miata underhood +12 volt

I'm looking to install a lc-1 on my 91 miata running mspnp tomorrow. I am planning to run the main power line to the alternator with a 5 amp fuse inline, ground to the block where I ran a fresh ecu ground to. My specific question is where to hook the turn on lead. From what I understand it needs to be a source that has +12 volts while cranking. Instead of prodding around with a meter, I imagine someone on here already knows a good source to tap. Thanks in advance.

I've run electronic hourmeters off of the ignition coil (+), but I'd imagine that might be too noisy for the finicky Innovate stuff.

If the car doesn't have ABS, there's a hot connector where the fuse would go in the box under the hood.

Never mind, I just realized that's b+ - at least, I'm pretty sure it is. You need switched. is the blue connector by the drivers headlight hot while cranking?

Miata headlights shut off during cranking. Maybe the wire to the relay that controls the lights-off-during-cranking function?

I don't think there's anywhere on the car that gets regulated 12v during cranking with the possible exception of the factory ECU power input. You'll get switched B+ from the starter solenoid wire during cranking - will that do.

For my LC-1, I bought a O2 sensor pigtail from FM salvage and used the power/ground connectors from that. I didn't have great results (the contraption stopped working right), so you might ask the smarter folks around here if that wire can provide the current necessary to run the LC-1, but that was the solution I came up with. Also provides an easy way to send the WBO2 sensor signal back towards the cockpit (if your wiring harness at the CPU is so arranged)

The logic for circuits that lose power during cranking is in the ignition switch, not a relay. I'll check a diagram at work tomorrow.

Tell me about why the lc-1 needs 12v while cranking? It's not reading anything at that point, it's still in warm up mode.

I'm pretty sure i just powered mine off the cig lighter circuit. It doesn't take much power at all. I really don't think it matters if it's interrupted in cranking. Mine is.

Keith wrote: You need switched. is the blue connector by the drivers headlight hot while cranking?

The blue plug is hot anytime that the ignition is on.

On a related note, I want to install under the hood for ease of connections and what not. Is this something that should be inside the cabin? If so, where is a good place to get the O2 sensor and wire through the body?

bigbrainonbrad wrote: On a related note, I want to install under the hood for ease of connections and what not. Is this something that should be inside the cabin? If so, where is a good place to get the O2 sensor and wire through the body?

The controller is made to stay under the hood. It's fine.

Did you ever find a wire to tap for +12v while cranking? I'm working on the wiring for my MTX-L and would like to have it on while cranking so it is working after it starts rather than taking 20-30seconds to start reading.