buzzkilldude
08-21-2024, 09:03 AM
My a4 I've had for 5 years now has been benched for the past few months due to a voltage problem I just can't solve. The new battery reads 12.5v as it should with close to full charge, but only reads 12.1v at idle. I replaced the alternator with an OEM new one as well, previously the battery read 10.96v at idle, so it did something, just not enough. I know it should be reading 13.5-14v. OBDII shows a "system voltage low" error but nothing else.
I then tested for voltage drop, and when the engine is idle I got a 2.14 voltage drop between the positive battery terminal to the alternator b terminal. I get no voltage drop from ground to alternator case, however.
What parts of the circuit should I be checking, is there a diagram somewhere for the fuses that connect the positive battery cable to the alternator that I can test? I can't follow where the alternator cable goes since it seems to go under the engine block. Any insight would be helpful, thank you
I then tested for voltage drop, and when the engine is idle I got a 2.14 voltage drop between the positive battery terminal to the alternator b terminal. I get no voltage drop from ground to alternator case, however.
What parts of the circuit should I be checking, is there a diagram somewhere for the fuses that connect the positive battery cable to the alternator that I can test? I can't follow where the alternator cable goes since it seems to go under the engine block. Any insight would be helpful, thank you