# I need a relay or something



## zogthegreat (Sep 15, 2016)

Hi everyone!

I have a bike rack on my 2011 Ford Taurus that I want to install a light that activates when I step on the brakes. Due to the way Ford setup the lights on the Taurus, I can't just tap into the brake lights in the rear. I did manage to tap into the brake light that is in the back window, but due to voltage drop, I'm only getting 6v at the end of the wire. Since I already have a 12v hot wire running to my trailer wiring, what I would like to do is have the wire that comes from the rear window brake light run to some kind of relay or switch to the 12v hot and then from the 12v hot to the bike rack.

Does anyone have any suggestions?

Thanks!

zog


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## jacampb2 (Dec 3, 2010)

If you have trailer wiring then why not use the brake light wire from that harness? I'm guessing that your lights are LED and are PWM'ed and that is why you are getting six volts. You should definitely NOT have that kind of voltage drop across a simple wire unless you are using recycled coat hangers for wire.

You can do exactly what you are describing, but you will want a quality relay rated for a lot of contact cycles, it is probably going to cycle dozens if not hundreds of times every day...

There are much easier ways to accomplish what you want-- first and foremost would be to use your trailer wiring harness, especially since you were wanting to tap into it anyhow for 12V.

Good luck,
Jason


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## Sine Swept (Sep 3, 2010)

Solid state relay, no moving parts.


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## jacampb2 (Dec 3, 2010)

Yes, that would be better than a mechanical relay, but many of the common SSRs out there are meant to switch AC loads. There are DC SSRs, but my experience is that many of the ones listed on eBay and such are the thyristor based variety and will not switch DC. He could also quite easily google how to use a mosfet as a relay and get a plethora of ideas on a simple circuit. 

My assumption is that if he is asking this question about a relay, that he probably lacks the skills to assemble something on his own.

I think the simplest solution is still to use the trailer wiring...


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