This is the Bueler BU509TD time delay OFF relay. A 12 volt, 20/30 amp SPDT (single pole, dual throw) relay with a built-in adjustable timer.

Delay OFF means the circuit stays live for a set period after the trigger disappears, adjustable from 2 seconds up to 3 minutes. Useful for interior lights, cooling fans, parking sensors and anything that should linger rather than cut out instantly.

This is the third generation, redesigned around what installers asked for: a top-access adjuster you can reach once it's mounted, a waterproof body, and a 340 degree potentiometer for finer control.

The 1 volt trigger is the interesting part. At a 1 volt (1k ohm) threshold it will trigger from sources a normal relay ignores, including detecting an LED turning on, and it's a common fix for amplifier pop.

Specifications

• 12 volt DC, operating range 8 to 15 volts
• 20 amp / 30 amp rated contacts
• SPDT, single pole dual throw
• Delay OFF, adjustable 2 seconds to 3 minutes
• Low 1 volt (1k ohm) trigger
• Internal green LED indicator
• Waterproof, standard automotive relay format

Need the circuit to switch on late rather than off late? That's the BU510TD delay ON.