I agree, 30 days at 75mA is 54 amp-hours, enough to kill many batteries.Doug,,, thank you for calculation,, yes i calculated the same rate of battery discharge,, over a month. Problem is compounded by fact car is only driven 2 miles twice a day,,,, the battery seems to lose 50% of its charge after 2 weeks ??? Battery was tested and replaced twice,, no change.
Alternator does charge at proper voltage (over [email protected]) and does charge-up battery when driven more miles. Never had this problem before with low battery!!!
Thinking further,,,, maybe i'm getting additional battery drain from (defective) alternator too ??
,,,,would a leaky diode still charge battery normally ??
but i still have 75ma constant drain on the BCM fused circuit 1.8A/dayX30=54amps/month !!!!!
and car wont start with very low battery,,, may actually be fewer days than calculated.
Had the car in shop,,, mechanic did verify, but could not identify problem causing low battery,, maybe electrical not his specialty ??? ,,, told me hes been working on cars for 25 years
I think you're on the right track with the BCM fuse. The remaining challenge is to narrow it down from there.
As for "electrical not [being] his specialty", my observation is that, for many, electricity is black magic Civil engineers think electrical engineers are spooks. And electrical engineers think RF guys are spooks Throw in some encryption, and it gets really scary
Seriously, I was never comfortable with it until I got some rigorous schooling in college. Prior to that, everything was a hodge-podge of fuzzy terms - AC, DC, rms, peak, average, continuous, balanced, unbalanced, etc.
So it's understandable that your guy may not be real comfortable with it.
Back to diagnosing the parasitic draw, the challenge at this point is that it becomes tedious. With each test - each removal of a load by pulling a downstream fuse or removing a bulb - the quiescent 75mA load may jump to a different level, either higher or lower. Before you can move to the next text, you will need to re-establish the 75mA draw, which may take a few steps and several minutes of waiting. So it can take a while to narrow it down to the source.
Of course, if you see the 75mA draw drop way down when you remove a load, then you may have found the problem. So perform that test again to confirm it, then shout "eureka!"
In short, it can be a grind going thru this looking for the culprit. Some of the hi-end test equipment at the dealer may be helpful. For example, it may be able to communicate with the BCM to find out what's keeping it from dropping to its lowest current draw - ie, going into standby. Most ordinary scanners won't be able to do that. So you're left with disconnecting cables, bulbs, etc, until that 75mA goes away.
That said, I think you're pretty close to finding it. So I encourage you to keep looking.