hoodlight off (I put a tin can under the plunger switch), alarm fuse intact but alarm switch turned off.

Ron, could it be a problem with your alarm?

 

I did tried it again with **** setting to 10A and the value is the same, just a digit forward: 0.76amp (760ma), 0.05 (50ma), and 0.02 (20ma). So even with alarm armed, I have 50ma draw. Look like it's normal, am I correct?

Today, I hooked the multimeter to under the dash while driving around and here what I got.

Engine not running... meter: 12.63v (morning). Gauge: close to 13v. Measuring at noon (hot) is 12.83v
First minutes of engine idling... metter: ~13.4v. Gauge: ~14v
Driving for several mins... meter: 14.5v-14.6v. Gauge: 14.9v-15v

So look like my current drawn is ok. My charging system is ok. My interior gauge is bad, It is displaying around 1/2v more than the voltage actually is.
Original question was why I went through batteries so quick? Maybe mulitple reasons?:
1- My after market alarm is taking too much current: around 30ma or less. Is this too much?
2- I didn't drive the car often, sometimes left it until the battery died, then jump start and drove.
... but why my other mordern cars can be left undriven for several weeks, up to over a month but my 911 can't? Is there still something wrong/unchecked or that is how our car is?

Rusnak,
The year before I replaced batteries twice. Last year, once. This year once, just last week. I also checked my Lexus and the drawn is 30ma. Is that a lot different between 30ma and 50ma? Not much right? But my car won't start if I leave it a week or 10 days. Also, I went through batteries so quick.
If you say alarm switch turned off, meaning no chirping/arming when you press the remote control. Then it is the same as you pull fuse, maybe...
Your pic, is that 220ma? Doesn't make sense. It should be 22ma, I guess.

 

Rusnaks clamp is in fact showing 440ma, But current clamps become hugely inacurate in the ma range as that is not there designed purpose.
I would say 30-50 ma should be fine. I would just pul the alarm fuse and see what happens. older porsches in general I hear may not sstary over a cuple of weeks. I am not saying they all do it but i have heard this many times and most people who leave it use a battery tender I would say . Also you don't knw if it is drainng the same all the time. I would think popping the fuse is a good start

 

I agree with Ice. The alarm could be fine, but just to be sure it couldn't hurt to pull the fuse for now. The reason I say this is despite what you are seeing on the meter, your car is draining batteries and you need to find out where. Since the clock isn't the culprit, it has to be something that is either "hot" with the key off, or the alarm. Anything else directly wired to the battery?

 

Ice,
are you talking about rusnak's case or my case? Rusnak's show .22 on the LCD. It could be 22ma or 220ma. How can it be 440ma?

rusnak,
I did pulled the alarm. Without alarm fuse and hoodlight off, it's showed 20ma. It can be between 20ma-29ma since my meter doesn't show another digit. I might pull the clock and see but I really want the clock there. Worst case, I'll a a cheap battery digit clock for $1 buck somewhere

 

That meter is showing .22 amps (220 mA),..not 22 mA in the least.....

Doyle

 

..sorry guys just a brain fade as the 40Amp scale distracted me . My only point was it is difficult yo get miiliamp accuracy on a device ranged to 40Amps but as you can see it is high current measurement device.

I would just leave that alarm fuse out for a couple of weeks and see what happens.

 

I know, I was like "lordy, lordy that is a lot of draw".

I should have gone back to test it again, see if the draw came down. I should have disconnected my stereo stufffirst but it difficult jut to get to the battery, so I can't get in there to easily test separate draws. What I do know is that my battery is probably over 90% charged.

I would try disconnecting your alarm first, then ciggy lighter fuse which is also the interior light fuse next. There is a parasitic draw somewhere.

 

Back to my alternator for a minute...

Here's the latest:

I charged the battery overnight. It read about 12.8 volts after charging. I let it sit for an hour or so, and it read a bit lower, but not much. I started the car and, of course, it dropped due to the draw of the starter. I watched the volt meter as I revved the engine. Nada. Zip. It didn't move at all when I revved, and in fact it dropped a bit as the battery powered the various electrical bits in the car.

So, it's pretty clear the alternator is shot. I'll drop it off at the rebuilder this week. I'll also take the battery in to have it load-tested. If it's bad, too, I'll replace it.

Thanks for the help, guys.

 

if it never went above battery voltage it is TOAST ..

 

Ice: Yeah, it never came up. In fact, the voltage went down as the battery discharged. Clearly the alternator is bad.

I've got the battery on charge now to top it off. I'll take it with me to the rebuilder to see if he can load test it.

Stay tuned....

 

I learned a big lesson last week. That is one meter might not be correct. I have a gauge in the dash and it showed high voltage. Tried a multimeter just for the heck of it, but it turned out my gauge is bad.

 

Are we over thinking the problem here. Turn the headlights and ignition switch on. The try to start the car. Can you hear the relay? Result bad battery.

How I would start the process. Remove and clean the battery terminals and inside the cables. If no improvement, remove the battery (with some difficulty) and take it to an autoparts store and have them do a load test. If bad, buy a new battery, then test the alternator. Most service stations with mechanics will test it for you for free, so will Pep Boys or Autozone. This is a test with the engine running. Now you have your answer. Known good battery, good or bad alternator. Fix.

 

I dropped the alternator off at the rebuilder today. It should be ready today or tomorrow.

While I was there, I had them load-test the battery. It checked-out fine, so maybe I dodged a bullet there.

Hopefully the car will be back up and running this weekend.

 

good news, scott. Before you put the belt on, try turning the fan by hand slowly. If any of the fan blades hit the fan shroud, tighten the little nut opposite of the scrape. Do not overtighten the nuts that hold the plastic air deflector or it will crack.