ScootCherHienie

We got our '08 957 last June and immediately began having problems with the battery draining while the car was parked. The non-turbo S looked so perfect, it was difficult to find much that didn't look brand new (cosmetically and underhood & under-chassis) so I wasn't anxious to dump it right away. For months this went on in spite of the drain on the battery dropping to 10.7 ma within 10 minutes of turning off the Cayenne and not locking it, or within a few seconds of locking the turned-off Cayenne. Apparently the drain on the battery didn't start till some time later while the car sat parked. By 4 days the lift gate would begin to fail to open or close but engine cranking was very nearly the same as with a fully charged battery (owner's manual says the rear lift gate is the first thing that will stop working when battery voltage is low). Fully charging the battery would produce another 3-4 days of working fine without charging the battery but sitting parked long enough would discharge the battery.

About 2 months ago, I started using the rotary switch that adjusts the outside rear view mirrors to fold the mirrors in when I park the car in our garage. I fold the mirrors in and leave the mirror switch in the bottom position. I haven't had to charge the battery once during the last 2 months. Left it parked for up to 8 days with no more signs of low battery voltage.

Prior to folding the mirrors in to park the car, the mirror rotary switch was always in the 12:00 position which has squiggly vertical lines. I didn't think much of it. The car was delivered to us with the mirror switch in that position and that icon didn't scream "heated-mirrors-On position". We live about 30 miles east of San Francisco, so very mild climate. Heated mirrors might be useful once every 5 or 10 years around here. By some miracle, the outside mirror adjustment was fine for my wife and me, we never needed to adjust their position/setting. So for almost 6 months the outside mirrors were were always left with the switch in the defrost/heat position. So SOMETHING must have been waking up in the car and letting the mirror heaters operate long enough over enough days to drain the battery enough to get the voltage down far enough that the rear lift gate would stop working. If I continued to drive the car after the rear lift gate stopped working, engine cranking speed did slow down a bit, but it would still start, though I could finally tell the battery was discharged enough to affect engine cranking if running errands with a mile or so between stops.

So if you USE the mirror defrost feature, be sure to turn it off when you park the car, especially if you park at an airport or some place else for a week or more. I have absolutely NO explanation for how the battery drain could measure 10.7 mA after the car has "shut down" completely after being parked and have something "wake up" and turn on the mirror defrosters. But 2 months into this, I'm convinced that was the problem. The next step will be to once again, leave the mirror switch in defrost position with the car parked for an extended number of days to see if the battery drain returns, but I'm not anxious to do that for a while yet. With a 10.7 mA drain on the battery, it should take something like 9 months to drain the battery if you never charged the battery. 10.7 mA is what it takes to operate the security system and key sensors. You will never read Zero milliAmps drain while the car is parked.

I thought perhaps the battery drain had something to do with water infiltrating the vehicle from car washes or rain and did poke around a bit looking for dampness inside anywhere and never found anything (we have a sunroof, but it's the small one). We have had a REALLY rainy winter and the Cayenne has been in some hard-driving rain at 70 mph for an hour at a time so I don't think the car magically dried out, stopping the problem. It has been exposed to PLENTY of water in the last 2 months.

Dilberto

Good observation. I always leave my mirror control in the "auto-reverse tilt down position"

8202632

good find and great info to know. Thanks for sharing

ScootCherHienie

Wait, what? Our car did this for a while, (passenger mirror tilts down when you are in reverse) but it stopped doing that after I disconnected the battery to insert the ammeter to check current draw when the car was sitting parked. I assumed it was something I would have to "programmed" back into the Cayenne next time I have it serviced. The mirror switch in our Cayenne seems to have 4 positions unless I'm missing something: 11:00 adjusts driver's side mirror, 1:00 adjusts passenger side mirror, 12:00 defrost position, 6:00 fold mirrors inward. Is there another position I missed that keeps the passenger mirror tipping down when in reverse? Or is this a difference beteen 955 and 957?

Dilberto

The 1 o'clock **** position defaults my 2006 CTT and 2005 Cayenne S(Comfort/Convenience package only) to dip the rearview so you don't kerb your wheels.

ScootCherHienie

OK, that solves that mystery! Thanks. I probably should have read more of the owner's manual! That was the ONE thing missing when we got the car. There was an 8-inche thick stack of manuals with the car, but that did not include the owner's manual. Found an electronic copy easily enough (free), but not a big fan of reading books on devices. Also scrounged a used manual on Ebay for $35 but read a few parts and set it aside. Need to read the rest of that PLUS the big manual for the sound/nav (though the nav system is so much worse than a $100 Garmin on a suction cup, it's hardly worth bothering with the 8-year old system with its out of date maps when the $100 Garmin includes free maps forever and it has traffic alerts and announcements that include street names. (the Garmin was an Ebay purchase too , "reconditioned" for about half what "new" units go for, packed in a brown box instead of the multicolor original packaging, but it is OBVIOUS this GPS had never been used before and was indeed "factory fresh" (a common thing in the world of "refurb" units, most products like these can't be "factory reconditioned" for what they charge for them. They HAVE to be brand new units nobody has received, unpacked, inspected, tested, repaired, tested again, and repackaged as you would do with a REAL refurb unit. But selling new as "refurb" keeps full-retail sellers happy.

Torre

I always have my mirror switch in the 'center' position, and I've never had an issue. Even when leaving the car standing for 2 weeks.

957 here too and I live in a cold climate.

Dilberto

Haha....that is what my Android phone with Google Maps is for.

Andy E.

Good observation and glad to see that you found your problem. PAG inherited the mirror selector/heater switch on the Cayenne through VW's parts bin. All other PAG mirror switches and mirror glass heater operation is either controlled independently or through the rear defroster circuit. My guess is that either your mirror switch is defective or one of your mirror glass heaters are shorted. Either way, the mirror glass heaters should not work when the vehicle is switched off. Parasitic electrical drains are very hard to source when diagnosing any car that's loaded with electrical accessories. The heated steering wheel is yet one more forgotten item that cannot be switched off and is energized only during lower ambient temps.

A good way to isolate certain circuits is to pull one fuse at a time while having an ammeter connected to the vehicle's battery. This way, you can isolate which circuit is drawing current and try to pinpoint your problem using an electrical schematic.

ScootCherHienie

Once cell phone routing is as easy to use, set, reliable (no loss of cell service), and feature rich as an inexpensive Garmin GPS, I'll switch. Oh, and when unlimited data plans don't cost half as much as the Garmin GPS EACH MONTH. I don't need or use much cell phone data, so we get by with much less expensive per month cell phone bills than we would have with unlimited data. But using cell phone routing would put us way over on data use on our limited plan. No sense spending the money on data I may or may not use.

I have NO DOUBT that at some point GPS devices will be as quaint as phones with rotary dials, old black & white TVs with vacuum tubes, and calculators. But we aren't there yet. GPS devices (at least Garmin's) are still better as GPS devices than cell phones... for us. YMMV.

7 Summits

I use waze daily on my iphone and it does not add a lot of data. Less than a GB/month. Factory nav reroutes the strangest ways. And it also doesn't show you where the LEOs are hiding!

wkearney99

Downside is Waze consumes a beastly amount of phone CPU and battery, making the phone run pretty hot. My iOttie wireless dock seems to be able to keep my S7 topped up, so it's not a net loss, but when I get out of the car it's almost like putting a lit charcoal briquette in my pocket. Summer and direct sunlight sometimes led to overheat warnings on previous phones if I had Waze running.

Still, it IS a handy app and I definitely make use of it if I'm driving through unfamiliar areas.

7 Summits

Never had that problem or noticed excessive heat. I've done 16 hour straight drives, with stops for fuel and bathroom only. Phone is constantly charging so there is no battery drain.

wkearney99

It definitely varies by phone model. Factors like cases and direct sunlight too. But it's worth it given the app benefits!

morrisdl

"GPS devices (at least Garmin's) are still better as GPS devices than cell phones... for us." - sarcasm right?

The only competition for years is between WAZE and google maps. Both work offline, and accept voice commands reliably. My S7 edge wireless charging can keep up with WAZE and streaming music if you turn the screen off. Google maps has "better" turn-by-turn prompts, so I use that for directions. Also run WAZE in background for speed trap alerts. Im still on the OLD Verizon unlimited data plan, but I heard its back. Of course my phone just sits idle now that Im using my in dash WAZE.