What do I do about my outta-control lights?

Dear Car Talk

Dear Car Talk | Dec 01, 1989

Dear Tom and Ray:

We own a 1984 Mazda GLC. The right emergency flasher only works if we also flip on the right turn signal. After a few minutes, we can flip off the right turn signal and both flashers stay on. Also, when the temperature drops to the mid-thirties or lower, the parking brake light stays on after the brake is disengaged. Eventually, the light goes out after the car has been driven fifteen of twenty minutes. We know that tracing an electrical problem can be a costly nightmare. Should we let a mechanic tear into it? Could it lead to more serious complications if left unattended?
Joe and Debra

RAY: Let's start with the emergency flasher problem. If you change the front and rear bulbs on the right side of the car--making sure you use the correct replacement bulbs--the problem should go away. One bad bulb can wreak havoc on your directional system. It can cause flashers to blink erratically, it can even cause them to blink at two or three times their normal speed. Whenever you experience strange flashing (men in overcoats notwithstanding), suspect a bad bulb.

TOM: The parking brake light problem also has a simple solution. That light can indicate one of two things. The first--as you know--is that your parking brake is engaged. The second is that your brake fluid is low. This may mean that you have a leak, or more likely, that your pads have worn down enough to make the brake fluid level drop.

RAY: Your brake fluid level is probably right on the edge between normal and low. When the car is cold in the morning, the brake fluid contracts and falls below the normal level--that turns the light on. After fifteen minutes or so, the fluid heats up and expands, and the light goes off.

TOM: If you don't believe that things expand when their warm and contract when their cold, Joe, take a look in your swim trunks next time you go in the ocean.

RAY: The solution is top up the brake fluid and have your pads checked next time you bring the car in for service. If adding fluid does not make the light stay off, you may have a leak, so have your brake system checked right away.

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