Expert: Roland Finston - 1/24/2012

Question
QUESTION: Roland

I don't know if the abs/brake issue is related, but I figured I'd include it with the issue. I have an intermittent red brake light on the dash that turns off if I accelerate quickly and a near constant (started off as intermittent) abs light on.

The weather has turned cold and each day the car gets harder to start. Now I have to jump the car to start it after a few days. The voltage is 14.4 after start. Before start, when the car is dead, the battery is 11.8-12.2. I don't have a charger. The battery is a cheap-o wal-mart battery from 4 years ago.

This car has been plagued with electrical issues since I've had it.
Any help is appreciated
Shawn

ANSWER: Hi Shawn,
I would separate the brake and abs warning light from the battery drain issue.
Start by check the brake fluid level in the master brake cylinder reservoir.
As for the battery situation. As you have a voltmeter I would assume that it also has a setting for measureing current (mA or amp). If so, disconnect the - post clamp from the battery and put the meter leads between the clamp and the battery post and then read the mA that is flowing when everything is shut off in the vehicle including any courtesy lights. It should be in the range of 25-50 mA or less. If higher then you have an abnormal drain which needs to be corrected. If it appears to be normal or less then you may have a battery which is at the end of its useful life under these winter temperature conditions.
Roland

---------- FOLLOW-UP ----------

QUESTION: After doing the draw test, I have a drain of about 100 mA. I started pulling engine fuses to see where the drain was. It was the #3 30A fusible link in the engine compartment. I held the probes in position for 3 minutes to see if it was just an issue with the battery being reconnected. It was not.

The battery is still pretty low at 12.0V. I'm leaving the car running to charge it some more. With engine running the voltage is 14.5V.

Thank You
Shawn

Answer
Hi Shawn,
While a 100 mA draw seems higher than I would expect, so if you leave the vehicle undriven for a week or so it will definitely lead to a partially discharged battery, particularly if it is an cheap/old one. Here is what fusible #3 powers: charging system, ignition system, fuel injection system, automatic transaxle controller, starting system, theft alarm system. It is not the sole supply of all those systems but plays a role.
Charging system: it provides current to the alternator field coils, but only if the autoshutdown relay is closed (which it shouldn't be with the ignition off).  So try removing the ASD to see if by chance that causes a drop in the current draw. It is the power source for the asd activation coil but that should be out of play with the key in the off position.
Ignition system: same ASD activation coil source.
Starting system: provides power to the starter solenoid via the starter relay, this too should be out of the circuit in the off position.
Automatic transaxle: powers the etax relay and the etax control module, the former should be out of the circuit in the off position, but the module is not. However I would believe the module would not draw that much current when the key is off.
Theft alarm system: same as starting system
So it might be that the transcontrol module is drawing excessively, or the asd relay is drawing in the 'off' position of the key. So try pulling the asd and the tcm plug to see if either significantly drops the draw. Otherwise, maybe a new battery would be a good choice.
Roland