Batt And Brake Warning Light On

NEED HELP. MY 91 .CORROLLA BATT AND BRAKE LIGHT WARNING LIGHTS ARE ON THEN OFF THEN STAYS ON.

AT STARTUP WHEN I REV THE ENGINE, THE LIGHT GOES OFF.

WHAT DA PROB.

GOOD TO KNOW. YOU KNOW WHAT TELL MY FRIENDS, GET A TOYOTA. ITS THE JAPANESE CHEVY.

[TekPhobia]

Worn alternator brushes. Both the brake and battery light come on when the voltage at the alt's "sense" line is less than the output.

It's relatively easy replacing brushes. Just DO NOT go to Autozone et. al. and get a Delco remy. Unless of course, you like replacing alternators frequently.

-Tim

[CraigW]

Check out the truck section there are some good links for alternators, also in the hardcore tech section.

[REN69]

I had that problem before.. Mine was the battery, I changed to a new one and the problem was gone. I had to test everything before though cuz it could've been the alternator too.

Easy test you can perform to see if its the alternator or the battery that's causing the trouble: Losen the positive terminal (+) on the battery and take it off while the car is still running. If the car still runs after you take off the terminal then its the battery that's at fault, because this means the alternator still provides a good current(12V) to the car to keep running. If the car shuts off, then your alternator is gone.

[TekPhobia]

Originally Posted by REN69

I had that problem before.. Mine was the battery, I changed to a new one and the problem was gone. I had to test everything before though cuz it could've been the alternator too.

Easy test you can perform to see if its the alternator or the battery that's causing the trouble: Losen the positive terminal (+) on the battery and take it off while the car is still running. If the car still runs after you take off the terminal then its the battery that's at fault, because this means the alternator still provides a good current(12V) to the car to keep running. If the car shuts off, then your alternator is gone.

NO!!!!!!!!!!!!!!!

That is the absolute worst thing you can do. The battery is there as a cushion for voltage spikes. If you eliminate the battery and there's a voltage spike, there goes your ECU.

I saw a guy with a brand new BMW and his friend did that "test." Well, the car died after a few seconds and it never started again...ECU was fried because the alternator's regulator was shot which was feeding >12V to the rest of the system and *poof*.

-Tim

[bob022004]

I've had the exact same problem....watch your voltmeter....if it comes up when you rev the motor your brushes are worn. Don't wait too long or you'll have to replace the assembly too. I got my assembly with brushes for about 14 bones. Whole lot better than the 130 that advance auto wanted. Check with your local alternator and starter repair shop they can get parts like that pretty easy and most will test the alternator for you too.

[REN69]

Originally Posted by TekPhobia

NO!!!!!!!!!!!!!!!

That is the absolute worst thing you can do. The battery is there as a cushion for voltage spikes. If you eliminate the battery and there's a voltage spike, there goes your ECU.

I saw a guy with a brand new BMW and his friend did that "test." Well, the car died after a few seconds and it never started again...ECU was fried because the alternator's regulator was shot which was feeding >12V to the rest of the system and *poof*.

-Tim

BRAND NEW was the main word in this post my friend... next to BMW. You know how much is "electronically controlled" in these cars?? every single thing in newer cars is electronically controlled. Older cars are not prone to these things due to the fact that electronics are kept to a minimum. Of course if you got a brand new car you're not supposed to fuk around with it unless you know what you're doing. What were the chances of your friend knowing what he was doing? obviously none since he burnt his ECU. You can't even jumpstart anyone else's car because of the electronics.. but hey, I'm sure you and your friend already knew that.

[TekPhobia]

Originally Posted by REN69

BRAND NEW was the main word in this post my friend... next to BMW. You know how much is "electronically controlled" in these cars?? every single thing in newer cars is electronically controlled. Older cars are not prone to these things due to the fact that electronics are kept to a minimum. Of course if you got a brand new car you're not supposed to fuk around with it unless you know what you're doing. What were the chances of your friend knowing what he was doing? obviously none since he burnt his ECU. You can't even jumpstart anyone else's car because of the electronics.. but hey, I'm sure you and your friend already knew that.

Regardless...it's still the absolute worst way to "test" an alternator. The voltage coming from an alternator is "dirty." It's the battery's job to cushiong things.

The correct way to test an alternator is to load it down by turning on headlights (brights), fans, radio, etc. and then measuring the voltage. A healthy alt should sustain the voltage at roughly 13.8V. Anything below about 13V I would be a little concerned (possibly bad diode).

-Tim