![]() ![]() While the rest of the car locks close with authority, our fuel door actuator sat silently. The doors seemed to lock and unlock on cue.īut then we noticed something: Our fuel door wasn’t locking and unlocking. So we checked the rest of the central locking system. We unplugged the actuator and tested the draw. Sometimes it didn’t seem eager to unlock. Our trunk lock actuator had always seemed a bit flakey, though. We couldn’t find any issue with the headlight washers. The interior, glove box and trunk lights all turned off when the car went to sleep. Some internet sleuthing helped narrow it down even further:įuse 49: anti-theft, central locking, interior light, windshield washer system, front windows.įuse 52: central locking, glove compartment light, hand lamp, interior lights, passenger compartment/trunk lighting, windshield washer system.Īfter checking all of the circuits on our list, we circled back to fuses 49 and 52. We started by checking out the easy items on the list of systems tied to those two fuses. Pulling each of these dropped our draw from about 2.7 amps to about 40 milliamps.Īccording to the fuse chart found in the glove box, both of those fuses are associated with the central locking system. We saw some minor variations but nothing that caused alarm–until we got to fuses 49 and 52. Then, one by one, removed each fuse on our list.ĭid the current draw change? If not, we reinserted the fuse and went to the next one. Then we set the multimeter to measure DC current. We disconnected the battery’s negative lead and placed the multimeter between the lead and the battery's negative post. According to Rennie, it’s about 50 milliamps. We could have continued to the test light but small issue: Even when the engine is off and the car is sleeping, the M3 still draws some current. We also cruised the internet for other likely suspects and made a list of fuses often associated with battery drains: 63, 50, 37, 41, 62, 49, 52, 60, 57, 7, 41 and 67. ![]() And our HVAC didn’t display any issues.īut we still noted the fuse that controls the final stage resistor: 50. Plus, for what it's worth, we knew that the previous owner had replaced that part. BimmerWorld has them starting at about $35.īut we’d rather be more methodical instead of just throwing parts at a problem. A popular one: just replace the "hedgehog," also known as the final stage resistor, as it’s a likely culprit. The (all-knowing) internet gave us a few clues. The HVAC wasn't acting up, and our car doesn’t have any aftermarket electronics. Even the trunk and interior lights seemed to behave. When the car was parked and sitting, we didn’t notice any fans running, lights turning on, or the like. One thing we knew: The car wasn’t doing anything weird or obvious. We checked the battery voltage every evening.Īt this point, it was obvious that we had a problem. The car was not plugged in or driven during this test. So we measured the battery’s voltage every day. But how much? The car has some electrical draw when sleeping, right, so did we really have a problem?įirst step: How much was the draw actually hurting us? Then we placed a test light between the negative battery lead and the negative battery terminal. So, we followed Carl's instructions, but added in a step: Rennie from Redline Bimmer Performance told us to allow the car to fall asleep. We also reread a tech piece that he wrote for us about chasing electrical issues. Okay, really, we called Carl Heideman because he knows all. That seemed to keep things in check, but we knew it wasn’t a long-term solution. Our solution for however many years: Just keep the car parked on a CTEK battery tender. But, he added, it wasn't bad enough for the battery to die overnight. In fact, we knew it was a problem when we bought the car because the seller–and old friend–told us. Our E46-chassis BMW M3 had been shedding some electrons–not enough to leave us stranded, but we knew there was an issue. How do many of us deal with electrical issues? Ignore them. ![]()
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