looking for a "Hot" circut after the car has started

Koenigturbo

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Oct 4, 2006
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Does anyone which circut stays constant hot, 12 volts only after the car has started and off when the key is off??:3d_frown:
 
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Justin

Speakers?
Mar 31, 2005
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What are you trying to power?

What you're looking for can be found in the ignition harness in the steering column, the cig. lighter, the radio, several places....
 

Koenigturbo

Active Member
Oct 4, 2006
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Justin;1240865 said:
What are you trying to power?

What you're looking for can be found in the ignition harness in the steering column, the cig. lighter, the radio, several places....

Yep, your right,except everything you listed can be turned on before the car has started, it has to after the car started
 

jdub

Official SM Expert: Motor Oil, Lubricants & Fil
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Feb 10, 2006
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Well the FP relay is not powered until the STA signal is active...it is powered during start though. You could use the FP wire from the ECU to the FP relay to activate another relay (connected to battery or IGN power) to do what you want. The yellow wire (mid right side) in this pic:

Main_046.gif



What are you trying to power that needs to have the engine running 1st?
 

hvyman

Dang Dude! No Way Man.
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Apr 17, 2007
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does the cruise control get 12v? im assuming it does. you could wire it into that and switch it on/off when you want.
 

jdub

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tissimo;1240997 said:
If you do this Make sure you have the 12v mod done @ the fuel pump relay so your relay wont be tripping the fuel pump resistor on.

Not necessary. If you tap into the wire pre-FP relay, it will simply actuate both relays at the same time. The ECU FP wire's sole purpose is to actuate the FP relay...it does not provide power directly to the pump.

Actually, after looking at the diagram a bit closer, there will be a problem when the ECU commands the full 12V to the pump under load. The ECU FP removes current and the FP relay defaults to the 12V position. All FP does is switch the pump from 9V to 12v when the ECU detects the motor is under load. It would remove power to the new relay actuation terminal, cutting power to whatever kong wants to power.

A better choice to tap is FC...the green wire to the circuit opening relay in the above diagram. It is powered whenever the engine is running.
 

jetjock

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Jul 11, 2005
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Redacted per Title 18 USC Section 798
Someone has spent too much time exposed to French engineering ;)

While that'd work it's bad practice to connect something (it'd be nice to know what for several reasons) to the ECU bus, especially critical circuits like fuel and ignition. Not that it can't be done, just that one should consider the impact on reliability and the chance of interference. Plus one has to consider how incompetently most owner installed electrical work is done. There are lots of other places where switched power is available that won't stop the car dead should something go wrong...
 

jdub

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LOL...yes I have...as they say: "All the engineers in hell are French" ;)
That point is very valid...loose the FC signal to the circuit opening relay and the car stops dead in it's tracks.