Re: Where should I take power for additional rear lights?
Depends on the wattage of the extra lamps you want to add. Every 12W adds 1 amp to the current drawn, so if your extra lamps had (for example) two bulbs marked 12V/24W, then you would need another 4 amps to run the two extra bulbs. If you connect into the live feed to your existing rear lamp, and connect the wire for your additional lights to that, then there will be an extra 4 amps flowing through the feed. That may or may not be a problem, dependent on the size of the feed cable, but if your new lamps are not heavily rated, then connecting into the rear lamp feed is the easiest way. Carrying too much current on a feed wire has two effects:
1. If the current is too high, the wire will get hotter, and if way too high, could overheat, melt the insulation, and short out. That would be a BIG overload though, as most cables are over rated, to avoid the problems in (2). The fuse might blow too.
2, Voltage drop: you only have 12V to play with, and as Mr Ohm's law says, Voltage across a resistor + Current x resistance.
Your wire has resistance, and if you increase the current, then the voltage 'lost' along the length of the cable will increase. So, you put more lights on to one cable, then you end up with more lights, but all of them will be a bit dimmer, because the voltage at the lamps will be lower than it was before. This is why LED lamps are so popular. They give a very bright light, but draw a very small current.
If your add-on lights are LED type, then you should be able to connect into the live ffed to the existing rear lamp without a problem. if your add ons have filament bulbs, and the total wattage of the additional bulbs is significantly higher than that of your stock tail lamp, then you will overload the feed wire. You could convert filament bulbs to LEDs, to reduce the current drawn:
http://www.norbsa02.freeuk.com/goffyleds.htm
For safety, and if you do have a relatively heavy wattage on your new lamps, then you can use a relay to feed the new lamps. You'll get one out of Halfords or local auto electrical shop. Make sure you tell them you want a switched realy, to run some auxilliary lamps, and pick one that has the right amp rating for what you want to do. Take the total wattage of your additional bulbs, and divide by 12, to get the amps needed. So, if your new bulbs have a total rating of48W (as above) then they will draw 4 amps, and you will need a relay rated at no less than 4A. Normally they start at about 6 or 10 amps.
http://www.maplin.co.uk/searchpages/12V_AUTOMOTIVE_RELAY.htm
Take feed from suitable unswitched and fused supply (as described by Gray) to live feed on relay, and take a new wire from relay output to new lamps. Take a wire from the existing tail lamp feed wire to the switch terminal on the relay. When your rear light is on, it closes the switch on the relay, and takes the power to your new lights, and your tail lamp wire is only loaded with the switch current, which is next to nothing.
. I brought them second hand off ebay. Anybody know if there are any spare plug-in points for lights on the Glide? Where would the safest place be to take a live feed otherwise? Thanks in anticipation, Andy.
