2.6 V6 Cabriolet Auto Charging issue (Help Needed!!!)

[akapieta]

Hi Everyone,

I have had bad luck with this car from the day I bought it and If someone cant point me in the right direction I am considering getting rid of her.

I have a problem with my battery charging system. The car has got a Valeo 90A alternator in and a brand new deep cycle 652 battery in. I have also changed the voltage regulator to a brand new part.

Let me explain the situation:
If the car starts in the mornings, the volt gauge inside the car shows +-13.8V, and then steadily drops as you drive along to +-13.1-13.3V on the gauge. As soon as the electric cooling fans kick in it spikes instantly to 12V and then climbs back to 12.8-13V which I assume is still ok, but the moment the fans switch off automatically the Voltgauge will stay where it is and not go past 13V. It is even worse if the lights are also on, then the voltage will drop on the gauge to +-12.4V. I don't know if these readings are correct, the car's starter gave in about 2 weeks ago took it for a recon also took the alternator to have it tested, starter needed new brushes but alternator reported back fine. If I connect the battery up to the charger and fully charge it (C-Tek charger) everything will be fine for +- 1 week. The first sign I get is that if you unlock the drivers door with the key, everything opens except for the boot, the moment you fully charge the battery again with the charger the boot opens automatically again with everything else.

I changed the starter wire and alternator wire with 16mm2 wire the same that was in but still no change. Checked my earthing straps etc, everything looks solid.

I drive +-13 miles to work and 13 home again, if I get home and hook up the battery charger then the charger shows battery to be only half charged.

Am I correct in thinking the alternator is the culprit after all? I even disconnected 1 of the cooling fans in an effort to relieve the battery a little. (Winter here, so motor stays fairly cool).

I am really puzzled by this and cant think of any solution, I have tested the battery with a multimeter when first started in the mornings and it measures 13.81v over the terminals with engine running.

Please anyone with any suggestions would really be appreciated as to I'm down in the dumps and don't know where to start searching anymore, a friend of mine has exactly the same car, and his volt gauge never drops below 14V even with headlights and cooling fans running.

Thanking everyone in advance.

Pieter

[AndyD]

I would suggest getting the alternator checked out as it sounds like its causing the problem. My 2.8 cabbie had a similar fault when I bought it and I put a reconditioned alternator on and its been fine since.

[VagOrBust]

My first thought would be the alternator as well. While driving your voltage should stay at 13.5-14 volts as the alternator supplies your entire car and your battery with power and in order to do so it should kick out 1 to 1,5 volts more then your battery.
This should only change if you manage to consume more current then your alternator can put out, which is bad, because then your battery will drain.
A minor shortcircuit somewhere in a part with a high rate fuse can cause problems, for example:
I've had a short circuit in the resistor pack that helps regulate the speed of the cooling fan on my S2. This resistor pack had corroded and gave a partial short circuit, but not enough to blow out the fuse.
Good luck!

[akapieta]

Hi guys,

Thanks for your input so far. If I start up the car in the mornings, and keep a multimeter over the 2 battery poles at 2000rpm it never goes above 13.81-13.82, so I assume the regulator is a 13.8V? I am unsure if I could get a stronger one or if this would solve my problem. I am also thinking of changing the 2 cooling fans to a universal 14 inch dont know if this would take strain off the electrical system, I am clueless to start searching for this problem if it is not the alternator. Little bit scared and unsure to start stripping harnasses. I will hook up the multimeter + to the alternator charging wire and the - to the body and see what voltage is coming out there. Is this correct? It couldnt be a relay that is maybe corroded?

Thanks for all the input so far and if you think of anything else please let me know.

Regards

[VagOrBust]

The regulator keeps the voltage output of the altenator at 1 to 1.5 volts over the voltage output of the battery. It does this so that current can flow from the alternator into the battery. The best way to check this is to measure the voltage when the engine is off (minimum 12.5v for a good and full battery), then start the engine and re-measure and you end up with 13.8v, which is fine.
That it dips when the fan kicks in isn't that wierd. I'll check how much it effects my S6 C4 when I drive home in a few minutes.

Have you tried disconnecting the battery whenever you're not using the car to rule out that it's not draining your battery when your car is standing still?

[akapieta]

Hi Vagorbust,

I use the car almost daily, I got home tonight, switched her on, with the ignition on before I started her, voltgauge usually shows 12v, before start up she showed about 11.5V, started her, jumped up to 13v on the aux gauge inside the car. Measured quickly with nothing on just engine running she measured 13.45-13.53v on the multimeter over the battery terminals. Anyway, I went for a 10km drive, got home, and just out of curiosity hooked up the C-tek charger, showed battery was 3/4 full. Does that sound right? Sometimes if I pick up the revs while she was on idle the aux gauge drops a little. Is this normal? (Belt is tight and no sound of slipping). Am I just being paranoid or does this sound right to you?

The reason that I was weary of the "problem" is because my friend owns exactly the same car, but his aux gauge never drops below 14v.

Must compliment you, your car is quite a looker. Let me know about your volt gauge and thank you for your replies.

[akapieta]

Hi Vagorbust,

I use the car almost daily, I got home tonight, switched her on, with the ignition on before I started her, voltgauge usually shows 12v, before start up she showed about 11.5V, started her, jumped up to 13v on the aux gauge inside the car. Measured quickly with nothing on just engine running she measured 13.45-13.53v on the multimeter over the battery terminals. Anyway, I went for a 10km drive, got home, and just out of curiosity hooked up the C-tek charger, showed battery was 3/4 full. Does that sound right? Sometimes if I pick up the revs while she was on idle the aux gauge drops a little. Is this normal? (Belt is tight and no sound of slipping). Am I just being paranoid or does this sound right to you?

The reason that I was weary of the "problem" is because my friend owns exactly the same car, but his aux gauge never drops below 14v.

Must compliment you, your car is quite a looker. Let me know about your volt gauge and thank you for your replies.