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Old 01-10-2011, 12:52 AM   #1
JerrysTruck
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12 volt relay question

May be a dum question. But MAD (madelectrical.com) Said that with older cars its better to install a dual relay on the headlights to make them brighter then normal. Because of the drop in volts. Like nearly 14%. I believe relays will help. But with that said,why stop there. If it makes the headlights brighter with the drop in volts. Why not install realys on the tail/brake lights to have brighter brake lights on older cars and maybe even on the wire going to the distributor. Wont they have a better out put with relays installed. Or am I thinking wrong ? Anyone done this ? Seems like the 14% volt drop should be throughout the car,if it is to the headlights. The guys that install aftermarket power windows in old hot rods will have more powerful power windows I guess to with relays also.
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Old 01-10-2011, 12:04 PM   #2
red71cheyenne
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Re: 12 volt relay question

It makes sense to do it, it just depends on if the work is worth the result. For headlights, its a pretty easy upgrade and fairly standard wiring. The rest of them you run into the issue of where to put the relays, where do you get them, how much do they cost and on and on. I think the easiest way would be to get a fuse block/relay block out of a newer vehicle and then adapt it to your application. But then you run into the problem of how good is the original wiring and how hard is it to adapt. Anything you can put on a relay is going to operate better because it will be getting full B+ voltage, but getting there may not be the easiest feat.
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Old 01-10-2011, 12:51 PM   #3
kieth
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Re: 12 volt relay question

relays are for high amperage draw situatuons, the headlights are a hi amp draw circuit, the running lights are not. You might put LEDs in place of the bulbs in your turn signals, running light, etc would reduce the overall amperage draw and be brighter. money better spent that putting relays on a 2 amp circuit. Kieth
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Old 01-10-2011, 01:08 PM   #4
fixit-p
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Re: 12 volt relay question

The taillights will only draw about 1 amp total for ~ 1.5% voltage drop and the brake lights are wired independently so 1 bulb will draw ~ 2.1 amps for ~ a 3% voltage drop. Imo both are within acceptable range and not worth running a heavy gauge wire to supply the 3 relays at the back of the vehicle.
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Old 01-10-2011, 04:39 PM   #5
JerrysTruck
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Re: 12 volt relay question

Ok, Thanks guys !
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Old 01-10-2011, 08:20 PM   #6
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Re: 12 volt relay question

Agreed, the headlights draw quite a bit more then the tail lamps. As far as ignition, GM usually used a 12g wire for it that will handle the coil's current just fine.
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