How to find a battery drain?
 

What is the best way to locate an electircal short that is draining the battery, as evidenced by a test lamp on a battery terminal? This is not re my P-car but my daughter's 93 Escort, though the procedure ought to be the same. I have pulled all the fuses, and disconnected the alternator output (and radio), but the drain is still there. Is there an optimal path to isolating the culprit?

What is the wattage of the bulb? A certain amount of drain is normal due to an alarm system, clock, CPU memory and such. The first thing to do would be to determine how big the drain is. A wiring diagram would help to make certain that each circuit has been checked. How old is the battery? All wet cell batteries do have internal leakage. Yours may be on its way out. Keep us posted.

George
83 911SC cab/euro

Here's a shorthand procedure for locating a parasitic load:
1. Disconnect pos. (+) cable from battery.
2. ID and disconnect circuits with constant drain (e.g. radio memory, clock, alarm, etc.)
3. Insert ammeter in series with disconnected battery. Typically, current drain should read <30 mA. If meter reads downscale, reverse connections.
4. If more than 30 mA, disconnect circuits from system by pulling fuse, one at a time until offending circuit is isolated. Some circuits on some cars are not fuse-protected (disconnect closest connector)
5. Remember that excess current drain could be in one of the circuits in step 2.
6. Locate and repair source of excess current drain (this could be the "fun" part); faulty circuit insulation/harness, faulty accessory.
7. Circuit schematic is helpful to ID circuit branches.

Sherwood Lee
http://members.rennlist.org/911pcars

I'm going through the aforemetioned proceedure, as I have this problem with my '86 930. Bettery is new, but is drained after 10-14 days. I've gone thru the steps of pulling each fuse one at a time and still have a constant reading of 55mA on my voltmeter.

Any thoughts on next step ? Is there a method of testing the alternator without having to remove it, if this might be the next area to check ?

The standard constant drains on a car are:
Radio (memory function)
Clock
ECU - Electronic Control Unit (memory)
Altenator - back drain through a leaking diode
Alarm systems
Some seat belt systems.
Some air bag systems (sensors)

Hope this helps
Bob