Driving (or, trying to…) a 5sp manual 2001 Honda Civic. It has had some electrical issues in the recent past, currently has a nearly new battery (~3 months old), and a new alternator less than 1 year old. Lately, the battery repeatedly drains overnight or over just a few days. It will start and run fine with a jump, and I just took it on a 3 hours drive and it handled it with no problem, so this pretty definitively rules out the alternator (which is new anyway).
My first suspicion was a parasitic draw, but when I try to measure it, nothing! Here’s what I did: unhooked negative battery terminal, and used a multimeter to measure current from the negative cable to the negative terminal. As far as I can tell, there is NO current being drawn when the car is off (should I be suspicious that it is 0A?). When I first connect the multimeter, it will show ~100mA which quickly goes down to 0mA after a few seconds (even in uA range, it is 0.000…). To make sure the multimeter worked, I turned on a few car lights, the radio, etc. when the meter was connected and the current indeed goes up.
My first thought was a bad battery, but I took it to Walmart to get tested, and it tested fine… Remeasured it after it was charged and tested, and still 0 amps. This made me think that maybe the ground connection is bad, so I tried testing the connection with the meter, but it seems fine (relatively low resistance, meter beeps when touching to ground cable terminal and chasis mount points).
I’m kind of at a loss here… not the alternator, not the battery (assuming a Walmart test is definitive), but no draw of any kind when the car is off. However, there is no current measured at uA scale when stopped… which is weird to me. Any thoughts?