Brake Light Could Signal Problems

Question: I have a 1982 Honda Accord. The brake light on my dashboard stays on after I release the hand brake on my car in the morning. After running for about 15 minutes, the light goes off. This happens every day. How does the unit work?--J.P.

Answer: Although you may think the problem is in the hand brake lever or the switch that controls warning light on the dash, several other anomalies can trigger the brake warning light.

The light will go on if there is a low fluid level in the master cylinder, which is mounted on the rear wall of the engine. The master cylinder is the unit that distributes hydraulic pressure to the individual wheels to operate the brakes.

Second, the dashboard light will go on if there is an overall system failure in the braking system. This would include, for example, a loss of pressure in one of the brake lines--a failure that forces the braking system to revert to partial function.

Finally, a brake light will also indicate that the parking brake itself is engaged. So, if you release the brake and the light remains on, it could indicate the brake is not disengaging.

The parking brake is quite different than the pedal brake. The lever activates a cable that runs under the car to the rear wheels only. When you pull the lever, it engages the rear brake shoes but does not activate the front brakes.

In diagnosing any mechanical problem, it is always wise to check the easiest, cheapest items first.

In this case, you or your mechanic would first check whether your brake fluid level in the master cylinder is low. This is the likely cause of the problem. The light may stay on while the system is cold, but after the system warms up from several stops, the fluid level would expand just enough for the warning switch to turn off.

If you strike out on this easy fix, then maybe the parking brake is actually staying on even when you disengage the lever. There are many ways to check this, but an easy, foolproof method is to simply jack up the rear end and make sure that the wheels rotate freely.

Finally, if there is a system failure, then you have a potentially serious safety problem that needs a professional diagnosis. The brakes may have lost hydraulic pressure to one whole side of the system.

Q: My 1978 Oldsmobile Brougham has a problem in the dashboard. The gauges on the dash will work for a period of time and then become frozen in either extreme position. For example, the temperature gauge will indicate cold or hot. I have had the alternator checked and the car starts well. So, I thought I'd ask your advice.--R.J.M.

A: You have an electrical problem affecting your engine sensors. A general electrical failure, like that caused by an alternator malfunction, would not cause just the dashboard to go haywire.

The 1978 Olds used a printed circuit board for controlling the dashboard gauges. Over time, heat, moisture and pollution can degrade it, causing the various layers to delaminate. Then, when the board becomes hot, it can act in erratic ways.

A GM dealer or a good electrical shop should be able to diagnose your problem. Unfortunately, if the circuit board has gone bad, it is not a cheap repair.

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