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Wiring for Hidden Security Switch/Relay

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Forum Name: Car Security and Convenience
Forum Discription: Car Alarms, Keyless Entries, Remote Starters, Immobilizer Bypasses, Sensors, Door Locks, Window Modules, Heated Mirrors, Heated Seats, etc.
Printed Date: December 01, 2021 at 4:04 AM

Topic: Wiring for Hidden Security Switch/Relay

Posted By: ernesto0o
Subject: Wiring for Hidden Security Switch/Relay
Date Posted: January 15, 2019 at 12:16 PM


In the past two months, my wife's car was almost stolen twice by most likely the same person. I'm planning on wiring a hidden relay that will use possibly the wiper blade switch and the high beam switch. My end goal is I'd like to be able to turn the key to the on position, hold the key in place, and in order for the car to start, I'd need to press the high beam and the wiper blades button at the same time.

What type of relay will I need for this type of configuration? Single pole double throw, double pole double throw, or something else? For security reasons, I'd rather not say what type of car it is.

I'm using the ignition power wire to connect to this circuit. If you need more information or any better ideas than this, I'm certainty open to it.

Thanks in advance,



Posted By: geepherder
Date Posted: January 15, 2019 at 2:27 PM
Try this:


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

Posted By: ernesto0o
Date Posted: January 15, 2019 at 5:09 PM
That's great. Thanks!

Posted By: Custom_Jim
Date Posted: January 16, 2019 at 12:47 PM
Without vehicle information, just check to make sure you are getting the proper signals from the headlight switch and wiper switch (switches can connect power or ground) and then also verify that something like the output from the wiper switch does not go dead while cranking as some vehicle electrical designs do not allow the wipers to work so more power can be available to crank over the engine.


1968 Chevy II Nova Garage Find 2012
1973 Nova Custom
1974 Spirit of America Nova
1973 Nova Pro-Street
1977 Nova (Sold)

Posted By: davep.
Date Posted: January 16, 2019 at 11:27 PM
I've done a bunch of these ghost switch systems. They're fun to sketch up and then work the sketch for bugs and unintended operation, correcting errors as you go. I began with the "horn activated starter interrupt" in the Relay Section of this site about 8 years ago. I've expanded and improved my systems continuously, with about 15 installations in my or friends cars. No two systems have been exactly alike. It's fun, but a strong understanding of relay-relay logic and automotive electrical systems is very helpful.

Geepherder's diagram is simple and workable, but there are some drawbacks:
A: The high beams and wipers will operate when you use them to actuate the ghost switch thus giving away the "what needs to be done" to start it.
B: I like to use latches to keep the system active until a door is opened. I can stop the engine to order my burger and restart without doing all the "stuff" again. Also helps with service work. Leave the window open and reach in to start/stop the engine during service.
C: If you have a Remote Starter, you have to incorporate a bypass to activate the ghost switch with the Status from the R/S.
D: You should have a hidden bypass switch in case of malfunction. Or use N/C relay contacts, and a switch (or a fuse in the stock panel, my favorite) that removes power to the array which defeats it as a bypass.

It can get complicated in a hurry. The system in my Super Duty has 12 relays. It interrupts both Starter and ECM power. (I know, we're not supposed to interrupt ECM. But the ford starter solenoid is right on the fender. Too easy to jump). It requires two actions to defeat. It has bypasses for the R/Starter. It remains powered up for the 10 minute duration of the DAB. And the last line of defense is an interface with the GWA on the Viper so that if they DO figure out the required action, it STILL won't start if they don't have a fob to disarm the Viper, or can't find the button for the disarm.

Sorry for the TLDR. My point is that there's quite a bit to a well thought out system. Geepherder's deal will accomplish what you've asked for, and I commend him for taking the time to create and post the diagram, but it's almost too elementary.

Posted By: iskidoo
Date Posted: January 17, 2019 at 1:13 PM
How are they getting that far to begin with? Shouldn’t an alarm be sounding when they first try to enter the vehicle? If it’s a vehicle like a convertible or has open access, is there some kind of perimeter sensors you can setup in the cabin that will trigger an alarm?

Another idea would to be consider a proximity type unit in conjunction with some ignition or starter kill relays so that when she got near the vehicle with the fob in her pocket, everything would startup like normal.

Steve G

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