
thebrookster Posted October 19, 2009 Posted October 19, 2009 P=IV, or Power = Amps x Volts.V = 12VPower = 100W (Take higher rating)Therefore I = P/V = 100/12 = 8.33 AmpsGive me 10 mins and I shall hunt out a diagram for you
thebrookster Posted October 19, 2009 Posted October 19, 2009 Quick update: what relay rating you need depends on whether or not you run two relays or not. If you run a separate relay for each bulb then you only need a 10A relay, however you can run one relay for both high beam bulbs, then multiply above answer by two to get total load on the relay. i.e. 16.66 Amps, therefore something like a 20Amp relay should be ok.Might want two relays, one for main beam and another for dip beam. Bear in mind even on dipped beam you are still running 40 Watts more power then original high beam!!Sorry, just to clarify, bulbs are rated in power (watts), and you relays are in amps as you say, hence I have used above equation to show relation.
thebrookster Posted October 19, 2009 Posted October 19, 2009 Quick schematic for wiring up.I am assuming you have a multimeter to test which cable is which for the source cables from the switch, else just unplug them!! ;DIdeally the relays should be as close as poss to the battery, in line with the lights (so there is a straight run of cable between battery, relay the headlights to minimise voltage drop). Do not worry about length of cable between switch and relay, cause this does not make much difference to operation.Also, I have not shown it but where I have put + From Battery on terminal 30 (you will see the relay terminals are numbered) this really should be a fused source, again fuse as close to battery as possible.Earths can just go to nearest earthing point.For relay, I find that Halfords do a 30A 4 pin relay that has worked fine for me on various cars I have fitted either higher power bulbs or spots to over the years.Hope this helps, just shout if you need any more info.Cheers,Phil
James Posted October 19, 2009 Posted October 19, 2009 I would say put your relays as far forward as possible and run a single big fat cable to them. I would just reuse your existing cable - if it's as per original then the wires all there and ready for you to break in to via bullet connectors.I can draw it up for you later - it's very easy and requires very little modification!James
99176 Posted October 19, 2009 Author Posted October 19, 2009 Existing cable sizes alright? Or do I need heavier duty from batt to relay 30 and from relay 87 to lamps?
James Posted October 19, 2009 Posted October 19, 2009 Have you got a new or old loom? If the wires look ok I'm sure you will be ok with standard stuff.I would put a single fatter wire up to the two relays (30 terminals) - I wouldn't worry about the 87 ones... I'm sure your standard stuff will be ok. You could check visually - if it looks ok and thick enough I'm sure you'll be fine - it's not like you are running really big power through it.
99176 Posted October 19, 2009 Author Posted October 19, 2009 And last question. Should I fuse the battery to relay 30 and if so what rating?Thanks
thebrookster Posted October 19, 2009 Posted October 19, 2009 Yup, just work out ratings with bulbs etc like above.If your lamps are either dip or main, then you will want about a 20A fuse (as that is the current draw for both bulbs together, assuming you use James' suggestion about single big cable to relays). Edit: current draw for both bulbs on main beam alone, realised I was a wee bit ambiguous there!!If you have both dip and main on at the same time (some cars/people do this) then you need to work out amp draw for dip as well, doubled for both headlights, then add to main amp draw. I would not recommend this myself, as that would be quite a big draw on the system. In fact, that is a 30A draw!! Not even certain you can get a fuse big enough to deal with that??
James Posted October 19, 2009 Posted October 19, 2009 Sorry I only just noticed you want to uprate to 100W bulbs...100W / 12V = 8.33 ampsTwo of them is 16.66 ampsYou want to choose the next highest fuse.If you want to replace the wiring then this is what you want... as you can see even the basic stuff is enough at 11A.http://www.autoelectricsupplies.co.uk/product/70If you want the right colours... blue/pink, blue/slate and blue/orange, blue/black - buy a couple of metres of each colour (010701 or 010702) - you probably need less than a metre but best to be safe. You will also need some black for ground - a good ground is as important as the supply so you may as well make that common too.For relays you want two of these:http://www.autoelectricsupplies.co.uk/product/173And two of these for plugging in to the bulbs:http://www.autoelectricsupplies.co.uk/product/46
James Posted October 20, 2009 Posted October 20, 2009 I hadn't finished writing this...You'll also want some thicker cable to go from battery to relays, the 25A stuff - make it brown to be correct :)Talking of relays - you want a couple of these sockets: http://www.autoelectricsupplies.co.uk/product/179 - 140301I have seen these secured with p-clips to the bonnet tubes - this is quite neat.For fusing you can do whatever you want really.. http://www.autoelectricsupplies.co.uk/product/299 this would suffice. You will need a couple of 6.3mm female spades for that too.Also some ring terminals if you want to go from the battery or a large spade (you can usually go direct from the alternator to the lights - handy location)Also a pair of proper non-insulated crimpers - they have a red handle.If you fancy a trip over to see me I'd gladly help you do it, I have tons of bits for doing this and proper crimpers... ;)Someone needs to make a kit for this!
99176 Posted October 21, 2009 Author Posted October 21, 2009 I was going to quickly bash in a couple of relays while I have the headlamps out, but I thinnk I'll get all the bits together, print off this thread and do it properly. Thanks for all the advise and links. Just one last thought, I presume my 18ACR alternator will be man enough to run 100w headlamps all night long(no added spotlights or anything).
James Posted October 21, 2009 Posted October 21, 2009 An 18ACR is 45 amps I think - that should easily power everything. I have one and it copes with 510W of lighting plus wipers no problem at all (though on paper that's only just!)
James Posted October 21, 2009 Posted October 21, 2009 Keith - I'll put together a list because I want to do this for my Spitfire. Might be useful for others too.
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