Questions and Answers

Cadillac Seville Kills Batteries Overnight Q. Vincent, I have a 1991 Cadillac Seville 4.9 liter engine with a new battery. Question, while overnight the battery goes dead so I am unable to crank the car. Wondering the easiest as possible to check the system as to the problem I do have a Simpson and a Meger. I think it has a ground fault but I am not sure how to test for it, or if it can be checked on the computer at the dealer.

Also, Vincent, the sunroof leaks badly. Just started. I blew out the drains on the front and have been looking for the ones in the rear that drain under the car so I can blow them out. Also can't find where they drain to. Please help.

Thanks,
Bob

A. If the battery is draining overnight, you have a parasitic draw killing the battery. The following procedure may be used when testing for parasitic loads.

1. Disconnect battery negative cable.
2. Install side terminal adapter.
   1. Install a battery side terminal adapter, AC-Delco ST-1201 or equivalent, in the negative terminal of the battery.

3. Install nut to cable.
   1. Install the other ST-1201 or a 3/8" nut with standard threads (16 UNC) on the negative battery case attaching screw to assure a good electrical contact with the metal face on the cable for testing (add a washer behind the nut if the nut does not contact firmly). Yellow or black finish nuts are generally non-conductive and should not be used.

4. Install high capacity ammeter.
   1. With all lights, accessories, Retained Accessory Power (RAP), and the ignition switch off, connect a high capacity ammeter (at least 10 amps) from the negative battery cable to the side terminal adapter. This high capacity ammeter is connected to verify whether or not a high current draw is occurring at a constant rate. It is this type of high current draw that will blow the fuse in lower capacity ammeters. Current is drawn for some time to initialize the CPS. After the initial draw occurs, the ammeter reading should drop below 1 amp.

Parasitic Load Diagnosis Procedure

NOTICE: If a high capacity ammeter is not available, install a section of heavy wire (preferably battery cable section) between the existing battery negative cable and the side terminal adapter. Allow ample time (approximately 30-60 seconds) for the initial draw to occur or check for reduced current with an inductive ammeter (current clamp) and proceed to next step.

5. Install DVM
   1. With the high capacity ammeter or battery cable section still connected, connect the digital multi-meter, set on the 2000 DC mA range, in parallel with the high reading ammeter.

6. Disconnect high capacity ammeter.
   1. Disconnect the high capacity ammeter and take the reading with the digital multi-meter. A current draw of 5O mA or less (25 mA is normal) indicates that all lights and accessories are off and that there is no unexplained current draw. Care should be taken to allow for a time delay before reading the meter because of the Electronic Level Control feature.

7. Determining the source of the drain
   1. Once it has been determined that a parasitic drain in excess of 50 mA exists, a visual inspection of the vehicle should be conducted. Check to see if there are any unwanted lights on, motors running or switches/relays activating.
   2. If current draw is above specifications listed in the standby current load chart, remove system fuses one fuse at a time until the current draw returns to a value less than or equal to the specifications listed.

8. Check charging system.
   1. If a battery becomes discharged and no excessive current drain is found in Step 2 above, the operation of the charging system should be checked.
   2. If no cause for the draw is immediately apparent, it may be possible to narrow in on the source by systematically removing fuses and circuit breakers, one by one, from the fuse panels. This should be done while monitoring the ammeter so that a disruption of the drain will be evident. Refer to Figure for average and maximum parasitic loads for various vehicle components.

9. Driver related condition
   1. If no cause is found for a discharged battery and the battery tests good, a light may have been left on, or the driving habits of the owner may be such that, especially with many short trips and repeated starts, the generator does not get a chance to recharge the battery between starts.
   2. If this situation is suspected, the driver should be instructed in ways to reduce battery drain. Limiting the use of the rear window defogger and setting the Twilight Sentinel on the minimum delay, etc, are helpful in this regard.

As for the sunroof drains, there is one in each corner. The rear ones may be tucked under the roof panel. I don't have a body manual to get a diagram, but you can find a body manual for your car at the local public library in the reference section.

Component Parasitic Loads