cayenneguy05

Hey everyone! First of all I would like to introduce myself on this forum as it is my first time posting here. My name is Sebastian, and I own a 2005 Porsche Cayenne and a 1989 Porsche 928 S4.

I have ran into a little problem though. I took my 2005 Cayenne into the mechanic because my left headlight was very dim and then on the next 2 days my other headlight bulb was very dim also. I figured that the bulbs were no good so I changed them myself. They worked for about a few days until they have started being dim again. I thought it was the quality of the bulb but the mechanic who is an expertise in porsche had said that the bulbs were perfectly fine and that the problem was somewhere else.

I was wondering if someone knew what might be going on, as this has troubled me for the passed month and a half and I am desperately looking for a fix in this!


Hope in getting a response,


Cheers.

gnat

Have your battery and alternator checked. They are the most common reason for electrical issues in any car. If one or both are starting to fail all kinds of weird stuff starts happening in modern cars.

Don't just test the battery. A bad alternator can kill an otherwise good battery so just replacing the battery without knowing the state of the alt could lead to needing another battery soon. If its still the factory battery though then my money would be on just needing a new one.

If it is a bad alt, see if you can get the old one diagnosed. If its the voltage regulator that failed you might have a short somewhere that could wind up killing the new one too. Finding it, however, is not likely to be easy.

grohgreg

I don't know what type headlight system was used in MY2005. Might it need new ballasts ? Otherwise, check battery voltage when keyswitch is off. Should be about 12.2 volts DC. Then make sure belt tension is tight, and not slipping at the alternator pulley. With leads still on battery, start engine. Voltage should jump to over 14 volts to replace the charge used to turn the engine over. As charge is replaced, voltage should drop slowly to about 13.2 volts. If you don't see that happening, have the starting/charging system checked at a auto parts store to see whether the alternator's not putting out enough juice - or the battery's not accepting it. They do this at no charge, with the idea that you'll buy what's needed from them. Either way, it's bad - because the engine electronics will stop working when they see less than 9 volts or so. If you DO see the above numbers in the sequence described, it's likely the voltage regulator. That's something an auto parts store test can check as well. Or save yourself all that testing, and just let the parts store guy tell you what's wrong.

//greg//

gnat

Don't trust a simple volt readings. While low volts with the car off can indicate a bad battery and out of spec volts can indicate a bad voltage regulator on the alternator, it's the amps both provide that is crucial to the charging system.

Unfortunately I've had way too many (mostly self inflicted) electrical issues with my Escape and seen weird things happen. One case had the battery and alt giving me expected volt readings, but ultimately we found that the alt was only putting out half it's amps and the battery had a couple of bad cells.

Load testing and measuring the amp draw (which means you also need to know the expected draw with different items on (headlights, heater/AC, etc)) is the only true way to know how they are really doing.

grohgreg

Simple tests are meant to narrow down the problem area. For those who understand the results that is. Like I said, auto parts stores do this for free. But sometimes it's just more expedient to use a multimeter in the driveway, than it is to drive to a parts store or repair shop.

//greg//

gnat

I agree. I'm just making sure that just because the readings on a voltmeter look good it's understood that it doesn't rule out the battery/alternator as a problem.