Rocker Switch That Only Works When Vehicle Is Unlocked

Hello everyone, this is my first post here. Apologies if this is not the correct forum, this is the closest I could find since it will be based off using a viper alarm.

I plan on adding a momentary press 3-way rocker switch to the outside of my Tailgate of my 86 4runner that rolls the tailgate window up and down. The wiring for the switch is already there. One wire is for power window up, the other is for power window down. When you press the switch up or down it will complete the ground for one or the other to roll the window up or down.

What I would like to do is create a break in the circuit before the ground, which is opened or closed based on if the viper alarm is locked or unlocked. I'd like to make it so if the alarm is armed the circuit is open and the rocker switch will not be functional, and if it's unarmed the circuit will be closed and the rocker switch will function.

In the photo I've added a red dot where I would like to make a break in the circuit. I'm unsure if this needs to be done with a relay, or if a switch that stays open or stays closed from the alarm trigger is possible.

Thanks!

Does the switch control the motor directly, or control relays/module? How much current flows on the ground wire when the motor is operating? Gauge of wiring on switch might help give an estimate.

They're just trigger wires for a relay that operates the power window. I would actually be using the stock wiring for the stock key switch that's on the tail gate, but in place of the key switch I would be using a rocker switcher. Wiring the rocker switch is no problem for me, it's being able to enable/disable the switch from the viper alarm being armed/unarmed that I'm having a hard time wrapping my head around.

There is an alternative workaround I've thought of too. I suppose I could also tap into one of my door lock detection switches so the ground for the locker switch has to pass through the detection switch in order to complete the ground. If the door is locked then the rocker switch won't have a ground.

Interesting question. I'm thinking there is an easy way to do this but I'm drawing a blank right now.

The main issue is creating a circuit that will not deplete the battery. Using the Vipers GWR sisgnal comes to mind as it's present when the system is locked and armed but keeping a relay energized all the time the alarm is armed to prevent the ground from getting to the window rocker switch will kill the battery. Using GWA in reverse and only energizing the relay when GWA is not present will kill the battery if you fail to lock and arm the Viper.

Here is one possible way to do it...

How about a circuit that will only allow the window rocker switch to function for a fixed period of time after a Viper unlock command?

There are +12V Relay Timer PCB's available on EBay for about $5. You could set it up so that when it sees an Unlock command from the Viper, it will energize its' relay for a fixed period of time ( some show a max of 16 minutes ). During this time period the ground signal is allowed through the relay and to your window switch. Need more time? - press Unlock again.   The relay would only be energized for short periods of time when a user with the Viper remote allowed and not have a major impact on your vehicle battery.   Quiescent current draw is about 12mA and goes to 50mA when the relay is energized.

Search EBay with "12V LED Display Delay Relay" to see and read info on these circuit boards.

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Soldering is fun!

There are lots of ways to "skin the cat"...another way to do this is to use a latching dual coil relay.   Look for Potter & Brumfield KUL-5D15D-12. This is a 12V latching relay with separate set & reset (latch & unlatch) coils. Search "KUL-5D15D-12" on ebay to get a look at one. These tend to be pricey, but you can find them between $20 and $30 if you look around.

The contacts are rated for 10A, and are in a "form C" configuration, so there is a common, normally closed to common and normally open to common. A lock pulse will open the relay, preventing the switch from operating; an unlock pulse will close the relay, allowing the switch to operate.

The relay's latch (lock) function will keep the relay contacts open until the next reset(unlock) pulse--no battery drain. Coils draw about 130 mA during the pulse.

Here is the part pin/wiring layout:



The way you would wire this up is:

Terminals 8 & B to fused +12V constant

cut wire at red dot (your drawing)

Terminal 7 to Ground (one side of cut wire)
Terminal 2 to Switch pin 1 (other side of cut wire)
Terminal 5 left unconnected

Pin 9 to unlock (or an Aux linked to unlock) from Viper

Pin Pin A to lock (or an Aux liked to lock) from Viper.

I'm sure there are other latching relay options out there, but this is one I've used in the past with success.

Good luck, I hope this helps.

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Lectric Guy

Thanks for the replies! I like both of those ideas.

I think I'd be leaning more towards the matching relay.

Regarding that latching relay, does it also allow for the ability to latch and unlatch off of the same momentary signal? Or does it need 2 different signals for on/off? There is another project I've had in mind on my 4runner as well where I need to make a momentary press switch provide constant power to my rear window defrost, and turn off the power using the same momentary press switch.

Thanks!

For a defrost control, it would make more sense to use the 12V relay timer that Kreg described above. It would turn on the defrost for up to 16 minutes, similar to the timer in most vehicle defrost circuits.


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Lectric Guy

I'd go with the latching relay. The piece lectricguy referenced will add 130mA of load to the lock/unlock circuits of the viper. Don't recall the maximum available on those wires (200mA perhaps). But there are other dual coil latching relays available. That's why I was asking about the amount of current flowing in that portion of the power window circuit. Choose a 12 volt relay that has at least twice the contact rating as the current needed, then look at the coil resistance. Use ohm's law to determine current drawn. Should be able to find a piece with lower current draw.

I figured out how to do it with two relays per direction. You shouldn't need to lock out "up", only "down". So put the following in the down direction:

Relay #1
86 & 30 = Hot at all times
85 = to switch for "down". Also to Relay #2 30
87 = Relay #2 86

Relay #2
86 = Relay #1 87
85 = Viper GWA (orange 500ma)
30 = To switch for "down" Also to Relay #1 85
87a = To relay control for "down".

Cut the window "down" wire. Switch side to Relay #1 85, and relay #2 30. Motor relay control side to Relay #2 87a.
Relay #1 inverts the switch (-) trigger to a (+) trigger.
Relay #2 will open the control circuit if GWA is grounded.
If GWA is not set, the switch (-) trigger is passed to the motor control relay through Relay #2 N.C. contacts.

Sketch it out. It should work. No relays are energized at any time unless the external "down" switch is activated.