The relay measures ambient temperature to control the time the light operates. There is an electrolytic capacitor in the relay that affects what this time is. If that capacitor is leaky, your light time will drop. The relay should keep running for 30-90 seconds, although the current draw decays exponentially.

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'82 300SD - 361K mi - "Blue"

"Good judgement comes from experience. Experience comes from bad judgement."

listen, look, .........and duck.