I help an elderly woman maintain her 2011 GLK350 4matic. Beginning just days ago, the car drains a fully charged battery to the point of being unable to turn over the engine in 90-120 minutes.

The battery is five and a half years old, but when fully charged still passes CCA and CA tests, and holds its charge when disconnected from the car, so I'm not concerned with it.

I replaced the alternator last summer to correct a low output voltage and AC wave issue and it's performing perfectly.

Using a clamp meter I measured a 0.9 amp steady draw on the battery. I closed both hood and the rear hatch latches and let the car go to sleep, then performed a parasitic draw test on both fuse panels. I had a few inconsistent results that seemed to come and go, so I wired up a sealed beam lamp and connected it between the negative post of the battery and the cable. After allowing the car to go back to sleep again, the lamp suddenly illuminated at full brightness and remained lit for about 3 to 4 minutes, then faded out. This behavior repeats about every 4 minutes. At some point I noticed that when the lamp illuminates, I heard a relay clicking from the front fuse panel, and I believe I narrowed it down to relay N10/1kN.

(Interesting aside: the relay does not open when the lamp fades out - it remains closed until the moment right before the lamp lights up again, so there's actually a very quick double click when the lamp illuminates. When the lamp is illuminated the amp clamp measures over 4 amps of steady draw, and drops to 0.9 amps as the lamp fades out.)

My thought is that the relay closing while the car should be asleep is a symptom of a bad SAM, but I'm open to suggestions and prior experience, especially seeing as I'm finding it difficult to source a new SAM for this particular car.