IS A FAULTY ALTERNATOR CAUSING CURRENT DRAIN OR COULD IT BE SOMETHING ELSE?

1992 Toyota Corolla

Tiny

nostall

September, 21, 2011 AT 10:43 PM

Multiamp current drain when car is off. Both battery light and brake light come on when traveling at moderate to high speed. They go off at low speed and idle and sometimes when brake pedal is pressed. Alternator charges at about 13.8 volts when checked at idle. With car turned off drain continues when output connector is pulled from alternator. Drain stops when input wire to alternator is pulled.

FOUND 327 RELATED QUESTIONS

My Alternator Quit Charging

22 ANSWERS
31 IMAGES

Alternator Wiring Problem

7 ANSWERS
7 IMAGES

4 Answers

Tiny

cup1981

September, 21, 2011 AT 10:51 PM

Sounds as if the battery of alternator have failed, causing the brake light to come on. This is because there is not enough power to keep the system operating correctly. You need to have those tested -- most shops test them for free.

The alternator could be the source of the draw, especially since the draw goes away when the cables are disconnected. So, you could potentially kill two birds with one stone by replacing the alternator. Have it tested though before replacing it -- voltage output is only 1/3 of the testing process.

Tiny

mmprince4000

September, 26, 2011 AT 11:52 AM

Usually when alternator goes, the BAT. Light and brake light come on.

You need to get the alt. Checked for diode and ripple.

Tiny

Wrenchtech

September, 26, 2011 AT 12:23 PM

I wouldn't change anything until you have done some testing.
There is a procedure for finding a battery draw like that.

You will need a digital ammeter and a jumper wire with clips on the ends to do this.
First rig any door switches so you can have a door open without triggering the interior lights and unplug the hood light. Remove one battery cable and attach the meter in series between the battery cable and battery post. Take the jumper wire and also attach it the same way. Leave the jumper wire on for at least 10 minutes to expire all the automatic timers. Now remove the jumper wire and read the meter. Anything over 50ma is too much draw. The way you locate this is to start removing fuses one at a time until the meter drops to normal level. This will be the circuit with something staying on. For the alternator, you will have to disconnect the main feed wire to test that. Determine what components are part of that circuit and check them individually until the problem is isolated.

Tiny

nostall

October, 2, 2011 AT 4:12 PM

No large current drain detected when checked at service station. Alternator then proceeded to burn out while system was being checked at service station. Alternator was replaced. No more current drain.

Thanks for your help
nostall

Please login or register to post a reply.

Alternator Replacement Ford Super Duty
Alternator Replacement Chevrolet Silverado
Alternator testing done right
Serpentine Belt Replacement Acura MDX
Serpentine Belt Replacement Chrysler