6V Relay on 12V System

I have 6.4 vdc from my OEM Ford stereo to trigger on my DSP. My DSP will power up when the remote turn on sees the 6.4v but it's hit or miss. It is sensitive to ambient temps. For example, the low voltage will not power it on in the early morning for my drive into work but by noon it's working fine. I can easily tap into a nearby 12v switched source but I'd like to use the 6.4v to keep a feature available. I have a Tyco 6v spdt relay that I'm trying to use to provide a 12v output to my DSP but the 6.4v I'm giving it is not energizing the coil. Giving it 12v energized it just fine. Long story short, I'm trying to figure out if I can power this relay with +6.4v on pin 86 and -12v(???) on pin 85? I didn't think the ground really mattered but I honestly don't know. I'm thinking I probably received a 12v relay mislabeled as 6v.

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2011 Ford F-150 Super-Crew FX4
HU: Pioneer AVIC-Z1
Fronts: Infinity Kappa 682.9cf
Rears: Infinity Kappa 682.9cf
Amp: Profile AP1040
Sub: Pioneer TS-SWX251

Your 6v relay should trigger, however, you could just use an NPN transistor to trigger a relay. Base to your factory Ford turn on, collector to fused 12v, emitter to one side of the relay's coil (ground the other side of the coil). Terminal 30 to 12v, 87 to your DSP turn on.

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My ex once told me I have a perfect face for radio.

geepherder wrote:

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Your 6v relay should trigger, however, you could just use an NPN transistor to trigger a relay. Base to your factory Ford turn on, collector to fused 12v, emitter to one side of the relay's coil (ground the other side of the coil). Terminal 30 to 12v, 87 to your DSP turn on.

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An N-channel FET connected on the ground side of the relay coil (other terminal connected to 12V) would be a more robust solution.