nickmarrone2

Hey everyone,

So I have a 2002 audi a4 1.8T and there seems to be something wrong with the electrical system in my car. While driving the car died on me and seconds before it died the RED BATTERY light came on. Luckily I was in traffic going about 10 mph and I was able to just turn the car on again with the key. I went straight to NAPA and tested the battery and alternator and the battery was super old and not much power left in it, so I bought a new one. About a month later it happened again. The same exact thing with the RED BATTERY light and car dying. I tested the battery and alternator again but this time they both were in great shape. It was a new battery after all. So something seems to be shorting out maybe? Also, not sure if related but the car has a HARD START most of the time. When I turn it on it cranks but won't fire up right away. This usually happens after it sits for a few minutes and if I am driving the car around and making frequent stops it will usually start up easier. Not all the time though. Most mechanics have not been able to really help me out so far. Any ideas?

Please Help and Thanks!

W261w261

When you said you tested the alternator, did you check the voltage when the car was running? It should be almost 14v, versus 12.5 or so when car was stopped.

Your hard starting could be a fuel pump going bad, or the engine speed sensor (crank position sensor). Instead of letting it crank until it starts, turn it off after a couple of seconds, then try again.
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nickmarrone2

Today the mechanic checked the CPS and said it should be fine. The pressure in the line won't hold so there must be a leak. I think the fuel pump is the issue. I also have code P0455 (EVAP system leak detected, large leak) probably related? There is no gas dripping out and I did check the gas cap.

As far as the battery issue goes, I checked the alternator while the car was running and it read just above 14v. Checked it twice with 2 different people. Battery and alternator are good, but something seems to just short out while driving. Not sure why. Also, only the red battery light came on seconds before it shuts off, not all the dash lights. It's really strange.

W261w261

I had a friend a few years ago that had a similar problem. The car would shut off while driving because of a low voltage state. Turns out the ground connection to the motor was loose, which did not reveal itself while the engine was idling. As the car began moving and vibrating, the ground circuit opened and the alternator was unable to charge the battery (sometimes). So you might check your grounds and clean them up.