Audi Repair Questions? Ask a Mechanic for Answers ASAP
Hello, my name is Bobby. Thank you for the question. Typically this occurs because of a failure within the positive battery cable. The issue is typically in the section of the wire that connects to the large post on the alternator. This wire develops high resistance and this occurs. I would either do a resistance test of this or if you have a voltage meter you can check the end at the alternator and the end at the starter and see if the voltage drops off. If the voltage is higher at the alternator than at the battery then the wire is bad. If not then you are not getting an on signal from the PCM which may be failing.
What is the output voltage of the alternator?
Does the violet/blue wire have battery voltage when the key is turned on?
If the battery is not charging and there is no light then your battery module, located on the battery may be failing. The system will also only charge when it thinks it needs it. You need to see if this wire has voltage. If it does not then the monitor may have failed.
I would need to know what the voltage is at that wire at the alternator. I would then need to know what the voltage is at that same wire at the little box on the battery. Also see what the large red wire at that box reads.
Yes, you can come back anytime with that information. Yes, that is the box I am talking about. Do the test on the 20V DC scale.
What size battery is in the car?
Ouch. I thought it was in the harness but from the tests you did and the results you gave me it sounded like it was ok. Hopefully it will be worry free after this.