deilenberger

The alternator is on the front of the engine, port side if I remember correctly. Much easier to see from underneath the car (after dropping the big plastic diaper pan.) Looking at it is likely to tell you nothing. Do you know how to use a voltmeter?

And how do you know both batteries are going low?

BTW - you still haven't mentioned checking the OTHER END of the ground cable for the front battery. It may be fine at the battery end, what does the other end look like? The other end has been known to loosen up. It's located in front of the drivers seat under the carpet.

deilenberger

Looking at your detailed post above - it appears you have a bad alternator. And it's not a surprise the engine shuts off when the voltage gets too low. It does that to protect the electronics.

Konstantin

Durametrics tells me that both batteries goes low. From 14 v to 12.2 v andthe the engine does not pick up throttle and then dies. At the same time i had avoltometer conected on the front left charging conectors in the engine compartment anthey show the same thing.

I disconected the rear baterie andthe car still runs fine with the front baterie. It starts ok etc. I didnt hadthe time to wait and see if it dies again as before. I will chck later

Konstantin

Yes i checked both ends of the ground cable and both are tight

Konstantin

Btw the front batterie is only 85ah. Is this a big diference to the 110ah that the car should have. BUT it worked fine the last year with the same baterie 85ah even in the winter

bigbuzuki

Both batteries are paralleled when they are being charged.

It is possible that a faulty cell in one of the batteries could be dragging down your voltage bus.

I still would like you to disconnect your rear battery and run the engine while monitoring voltage.

Alternatively, interchange the front and rear batteries and still leave the rear one disconnected with the engine running and monitor voltage.

We are trying to determine which battery is possibly faulty before we start looking at the alternator.

1pcarnut

I'll throw this out just for the heck of it. If I understand what you've been testing, you've been checking voltage while running and stopped but have you done a load test on the battery? This might help tell you if a cell is failing. Don't know about Germany, but here any local auto parts store will do it for free in hopes of selling a new one to you.

Konstantin

test start
at 21:12 14,2v main bat 14,2v starter bat
at 21:53 40 14,1v main bat 12,9v starter bat
at 21:53:51. 12,3v main bat 12,9v starter bat.

this was with a brand new main bat and a used starter bat.

even if i disconnect the starter bat it is the same thing.

now where can i find the alternator regulator? any picts? infos how to check it etc. It must be a problem with it when warm. engine temp 92 degree for 20 min.
any idea how to check the diodes on the alternator?
any other test i can do on the alternator?

Thanks

Konstantin

btw what is error p1299? i got it only after the engine shut off at 12.2v

deilenberger

The voltage regulator is normally built into the alternator. And it is usually replaceable as a seperate part and often includes the brush assembly - at least on Bosch alternators. Unfortunately - the Porsche parts system doesn't show replacement regulator/brush assemblies.

It appears Porsche used air-cooled Valeo in the V6 models, and water cooled Delphi (Valeo?) and Bosch in the V8 models. You may have better luck sourcing the voltage regulator in Germany.. I found a number listed by Googling "Porsche Cayenne Voltage Regulator" - one looks just like a Bosch - but is made by Hella, and lists for $11USD: http://porsche.autoparts-usa.com/por...p-6750707.html

Same one: http://www.autopartswarehouse.com/de...004241121.html - but $17 USD.

Dunno what error P1299 is - it's a manufacturer specific code - does the DuraMatic tell you anything? If you're a paid member at RennTech - Loren can give you the code, or point you to the table of codes so you can look it up yourself. Different manufacturers use the same code number (above P1000) for different faults, so a general lookup won't do. You need the Porsche code listing.

Konstantin

Hello
I finaly found the time to remove the alternator. Not an easy job without the right tools and know the location of all bolts. Maf sensors, hoses to cooler and turbo, intercoolers, bumber, front of the car remove or bring to service position, belt etc etc must be removed o get access to the altenator.

The porsche manual says to replace the cable and conector incl pin 1 and pin2 with new?... Why? I check the alternator and it is the same brand delphi as the one thta was in the car with still porsche sticker on it. New cost at porsche 2000$. I got it online for only 850$. It is the same even the manufact year is the same. 2004 and m cayenne turbo is also 2004.

Anyone knows the reason porsche says to replace the wires with a new alternator?

Thanks

Konstantin

New alternator installed let the engine run for 1h and 1 min. Car still working engine still runs. No problem with engine dying any more. I think and hope problem is solved. I got the same alternator as the old one 948 xxxxxxx part nr an the conector dits perfect. No need to replace the new conector and modFyi the wring harnes any more as stated in the porsce repair manual.

deilenberger

Glad to hear it's finally solved. It was a long journey, but a failing alternator can cause low voltage which can cause the systems to start to shut down. Normally the voltage-regulator on the alternator is temperature compensated, as the car heats up (and the alternator) the output from the alternator should drop, but not below a level where it's charging the battery.

Still pretty shocking prices on the alternators.. I guess there wasn't a source for a rebuilt one? Seems the rebuilt ones in the US are much less expensive (plus there is a Hitachi one available..): http://www.discountautoparts.com/Sho...ulator&mode=PA

Konstantin

This is really cheap in the us. Only 200 us ollars???

Konstantin

I drove my car today after 14 months. All seemed ok was running well etc. Then sudently didnt wanted to start. It started and went iut again. I checked both batteries again. Starter batterie only 12.4 volts. Main bat 11.4 volt!

I changed the main batt and the car was starting.
Imput the starter batter as main and the main as starter. ( just switched the batteries) and now!,,,,,,,,,,,,,,,,,!
Both bateries shows 13.8 v!!! With engine running.
Whats goingmon? I thought one of them is dead.

Is it possible that even i had a charger with 8 ampers on the car this couldnt load the bateries?
Is there a relay which can go bad and do not allow to charge the bateries?
Is it possible that if the main bat is bad i.e one cell bad then the starter batterie wil not be charged?

Maybe both bat went bad after sitting for so long. But! I started the car fine drove with this etc etc. Ater i stoped then it wouldnt start or it started but dies again. After i switched the batteries, main to starter and starter to main then all is ok again.
. Realy starnge. An relay at the batterie either main or starter which can go bad. What othr elctric is circuit can be bad .
What else controlingbthe batteries?