Yet another power drain

lally911 · 12-25-2003, 02:39 PM

Car is an 85 911 coupe. Right now I have all the fuses (including the three in the engine compartment) removed and the relays from the front fuse box removed. With fuses and relays taken out there is still a .04A drain measured between the negative battery lead and the negative battery pole. Anyone have suggestions on what could be causing this?
Thanks and Happy Holidays!

Keith Lally
85 911 Coupe

beepbeep · 12-25-2003, 03:21 PM

Faulty recifier diodes in alternator?

Por_sha911 · Por_sha911's Garage

Gremlins!

lally911 · 12-25-2003, 04:09 PM

Yeah, but where are they hiding? The alternator was new last spring but its possible the diodes have gone bad. From
what I've read so far the only way to test them is to remove the alternator and have it bench tested.

RoninLB · 12-25-2003, 05:27 PM

not every electrical is fused, or uses relays.. the hot battery cable has 2 wires attached at the battery. maybe disconnect one at a time. and maybe an alarm or something is connected into a non fused hot somewhere

40 ma is to much

Por_sha911 · Por_sha911's Garage

This may be a dumb question but, have you checked for PO modifications like creative wiring, sound system, alarm, etc? If you've found other things rigged up, then there may be one you haven't found yet.

fintstone · fintstone's Garage

Often an alarm is fused seperately.

Lorenfb · 12-25-2003, 06:43 PM

The draw you have is normal, 40ma is about half the max. you should
have. Don't worry about it. Something is using this current and not
run thru a fuse. When the draw gets to 100ma then worry!

It's probably not the alternator, but you can easily check by
removing the red wire from the battery which comes from
the alternator. It's one of the smaller red wires.

Check out this website (www.systemsc.com) on the Problems page
for some additional info on key off current draw.

Have Fun
Loren
'88 3.2

lally911 · 12-25-2003, 06:49 PM

There was a Clifford alarm wired into the ignition switch and powered off the battery but its been disabled. I did leave the clifford wiring in place because I feared disabling my daily driver but now will chance it and rip that crap out.

RoninLB · 12-25-2003, 06:53 PM

Quote:

Originally posted by Lorenfb
The draw you have is normal, 40ma is about half the max. you should have. Don't worry about it. Something is using this current and not run thru a fuse. When the draw gets to 100ma then worry!

only my opnion

I would want to know where 40ma is being drained from.
40ma total is no big deal, even 60ma is normal

What was the drain with all fuses and relays connected ?

lally911 · 12-25-2003, 07:01 PM

With all fuses and relays connected the drain was 40mA. I expected some drain from the clock but saw no change when the fuse was pulled. I've been having problems starting the car after leaving it sit for 3-5 days so I want to know what is using that power when nothing is turned on. The battery is less than a year old so I'm assuming its good. The alternator is also less than a year old so it should be good as well.

dean · 12-25-2003, 07:07 PM

Did you ever kill that year old battery and leave it flat for a short time? I find that if you do that to a lead/acid batt. it reduces the cap. of the batt.

lally911 · 12-25-2003, 07:21 PM

Its drained down three times now to the point where it won't turn over the starter but its not flat dead at this point. I put the charger on it for an hour and then the car starts right up. This just happened Wednesday morning so I checked the voltage on the battery - it read about 12.03.
When its charged its around 12.7 so is this loss of voltage enough to not turn over the starter? Is this possibly a starter problem?

beepbeep · 12-26-2003, 02:37 AM

Charged battery should have more than 13.5V of voltage when free floating, if yours indicate 12.7V then it's toast.
Find that current-leak anyway...diconnect charging circuit alltogether and check again. Even if alternator is in good condition, diode-pack might not be.

dean · 12-26-2003, 05:13 AM

Your batt is cooked IMO. It will not reliably start your car now.

dean · 12-26-2003, 05:16 AM

Oh yea. I assume you have a trickle charger, say 10 amp. If you do, you should leave that charger on over nite to fully charge the batt

weber92037 · weber92037's Garage

Lally, two comments: I had a current drain problem that was traced to alarm wiring put in by po. Resolved when removed. Suggestion. Charge battery fully and check for voltage of at least 12.5 volts. Turn starter to create load and watch voltage drop. If it goes much below 10.5, you can probably consider the battery to be toast. My car battery would drain completely after about 10-12 days with a 70ma current drain. The battery was fine. When the alarm was removed, the problem went away. I can't stand car alarms. My suggenstion is that if you don't absolutely need it, get rid of it. Good luck.

vash · vash's Garage

dont assume your battery is good. i went through the same hell you are going through. i had a one month old optima battery. i also found 40Ma draw at the negative post. just to eliminate the battery as the problem i took it back to the store and had them test it. initial test was good so he said for me to take it home and charge it. lucky me that i had to do some shopping in the area, so i had them charge it for me. it failed halfway through the charging process. if i would have taken it home and stuck it on my trickle charger, i would have gone insane trying to find out why my battery was going dead after two days.

and i hate alarms too, and the people that make us need them. BASTARDS!

Lorenfb · 12-26-2003, 08:13 AM

The KEY is the size of the drain, which determines how long without use
after which the car will start. This assumes a good battery to begin with.
As indicaated in a previous post, a 70ma drain will allow a start in 10 to
12 days. Assuming this, a 40 ma drain should allow a good start in
almost a month.

The draw-down time can be approximated by using the ampere-hour
rating (not cold cranking) to calculate the time; as an example:

Assume a 50 AHr battery and a 100ma drain (.10 amps),

50 AHr/ .10 Amps = 500 hours,

for 70% capacity remaining for a good start condition,
30% x 500 hours = 150 hours or about 6 days.

Also, the assumption about drain is that there are no intermittent
drains, i.e. drains that occur at times other than when the drain
is being measured/checked. This problem does occur often with
some later Porsches, because of all the electronic units.

Have Fun
Loren
'88 3.2

lally911 · 12-26-2003, 11:55 AM

I tested each wire connected to the positive battery terminal and isolated the drain to the bigger red single wire which I believe goes to the starter and alternator. The double smaller reds, the small black, and the main connector all had 0 drain. This car does have the factory alarm as well. Bentleys shows (page 270-12) that 86-89 cars had the anti-theft module wired in this circuit after the alternator so maybe my factory alarm is wired in here as well and is the cause of the drain.