I bought a new battery a month or so ago after my 04 S failed to start. FFW to a couple if days ago, I noticed the rear hatch wouldn't open -- classic low battery sign. But it had been sitting for a while and it started fine so I convinced myself all was fine

Now this morning, it started fine but on my way to work I noticed the volt meter showed no charging at all. It's dark out and everything in the car appeared to be functioning normally with headlights on for my 20 minute commute. I didn't even get a warning or any other alerts.

Simply the battery slowly getting weak over time and the charge gauge all the way to the left. Only two symptoms. No warning lights

Wonder it it will start when I get off work
..

I did some searching but didn't see anything with my unique symptoms.

Any ideas?

 

Normally will see a warning if its not charging.

Measure the voltage at the jump posts in the engine compartment, with a DVM. With the engine at idle it will normally read 14 volts, a bit more with all accessories turned off.

The voltage gauge could be toast, but there are no reports of defective dash volt meters that I recall.

The slow battery drain could be a different issue, check the charging voltage and let us know. Some auto parts stores will do this for free if you don't have a meter.

 

Will check it later today. Just a regular multimeter, correct?

 

I believe your 04 S may very well have 2 batteries - the starting battery in the trunk, and everything else battery under the driver's seat. Early Cayennes were like this. If so, this would explain why you have no trouble starting - the trunk battery is used exclusively for that.

But, the voltmeter in the dash shows system voltage when the car is running - what the alternator puts out, not the battery voltage. Even with dead battery the voltage should come up after a few minutes, especially if you turn off heater and headlights (big power draws from those) and rev the engine some. If the voltage is still at 12 with headlights, heater, audio off by the time you get to work, and a voltage meter confirms that, you have a problem somewhere.

 

Thanks. FYI, my 04 does not have a second battery

 

"Charging gauge at zero"

??? What gauge?

 

I think he is talking about the voltmeter where the boost gauge is on a turbo model.

If your alternator is dead, the car can run for about 25-35 minutes on a charged battery before your dashboard starts lighting up like a Christmas tree. Check the voltage under the hood at the jump terminals as v10rick said, and perhaps go back and make sure you got your battery are terminals tight before you do any searching about how much fun an alternator replacement will be. Hint: you are in for a real treat! How many miles on it?

 

I use a digital multimeter for this.

 

Yes the voltmeter is what I'm talking about. I'll test today but gotta wait until after the weekend to open up the battery. I'll update in a bit since I'm about to go see if it starts and if the gauge reads anything. Just need to limp home. Haven't seen a single light on the dash yet. I'll be back
Oh, it has 100k on it

 

Started fine and voltmeter is at 14!!!(???)
Gonna drive it home

 

14V is spot on. Sounds like there is an issue with the dash meter.

You may have an excessive parasitic load on the battery when parked, causing the no start condition.

There are numerous always hot circuits in the Cayenne that could cause this. Add to that corroded wiring from clogged drains. Not the easiest fault to isolate.

 

Drove home fine with the needle at 14 the whole time. Headlights and wipers on.

I have no idea why the gauge pegged left this morn. I'm going to roll the dice and drive it again tomorrow morning.

I swear to god my Cayenne likes to psychologically torture me.

 

In your OP, when you said "showed no charging at all" did you mean that the gauge was showing around 12v, as in battery voltage, or that the gauge stayed in it's parked position all the way left? If it was all the way left, then the gauge is definitely the problem, as no way your car would've started with anything less than 12v.

The gauges are just actuators with electronics determining their position, not like old-school gauges used to be where the gauge was connected to something.

 

When it was acting up, it was pegged left and no warning lights on the dash.

But according to others here, it reads the alternator output, not the battery level, so it should have nothing to do with the starting.

At any rate, I'm going to drive it again this morning. Fingers crossed...

 

Well, everything is back to normal I guess. Just chalk it up to another Cayenne gremlin.

No surprise though since I get a few other weird things happening from time to time, some of which go away with a restart of the engine. Like, once in a while, when I turn the engine off, I'll get a lights-on buzzer. I turn the light switch and it won't go out. I look outside and the rear fog light is stuck on. When I start the car back up then turn it off, the problem goes away.

Or the sunroof will open about an inch all on it's own while I'm out of the car. Or the center LED display will work fine sometimes, other times it's barely visible, etc, etc

Thanks for all the replies