A6 4.2 Vier

I have been having battery related problems recently. The first problem was that the positive battery post under the hood was getting very hot while the engine was running to the point it would create a blister if a finger was left touching it for more then a few seconds. I suggest that those with older A6 model cars check for this problem.
Here is the Link for the resolution of that problem.

The battery was still draining after solving the hot alternator cable so I decided to replace the 5 year old non-AGM "Audi" battery with a new H8 AGM Interstate battery from Costo for under $200.
The Interstate website directed me to purchase an incorrect Interstate battery, I stuck with my gut and purchased the H8 battery and ignored what the website told me to purchase.
Fortunately the new battery eliminated the Fuel Rail/SYstem Pressure Too Low error code which would cause the MIL light to appear. Unfortunately the battery drain issue was still occuring.
I started pulling fuses and measured the amp draw for each circuit. I noticed that fuse 19 (Rain Sensor) was drawing .07 amps with the car in "sleep mode". I thought that was unusual so I disconnected the Rain/Light sensor and it has been over 2 weeks without the battery going low in voltage.

Several things that I noticed with a very low battery voltage. When inserting the key to start the car it would not only not turn over but prevented the key from being removed from the ignition. See this Link for more info.
If the door was locked I had to use the physical key to unlock the door but found that that I needed to lubricate the door lock key hole which still took some force to unlock the car. Since I had a lithium ion jump start pack which I kept in the trunk, with a low battery the key fob would not unlock the trunk nor was there a way to unlock the trunk with a physical key. I kept the jump start pack just inside the trunk accessable from behind the rear center armrest, I believe because my car was equipped with the ski package.

I also had sticking buttons on the center console that I suspected that my wife spllled something on it. I took apart the center console to find out that 17 years of dust and grime has caused some of the buttons to stick.
Cleaned up the center console/buttons and they are back to new condition.

I am grateful that I had the patience to discover the cause of the problem rather than throwing needless parts at my car or worse yet paying for a "mechanic" to throw parts at it on my nickel. Granted I did replace the battery before finding what caused the battery drain issue but I wanted to eliminate that as the source of the problem. It also helps that I have a back-up car to be able to let my car sit for days while troubleshooting the problem. Thanks for those of you who had given me tips on troubleshooting my issues.

My 2007 Audi A6 (4.2l) had 190K miles on it.

A6Gary

Nice job troubleshooting.

G-Can

I dont understand at the end, what was the cause, and what was the fix?

A6 4.2 Vier

The cause was a faulty Rain Sensor and the fix was to unplug the sensor. I haven't decided if I will replace it.

AudiAllTheWay

Challenging to troubleshoot that one and good find nice work 👍

Sallad

Good job!

I also cleaned my center buttons a couple years back. I was amazed how dirty it was under that center console.

sswari

Nice Job, Glad you got it figured out and didn't just throw a set of plugs and coils at it.

KevinGary

Great job. I still miss the sound of the engine growl and exhaust note on my old 4.2 40-v.

sswari

Yea, but I replaced mine with a V10, so there is that

Sallad

...showoff...