kill switch diagram not working

Passive Starter Kill: 2000 Lexus SC400 [Nakamichi System]

Wired up the passive starter kill relays together and triple checked all wiring and diodes used.

The HEADUNIT keeps cutting the source 12V+ needed to activate the relay setup and start the car.

I tapped into the antenna lead, only for the headunit to cut power to the antenna once the relays are connected. If I disconnect the relays, the antenna resume functioning.

The same happened when I tapped the AMP line of the radio.


What can I do to this relay setup, so that it will not interfere with the headunits overload circuit?

What do you want this passive starter kill to do?

Why can't you run an independent fused 12volt source to the relay system -- is your intention to passively kill the ability to start the car if the stereo is stolen?

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Yes, a passive starter kill. The point of using this setup is for a seamless integration.

A switch with an independent 12V source would be "obvious" as "the" kill switch.

Integration it into the function of the headunit is less obvious, therefore more secure.

There is a couple of options that I can think of that might work, but I am not sure:

1) Diodes across each of the relay coils [ not sure if this will lower resistance]

2) A separate AMP trigger relay with own 12V source and GND. [not sure if this will setoff the overload circuit protection as well]

Any input?

lexelite wrote:

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The HEADUNIT keeps cutting the source 12V+ needed to activate the relay setup and start the car.

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The only lead that should be cut is the starter lead. The relay on the right in the diagram must see 12 volts from an ignition lead on terminal 30 when the key is in the run and start positions. If this lead does not see 12 volts during both of these, the relay on the right will not maintain a latched state.

If you do have 12 volts during both key positions, check that your diode is good and replace if necessary. Once 12 volts is applied to terminal 85 of the right relay while the key is in the run position from the radio, the coil of the right relay should stay energized until 12 volts is no longer present on terminal 30.

If your head unit is having issues only as a result of conencting to the relays in the diagram and the diode is good, let us know and we'll try to go from there.

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the12volt • Support the12volt.com

....so your head unit is cutting off as a result of connecting to the relay on the right through a 1 amp diode? If so, adding yet another relay just to trigger that one will likely not work, but worth a try just to prove one way or the other. Adding diodes across the coil won't hurt anything, but it shouldn't matter either. If there is anything else connected to the power antenna lead of the radio, try adding a relay before everything you wish to control with that output.

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the12volt • Support the12volt.com

the12volt wrote:

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lexelite wrote:

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The HEADUNIT keeps cutting the source 12V+ needed to activate the <A class=orglb title=relays style="COLOR: black" href="https://www.the12volt.com/relays/relays.asp">relay</A> setup and start the car.

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The only lead that should be cut is the starter lead. The relay on the right in the diagram must see 12 volts from an ignition lead on terminal 30 when the key is in the run and start positions. If this lead does not see 12 volts during both of these, the relay on the right will not maintain a latched state.

If you do have 12 volts during both key positions, check that your diode is good and replace if necessary. Once 12 volts is applied to terminal 85 of the right relay while the key is in the run position from the radio, the coil of the right relay should stay energized until 12 volts is no longer present on terminal 30.

If your head unit is having issues only as a result of conencting to the relays in the diagram and the diode is good, let us know and we'll try to go from there.

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Thanks. I will check with directly applying 12V to the source lead in the setup and let me you if the relays setup is allowing ignition.

the12volt wrote:

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....so your head unit is cutting off as a result of connecting to the relay on the right through a 1 amp diode? If so, adding yet another relay just to trigger that one will likely not work, but worth a try just to prove one way or the other. Adding diodes across the coil won't hurt anything, but it shouldn't matter either. If there is anything else connected to the power antenna lead of the radio, try adding a relay before everything you wish to control with that output.

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Just tested with a direct 12V+ lead and the relays were not energized. Will have to test relay setup.

Just to verify:

1) The starter wire was the only wire cut.

2) Ignition wire only applies power at ON or START position. Same wire used to power OBDII Connector Data Link.

3) 1 Amp Diodes were used on both the 12V+ ANT Source [Pin 85,85, 87 Left] and the Key side of Starter [Pin 87 Left].

So what is most likely the point of failure?

Open relay box and both diodes used tested good as well as wiring.

Can only see 2 possible issues:

1) The diagram calls for 2 independent grounds, where I connected both 86 pins to a common ground wire.

2) Used a 1A diode for Pin 87-left on the Key Side of Starter. Starter wire is 12AWG and the diode has a thin strip of metal. Metal might be too thin to properly turn starter. I will eliminate the diode for a direct connection to this pin.

For the last attempt, I will also add a diode across both relay coils.

Any more suggestions?

One ground will be fine, no need for two spearate grounds. I would not add a diode to 87 of the left relay and there is no need to add any other diodes than what I have in the diagram. If you can not get the relays to work as described on the bench, then you have something wrong. If possible, post a picture of the relays/wiring.

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the12volt • Support the12volt.com

1) Bench tested the setup and was able to energize the coils. Eliminated the diode on pin 87 upon install and was able to successful start car with a direct wire of turn on lead.

2) Was able to defeat the overload circuit protection of the headunit by using a separate acc relay with a direct 12+ connection.

3) The last issue of the install seems to be that the pos current from the antenna lead is not a constant 12V+. It floats from 3VDC to 11VDC. Not enough to trigger the ACC relay and start the kill-switch setup.

What can I use to bump the current from 3VDC to 12VDC so the ACC relay coil can properly engergize, thus start the car?

https://www.minute-man.com/acatalog/Philmore_Minature_PCB_Power_Relays.html

This site has minimum 3 volt relays ... perhaps you can mount it to a circuit board, then using a project enclosure (radioshack) and have this 3 volt relay drive an automotive SPDT relay that'll run your whole setup.

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peterubers wrote:

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https://www.minute-man.com/acatalog/Philmore_Minature_PCB_Power_Relays.html

This site has minimum 3 volt relays ... perhaps you can mount it to a circuit board, then using a project enclosure (radioshack) and have this 3 volt relay drive an automotive SPDT relay that'll run your whole setup.

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Thats a great option! I was reviewing the Soundgate, PIE, PAC, and Peripheral Low Voltage Triggers and they seem relatively pricey. Was wondering of the 4 options here for a low voltage trigger, which one(s) is the most reliable?

Any experience?

I have used low voltage relays for other electronic devices... but when I searched for these (after reading your post) I was looking for cost-effective... I used a low-voltage relay that I ordered through radioshack's catalog a year ago for a model airplane... worked like a charm (for that application) (3 volt lighting system from a 14.4vdc recharchable battery system)

For the low cost of these relays in the link, you really can't go wrong .. I would opt for the 3vdc power relay to make sure you always can start your car even if the antenna power wire dips close to 3vdc.  If you went with a 5vdc relay ... the pull-in voltage is 75% of that .. so a little over 3dvc.... so it may drop the 12 volt relaying every once in a while...

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I would also use a variable DC transformer (available pretty much anywhere, wal-mart, radioshack, etc) to test this low-voltage relay and see if the trigger really falls out below 3vdc.

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https://www.discount/detail.aspx?ID=370

$18.00 for 1 volt PIE trigger at this site, already has enclosure and is pre-wired.. may be the better way to go.

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Thanks!

I already used a radioshack project box for the 2 kill-switch relays. Underneath the hood, real-estate is at a premium, so I will be choosing the smallest prewired option.

Of which, the Peripheral LVT can be triggered at 1V as well and costs ~$5 cheaper than the PIE equivalent.

Will choose this option and be complete with the setup as soon as it arrives.

Thanks for all the help guys !! The setup was a PITA, but will be well worth it.