Hi,
My 91 BMW 318i has an issue with its service interval computer, that caused my tach and MPG meter to stop working. Ill be fixing it soon, but it prompted me to look a bit more into the electrical system.
I checked voltage at the battery, and with the key off, had 12.39V, and with it on, 12.13V. This is a bit too low, right? I know it is charging properly, as with the car on, I get 13.68V.
The strange thing is that at a number of fuses, I got 1.04 V (and when I checked them again today, noted that I had 0.55V at them). I thought this was a potential issue, but did a parasitic load test and found that it is not an issue that these voltages are liek that. All the same, why would I have a very low voltage at a few circuits, which then go to the proper 12.xxV when the car is on?
OK, now, parasitics... how much parasitic load is considered normal?
I found that my car has 50.4 mA parasitic load w/ trunk light disconnected, and everything off (the battery is in the trunk, thus why I had to disconnect that light). I found the following:
-Amp draw @ battery = 50.4 mA
-Remove fuse 4,5,6 and 12 (these fuses were the ones where I saw the 1.04 or 0.55V) = 50.4 mA
-Remove fuse 10, 21 only = 13.3 mA
-Remove fuse 10 only = 50.4 mA
-Amp draw for keyless entry (atached directly to battery) = 8.7 mA
So, the stuff on circuit 21, which includes the glove box light, flashlight (dont have), key and seatbelt warnings (only ignition key one works), interior lights (only have the two above the rear doors), radio memory, luggage compartment light (disconnected for test), active check control (dont have), SI, OBC (dont have), fuel delivery, tach/fuel economy gauge, digital clock (dont have), Multi function clock.
So it seems that between the multi-function clock and the radio memory (and whatever else on fuse 21 might have a memory, etc), I pull 37.1 mA. Is this high? The whole rest of the car only pulls 4.6 mA (considering the keyless takes 8.7), which isnt bad.
I should extend to say that in the last 4 months, my car has sat 4 times for a month at a time, and the battery was A-OK when I returned, and the car started, so this draw seems OK - but is it high, normal or low in the big scheme of auto operation?
Any comments, ideas or suggestions???
Thanks again for all the help,
JMH