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Automotive Latching Relay

Status: Units are built to order - Please expect up to 2-week delay after receipt of order until order is shipped

Example Applications

For sale here is a compact solid-state 12V latching relay. A "latching relay" is one which switches the output between "on" and "off" when triggered. Each time a new trigger is seen (a "rising edge"), the output changes between on and off. The output stays in its new state indefinitely, or until a new trigger is seen. It is useful for many applications, especially where you would like to use a pushbutton to turn something on and off. You can also use it to switch between two different devices by adding a secondary 5-pin relay.


  • Can be triggered by positive or negative (ground) signal, selected by polarity switch
  • Dual isolated inputs
  • Simple 0.25" spade connectors
  • Solid-state operation for high reliability
  • Compact size: 2.375" x 1.61" x 0.81" (60 x 41 x 21 mm), or
    1.53" x 1.61" x 0.81" (39 x 41 x 21 mm) without the mounting ears
  • 10A maximum continuous load, 20A peak
  • 4.5mA standby current consumption (3mA for LR-N)

Product photos coming soon

This relay comes in a small plastic box with two mounting holes, and 5 standard spade connectors on the bottom. The electronics inside are encapsulated, or potted, in epoxy and are water resistant. The five connections are:

  • +12V from battery (an inline fuse is required)
  • Ground
  • Load - to be connected to the positive connection of device if using positive-switching LR-P, or to the ground connection of the device to be switched if using negative-switching LR-N.
  • 1 & 2 - trigger inputs, to be connected to signals used for switching relay on and off

There are two versions of every LR model: the LR-P and the LR-N. The positive-switching version, the LR-P, switches the high side, or positive side. The negative-switching version, the LR-N only switches the low side, meaning it switches the ground connection of the device, while the positive connection stays connected to battery voltage. Some applications cannot use the positive-switching scheme, so the LR-N exists for customers who need negative-side switching. Most customers choose the positive-switching version.

Note that these relays are NOT fully waterproof. Because the connectors are standard spade terminals, which are exposed to the elements, too much water will cause them to short out; this is only preventable by using waterproof connectors. So be sure to mount these relays in a place where they will not get too wet, or be submerged. High up in the engine compartment, with the connectors pointing down and the back of the relay against sheetmetal, is generally safe, but if you wash your engine, be sure to disconnect the battery power and allow everything to dry before reconnecting the battery.

A packet of 5 matching terminals is included with each relay.

Latching Timing Diagram
Latching Relay Timing Diagram
Latching Relay Connections
Latching Relay Connections
Latching Relay Connections
Latching Relay Connections
Connections photo coming soon

Triggering vs. Switching
One confusing issue with these relays is positive vs. negative switching and triggering. While these relays can use both positive AND negative triggering, they can only do positive OR negative switching: you must order the correct kind for your application. For the purposes of this write-up, "triggering" and "switching" are two different things.

"Triggering" is how the relay is activated, or triggered. When the relay receives a trigger signal on one of its two trigger inputs, it turns on after the time-delay. This trigger signal can either be positive, meaning a +12V signal, or negative, meaning a ground signal. The ability for the LR to recognize either type of signal is useful because some applications need triggering from a switched +12V signal, while others (including many mechanical switches) require triggering from a switched ground signal.

"Switching" refers to how the relay switches power to whatever device is connected to it. The positive-switching LR-P switches the positive side of a device, supplying +12V, while the ground connection is always connected to ground. The negative-switching LR, on the other hand, switches the ground side of a device, so +12V power must be always connected to it, and the LR switches the ground side on and off.

While it would be nice if the LR could do both positive and negative switching, it's not technically feasible, so there are positive and negative versions. Please be sure to order the correct kind after reading through the instructions and examples here.

The price for either the positive-switching Latching Relay (LR-P) or negative-switching LR-N is $32, plus any applicable shipping charges. When you purchase using the PayPal checkout, it will calculate your shipping cost and should give you multiple options for shipping.

Interested? You can order one or a pair quickly and easily by clicking on one of the buttons below. Feel free to add more products to your cart before checking out, and save with combined shipping. If you would like to pay by money order, or have some other special needs, just email us and let us know how we can help you.

Other Information

  • Troubleshooting Instructions

  • Item Added!
    Positive-Switching Latching Relay (LR-P)
    Price: $32
    Item Added!
    Negative-Switching Latching Relay (LR-N)
    Price: $32