Has anyone ever had a problem with this unit draining your battery overnight? I recently bought a refurbished one to replace my original 1692, and since then, the battery has been dead every morning I go to start the car. I took it out yesterday to test my theory, sure enough, I had full battery this morning. Any thoughts?

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1996 E300 D
1992 300D
1990 Ford E-350 7.3 Diesel AKA "the Deep Fryer"