Rod Croskery

It's getting cold and salty in Eastern Ontario and our '04 Cayenne S is none too eager to pop its fuel door open. Yesterday with an assistant in the garage I cycled the switch several times. The plunger (which moves at the switch's command) felt gritty, so I lubed it with rustproofing oil.

While experimenting, I found if I rev the engine to 14V the switch is more willing when it has hesitated at 11.9 V by the dash gauge, but is there a hack to open the fuel door mechanically if it won't respond to the switch?

This could prove to be a big deal at precisely the wrong time.

Andy E.

Early Cayennes have a separate fuel filler flap release switch near the tailgate release switch. Later models used the central locking system to lock/unlock the filler flap.

Emergency unlocking of the flap can be performed by opening the RH rear compartment cover and manually pulling on the release ring. This is outlined in your owners manual.

As a side note, if your dash voltmeter is showing 11.9V at idle, you may be due for a new battery. At 11.9V, releasing your fuel filler flap will be the least of your problems.

Rod Croskery

Thanks for the information about the emergency release ring.

As a side note, if your dash voltmeter is showing 11.9V at idle, you may be due for a new battery. At 11.9V, releasing your fuel filler flap will be the least of your problems.

The meter reads 11.9 when shut off, with the various lights illuminated when one is attempting to open the fuel flap. At idle it reads 12.1 -- low by my standards, but consistent with those on my son's S and my friend's Cayman.

The new battery is all charged and sitting on the bench in anticipation of the need. I bought it for my son's before I realized 12.1 is a normal voltage at idle for Porsches (I guess).

deilenberger

Abnormal. My '06 typically ran 13-13.6 at idle and up to 14-14.5 above idle - with lights on.

12.1V is actually a heavily discharged battery.

Rod Croskery

Based upon my experience with every vehicle I have owned to date, I would have to agree with you. Could the gauges read low? When I load tested my son's at 12.1V, it held up well.

I guess I'll put the toaster on Ruby's and see.

deilenberger

Battery voltage vs Charge %

Around 50% charged at 12.1V. I'd put a real DVM on the jumper terminals under the hood and see if the voltmeter on the dash is reading correctly. My '06 the meter on the dash was quite accurate.

Rod Croskery

I think you may be right.

It's confusing to get a voltage reading because there's so much current draw once the ignition is turned on.

Also, I left a door open last night so a fan could dry out the passenger floor mat sponge, so the battery could have been down, depending on how long the door-related lights remained on.

In any case, I futzed around checking voltages, then lit the engine up and heard the alternator really get to work at between 12 and 16V, most likely 14.6. After a short drive I shut down, watched the gauge go back to 13.4, and then (lights still on, remember) drop down to below 12V, far too quickly, to my mind.

I'll make a 2 hr run tomorrow and if it hasn't stabilized, I'll pop in the new battery.

Thanks for your input.

Rod Croskery

I put the new battery in this morning.

Interestingly, the old OEM Porsche-Varta item showed 13.1 V on the bench, separated from the parasitic electrical system of the Cayenne. I figured that was just a surface charge, so I gave it a good toasting, after which it showed "weak" and an unloaded voltage down in the twelves.

The question of whether it will accept and hold a charge remains. If it will, I'll have to look at Ruby's nocturnal appetite for 12V which no battery may satisfy. I suspect the one which came out is toast.

I didn't think to check to see if the fuel door relay will now function. Likely it will.

Thanks for your input.

Rod Croskery

The battery I removed now reads 13.4 V from its perch on the bench, away from the rapacious demands of Ruby.

Today with some trepidation I tried the fuel door switch. Nope. Not a wiggle. I guess I need to get used to the pull-cord in the luggage compartment as part of the fill-up routine.

ScootCherHienie

The symptom you have could also be caused by your alternator not charging the battery sufficiently. If you took your battery out and measured 13.4 volts that's a really high voltage reading. If that high measurement was AFTER charging it with a battery charger, you wouldn't necessarily know if the alternator was working well or not. Cayenne batteries should last 6-8 years since they are inside the passenger compartment and haven't been "abused" by deep discharges (lower life in areas with very cold winters, longer life in areas with moderate climates).

So if there's nothing about the battery that causes you to think the battery could be "done" in less than that 6-8 year life (I had a 911 battery that lasted 11 years in the trunk (all of the 1990s)), it might not be the battery, but could be the alternator instead.

Rod Croskery

It might not be the battery, but could be the alternator instead.

I think the alternator is all right. It pumps out 14.6 when running. The reason I may have switched out the battery early is that it sounded as though the alternator had too much work to do to keep it charged.

I left the 10 amp charger on overnight and it wasn't fully charged in the morning. This looked fishy to me, as well.

It may all go back to the wet floor and the night left with the door open and a 120 v fan on: the lights may have drained down two batteries, instead of one, thereby necessitating an abnormal amount of charging from my familiar tool. 1700 amp hours is a hideous amount of 12 V in a single vehicle. (I found the second battery, apparently hooked to the first, hidden under a bass speaker in the trunk.) See Yes, Virginia... on this board.

nodoors

Does the computer not turn the lights off after 5 minutes or so? My alternator is almost always charging at 13.4-13.5 volts.

Rod Croskery

I was pretty sure from observation that the lights would go off after about fifteen minutes, but Ruby isn't always forthcoming about her 12 V needs, I have discovered.

deilenberger

Oooooohhh... didn't know about that. The usual passenger floor flood? Has it been that way for a while?

I'm sure you know about the potential for corroded junctions inside the huge bundle of wires that makes it's way across the passenger floor under the 2" of foam-rubber-sponge.

It might be worth pulling that up away from the floor an inch or so, and unbundling it. Look for any signs of green corrosion around any junction. If you find any - you need to know how to solder and shrink-fit. The fix is to cut back the wire until the green goes away (water will wick right up the wiring due to capillary action and corrode several inches of the copper conductor) and then splice/solder in a new piece of wire using shrink-wrap to seal the junction. It's not a spot I'd suggest using compression junctions - solder and shrink-wrap is a much better idea for this location. Best is the kind of shrink wrap that also has a melting later inside the shrinking layer - basically makes a water-tight seal.

Thing is - you have to know how to solder - or know someone who does. If you don't - then ask around for an old-ham-radio operator. Offer him whatever bribe he wants to come and splice your joints for you.

BTW - best to disconnect both batteries before starting the soldering/splicing.

Once those junctions start corroding - all sorts of weird **** (TM) can start happening with the electrical system, including modules staying active that should shut off when the system goes to sleep.

FWIW - the 958 series has a small removable bit of carpet on that side that makes it easy to check for dampness under the carpeting. Wonder why Porsche thought that was necessary.. (rhetorical question - hence no question mark.)

Rod Croskery

The first time I discovered the flood (Lesson: Don't spray wash Ruby in sub-zero weather. The sunroof drains don't like it.) there was some water down there but no evidence whatever of corrosion. Mind you, I was too busy with a pair of towels to take anything apart to check. The second drying session dealt with a much smaller quantity of water, perhaps the leftover from the first effort.

Next time in I'll check carefully for corroded lines. Soldering and shrink wrap would be no problem.

As a veteran VW Beetle owner I carefully did NOT puncture the floor plugs to let the water out. That's how one flooded a '63 Beetle floor at every puddle.