WillyC4S

Ray, I checked the MY Porsche page and it seems that the 97 wiring diagrams were NLA. I'll call to see if they have something available in another package.

Brad,

I used two digital meters to measure the current draw to cross match the results. My Radio Shack meter was reading "exactly" as yours. The current consumption dropped to ~2.25amps from my previous reading and it went to .06 when all lights were off and alarm off. Final reading after pulling the both fuses was .03, same as yours. I'm interpreting the .06 and .03 as 60mA and 30mA, respectively. I believe that the meter's resolution is not high enough to measure the current correctly. My other meter was measuring about 22mA to about 25mA when both fuses were pulled. Immobilizer didn't add any measurable current draw. Very interesting.

I've fully charged my Optima and I've pulled both fuses out. I'm letting it sit (with the immobilzer activated) for a week to see if the car will start; ultimate test of current leakage.

Check to see if your alarm LED's are showing something funny. A normal car will have the LED's flash for 10 seconds immediately after locking the doors. The flashing during the 10 seconds is a constant 1/2 second or so flash, pretty quick. After the 10 seconds, every second there should be a single flash, not a double flash. An abnormal car (i.e. door open, glove compartment open, trunk open, engine lid open, other weird sensor activity ...) will NOT have the 10 second LED flash and after the 10 seconds, there will be a double LED flash every second.

When my car was having the battery drain problems I remember that the double flashing for the LEDs was happening. I didn't correlate that to an error in the system until I read about it in the immobilizer diagnostics section for the 993.

I also checked to see if removing fuse #11 and #29 would affect the operation of the immobilizer. I took both fuses out and then purposely opened the doors, hood, engine lid, glove compartment when the immobilizer was activated. In each case the immobilizer detected the intrusion and activated the siren. If you run your car w/o the 2 fuses, at least you don't compromise your vehicle security.

I'm letting it sit for now. In a few days I'll re-post regarding whether car starts or not. Got my fingers crossed.

BTW, it really sucks to not fix this problem, but if it's the immobilizer that's at fault then probably easier and cheaper to take the fuses out.

*****

neunelf

Randall and ***** thanks for replying to my previous post.

Randall, Here is a photo of my multimeter.

It is hard to see but at the 5:30 position is the 20m setting I used. Below the 20m is a line and below that '10A'
Within that range on the meter face is 2m,20m and 200m all three grouped in the area labeled 'mA' followed by a dash with three dots underneath.
My leads were pushed into the 'com' and '10a' outlets.

I don't have the wiring diagram for the '96 993 but for fuse 29 the fuse box lid indicates interior light just like ***** has.

If my lowest reading now is .03 by pulling #11 and #29 what should I be looking for as a good end result? A perfect Zero?

*****,
I agree with your thought that the meter's readings of .60 and .30 may be a little off due to a lower resolution multimeter. The multimeter I bought was noting great it was the only digital one available at Walmart, costing ~$19.00.

With the trunk latch in the closed position I set the alarm. Oddly, unlike your experience my light sequence indicated no problem. I get the 20 or so quick flashes in the first 10 seconds then the normal flash per second.

I guess my next move is to pull other fuses to see if the rating will drop even more. <img src="confused.gif" border="0">

Randall G.

Hey Brad,

Okay, I enlarged and lightened your photo. Doing this, I was able to see that your 20m scale is also the 0-10A scale, "10A" being printed directly below 20m in red. Conclusion: our interpretation of your previous readings was correct.

As ***** has already written, 12-20 mA is normal for a pre-993 911, including a 964. Suppose it's possible the 993 was designed to pull a higher at-rest current. But, my intuition tells me 60 mA is on the high side. This would be 3 times higher than a max. normal reading for a 964!
Sure would be nice if someone (a 993 owner) without a battery drain problem would measure their at-rest current drain.

Not sure if this will any help for you, but I've copied below the text of a thread from the old 911 board:

911 Board Archives

964 C4 Battery Drain - What's the deal

964 C4 Battery Drain - What's the deal
Geoff -- Monday, 28 May 2001, at 8:10 p.m.

I have an 89 964 C4 that drains its battery after sitting for 2 or 3
days. This problem has popped up on
this web board continuously in the six months or so that I have been
following it. The most common
identified source of the problem seems to be the HVAC head and/or the
connections to it. The solutions
I have seen range from disconnecting the blower fuse to "resetting" the
unit to replacing the unit to
cleaning the electrical connections to the unit.

Does anyone know of a definitively identified source of this problem and
a related solution (Roland
where are you?).

I have disconnected my HVAC head and am going to see if this stops the
battery drain but even if it
does, I still don't know how to permanently rectify the problem.

Let's lick this little bugger once and for all!!!!

Re: 964 C4 Battery Drain - What's the deal
adrian Streather -- Tuesday, 29 May 2001, at 1:08 a.m.

Dear Geoff, There is not one main problem which causes current drain
problems on the C4. I am afraid
the simple answer is that you have to find the problem with your C4
yourself. This is fairly easy to do.
Disconnect one of the battery leads and connect a multimeter set to amps
in series with the 911 and the
terminal. Check the current drain with all power off "ignition off". The
drain without alarm should be
around 8-10ma and with the alarm 13-16ma. No more. The current drain
with alarm "ON" will fluctuate
with the flashing alarm indication. If you have a current drain higher
than this you have a problem. I would
suspect with your battery lasting 2 to 3 days only you have a drain of
between 1 and 2 amps. Mine was
2 amps by the way. Once you have established you have a drain then the
tedious work begins. You must
remove each fuse one by one. I can almost guarantee that one fuse once
removed will show the circuit
causing the drain. For me it was the RADIO BOOSTER Fuse. Once removed
the current drain fell to
normal. This method is the only one you can employ to find the drain.
Fixing it, well that can be a little
harder. Ciao, Adrian.

PS: Do not forget the green wire which should be connected to the radio
rack alarm switch. This must be
insulated if removed and check for damage if still installed.

Re: 964 C4 Battery Drain - What's the deal
Geoff -- Tuesday, 29 May 2001, at 7:04 a.m.

Adrian,

Thanks for the electrical trouble shooting tips. I guess I was kind of
biased towards thinking that the
HVAC head is the problem because it's performance has some of the
symptoms that I have read about
on this site. These include intermittant blower operation and poor
temperature response. Last night, I
pulled the unit out and discovered that the little fan on the back,
which I assume pulls sampling air into the
unit to determine the temperature, had been unplugged and was therefore
inoperative. I recall from one
of Roland's earlier mails that this fan can draw 0.33 amp if it runs
continuously and that this is a known
failure mode of the head unit.

Anyways, my car also has an aftermarket radio AND alarm installed. I
have read that the radio requires
grounding to a strip in the radio compartment and also suspect that the
alarm may not be installed
properly so you are right in suggesting a thorough examination to
determine the exact location of the
problem.

It is useful to know that 13-16 ma is what we are looking for as,
presumably, the battery should last a
long time between starts at this rate of draw.

Thanks!!

Re: 964 C4 Battery Drain - What's the deal
adrian Streather -- Tuesday, 29 May 2001, at 7:40 a.m.

Dear Geoff, Please do not ground anything on the radio circuit from
original. This causes the drain.
Insulate all original wiring. Especially the green wire that does not
seem to fit in anywhere. Ciao, Adrian.

PS: The 964 has so many electrical systems many of which require power
all th etime albeit low current
drain that any or all can flatten the battery over time. The old DME has
been known to do it as well.

Re: 964 C4 Battery Drain - What's the deal
adrian Streather -- Tuesday, 29 May 2001, at 7:44 a.m.

Dear Geoff. I do not know what size or capacity battery you have
installed but 964s sort of kill lower
capacity batteries. If you had a constant drain of 0.33amps this would
take about a week to kill off your
battery. I have a 74Amphr battery so it would take over 200 hours to
flatten it completely. A flat battery
to me is when the alarm stops flashing and the doors locks do not work
electrically. Long before this the
battery will lose its ability to start the engine, Ciao, Adrian.

Re: 964 C4 Battery Drain - What's the deal
doug -- Tuesday, 29 May 2001, at 9:55 a.m.

Geoff,

Also check the luggage compartment light. A faulty switch can leave the
light on when the lid is
closed--same for the engine compartment and glove box lights.

If this is a coupe, you can lower the battery drain 10ma by removing the
#2 bulb from the clock. This is
the warning light for the convertable top (i think.)

-doug

Re: 964 C4 Battery Drain - What's the deal
Terry -- Tuesday, 29 May 2001, at 12:01 p.m.

Geoff, Doug, Adrian Thank you so much for the info. I thought I was the
only one who had this problem.
I guess misery loves company. My mechanic told me that it was the air
conditioning control unit, so I
unplugged the fuze and the battery still drained down in about three
days. when I'm not driving the car I
now disconnect the battery and connect a trickle charger. Naturally the
battery remains charged, but it's
a pain in the neck to be always connecting and disconnecting the
battery. I guess the only resort is to
begin tracing each circuit beginning with the problem areas that you
have highlighted. Thanks again.

SIR, It's rather simple...
Scott Dunavant -- Tuesday, 29 May 2001, at 11:17 p.m.

Electrical drains can easily be found by simply connecting a test light
to the neg term. of the battery. You
will see the light glow. You should see a very dim light or no light at
all. Make sure your trunk light pin
switch is closed. Wait till the climate control fan stops about 15
minutes or so. Do this test with the alarm
on and off. make sure both doors are closed. Follow this test through by
pulling fuses. Also Door locks
frequently short out. Good luck!

Oh, the door locks are not fused.
Scott Dunavant -- Tuesday, 29 May 2001, at 11:25 p.m.

Follow up... The alarm brain is not fused. The door locks are connected
with this circuit. If a door lock
mechanism shorts out, one can only find which one by disconnecting the
door harness.

Jim Morton

Hate to possibly takes this in another direction...

I had a similar issue with an orange top optima.

I found that Optima had issues with production about 18 months ago. Made me think of this from the mentioning of your batteries age.

I checked lots of current issues. Finally took the battery back and exchanged it. Took some talking, but things have been fine since.

Maybe not as techie, but you might check your battery in another car, or with its continued draw.

.01 cents worth

Jim Morton

WillyC4S

Jim,

I had thought about the issue of the Optima being bad. I was going to do as you said, try it in another car, but decided to give the system one more chance by itself.

If I did find a problem w/ the Optima, how much of a hassle was it to get it replaced? I bought mine mail order and I doubt the guy's going to even remember me. Optima seems to refer you back to the place you bought it for warranty work; not a good sign.

Brad, my final reading was .03 (30mA) after both fuses were pulled out, just as yours is. I suspect that it's lower than that (maybe 25mA then got rounded up). I don't think it's going to go lower than that, but as Randall said, it would be great if a 993 owner who's having better electrical luck than we are, could measure their current draw to establish a correct baseline. I think 60mA is on the high side of current draw though, but definitely better than my 250mA draw. The inconsistent nature of this electrical problem has me worried as well. I'm not into crap shooting w/ my battery and then left stranded when I need the car the most.

Randall, good post about the 964 electrical issues. Good to see that there's expertise elsewhere on the forum.

A few more days and I'll check to see if I can still start the car. If not, then it's leaning towards an Optima battery issue (I hope not, but that's better than a new immobilizer).

The '96 schematic does have a sheet with the alarm (immobilizer) on it. I think in our cars the alarm and immobilizer are closely tied together, but still separate, with the immobilizer being tied into the engine DME system (?) to prevent starting when the alarm is tripped.
I'm going to take a look a that box and see if there's something obvious that could be causing this.

*****

Jim Morton

*****:

I did take some convicing to have the parts store replace the Optima. "Never had one of these go bad..." type of spiel...

Might see if the mail order place will give you a refund and not have to ship the battery back. You have an aweful lot of documentation to present !

I feel your pain !!! It was tough to conclude that the Optima battery could act this way....

Best of luck

Jim Morton

WillyC4S

Update on the battery issue:

The car started up without any issues. No slow cranking or other indication that the battery was being drained after 6 days of standing alone (no battery maintainer hooked up).

So the temporary fix of removing fuses #11 and #29 seemed to have worked for now.

I still don't know what's causing the drain though. Seemed intermittent and not exactly reproducible. Surprised more people not seeing this phenomenon.

*****

neunelf

I'm back with more findings.

Starting, as stated in previous posts, with a .06 (60mA) current I obtained voltage drops as follows:

PULLED FUSE
#29 Change: None
#11 Change: None
#29 & #11 Change: .06-.03

With #29 & #11 pulled then:

PULLED FUSE
#1 Change: .03-.02
#38 Change: flashes between .03 & .02
#38 & #1 Change: .03-.01 but will flash to .02

Fuse 29 = interior lights
Fuse 11 = engine/trunk/glove box light
Fuse 1 = blower inside compartment
Fuse 38= radio booster

I wouldn't think fuse #38 and fuse #1 would make any change but they both did.
All this tells me is that, well it doesn't tell me much of anything other than something strange is going on here.

I now have fuses 11,29,1,38 pulled and have a pleasant reading of .01 (10mA) and flashing to .02 (20mA) occasionally. Yet, this is not comforting since the root problem is not solved.

Doesn't any-any-anyone know a current draw baseline for a 993? Randall, when do you think you are going to buy a 993? Just kidding You seem to be the only Electrically minded person hanging around this board. And thanks for all the guidance.

*****, I agree with your statement "Surprised more people not seeing this phenomenon". I bet other are but are experiencing this problem but are masking it by using the Porsche 'Charge-o-mat' (I think that is what the battery maintainer is called)

Jim, I am running out of solutions and as unique as it seems I am now a believer in changing out the battery. It looks like that's the next semi-logical step. Did you ever take any readings before swapping out the battery? Also what did you put back in the car? Another Optima? A Red top?

Maybe a higher power is a Porsche fan and is telling me to drive my car 'at least every three days'

WillyC4S

Brad,

I'm glad to see that you're making some progress. I'll have to check the other 2 fuses to see if they will make a difference in the current consumption; I didn't try removing all those fuses concurrently, but will do that as you did to verify consumption. I was satisfied with the 30mA draw for now and it seems that at that level it wasn't depleting the battery. There's probably another 10mA to 15mA out there that might not be accounted for.

I wouldn't jump quite yet to the "bad" battery theory until I let the car sit around for a week to see if it didn't hold a charge; my battery did seem to hold the charge. That's probably one of the 1st questions the guy's going to ask you when you go back to request a new battery "how do you know it's the battery? did it drain because of other reasons? ...."

My guess is that in your situation (w/ the new lower current draw) you'll be able to start the car like I did w/o any problems after letting it sit for a week or so.

We seem to be the only 2 w/ this problem. Betcha when the other guys go off of life support, they'll be reading this thread pretty closely ...

*****

krburrell

I know this doesn't answer your original question, but in looking at the TSB (Book M, 1996). It suggests that fuses 11, 12, 13, 29, & 38 be removed to reduce current draw on battery during storage or transportation

neunelf

krburrell, Thanks for the info. Pulling the other fuses in addition to the four I pulled makes sense. I also did get current reductions from a couple of other fuses but I didn't mention them because they were logical and expected; like the computer and clock.

*****, I'm thinking others will be so tired of this thread that someone will solve this riddle just to kill this thread
Please, any thread killers out there?

Randall G.

Hey Brad/*****,

Just finished measuring the current draw on my own car. To be honest, something I had never tried before:

-Initial reading, interior lights on = 1.54A.
-Removed fuse 11 (interior lights/clock for a 964), reading dropped to 120 mA (0.120A).

Now, here is where I got stuck for awhile. I knew 120 mA was too high, but no matter what fuse I pulled, I couldn't get the reading to drop more than 10 mA (to 110 mA).

After scratching my head for awhile, I finally got the bright idea of taping down (okay, up) the trunk light switch (I had the trunk open as I worked). Checked my meter, and the reading was down to 19 mA (normal). Doesn't really make sense, because the fuse that sends power to the switch was pulled. I'm sure there's some sort of complex path by which current is passing through the switch to ground .....

I've reread your posts, and it looks like you both had the trunk closed when you took your measurements. But, if you have a door or the rear lid open, you could have the same effect.

Even if ***** had the trunk open while taking his measurements, I don't think this would explain his initial 270 mA readings.

BTW, here's a link confirming that 25 mA or less is a normal reading, and that over 100 mA indicates a fault:

<a href="http://autos.yahoo.com/repair/results/ques028.html" target="_blank">Battery Drain Troubleshooting</a>