So I have a 90' Camry LE automatic and every time I step on the brakes my headlights, brakelights, dashboard and just about everything else dims. Sometimes if I am stuck in traffic and riding the brake the car will just shut off. I have replaced the altenator, distrubutor cap, battery, plugs and wires. I do have a busted sunroof and until just recently it would leak and rain on my passengers and me. When I fixed the sunroof I didn't notice any rust or any signs of water running down to the wiring harnesses and everything. Anyone have the slightest idea what it could be??

 

Does read like an alt or battery issue, too much current being drawn for the current available.

What are idle speeds with brake off and brake on?

Does the car have any high current devices such as a large stereo amp, high output headlights, etc?

Check the cable going from the alt to the battery, the battery cables and all ground points for the cables. A bad cable or connection may cause this.

Try removing all the brake light bulbs and determine if this changes anything. There are other circuits on the brake light switch besides the lights.

 

Sorry for the slow response haven't had a computer since I posted.

I recently replaced all of the bulbs because a while back I had a brakelight problem and replacing the bulbs helped. I also replaced both headlights, and blinkers in the front. Recently in the sudden warm to freezing weather the car idles at 2 grand with the brakes off and when i'm at a stoplight with the brakes on it idles anywhere from .5 grand and 3 grand....and I don't have any high amplified equipment just a crappy pioneer radio.....oh and I checked the cables yesterday and no fault connections.....is it possible that I could have gotten a bad altenator when I replaced it the first time?

 

The idle speed drops or varies when you put on the brake?

Do the lights always dim when you put the brake on or just when the idle speed drops such as under 600 RPM. If the RPM is over 1500 and the brakes applied, do the lights still dim.

It is possible to get a bad rebuilt alt. Use a voltmeter to check battery voltage when engine running. Should be 14-15 volts when engine RPM above 1500. If the low a 13V (idle below 1500) the alt may have a problem.

Does the engine ildes OK when the brake is not on?

Might be the brake booster. The brakes are power assist and use engine manifold vacuum. There is a large hose running to the booster, a large round can bolted to the firewall behind the brake master cylinder.

A leak in the booster valve when using the brakes could cause idle speed variations.

If you can pull off the hose and plug it. Test the brakes to determine if the engine still has its idle issues when the brakes are used.

If the hose is removed the car will not have power brakes, but the brakes will still work.

The hose is a larger diameter, it changes for metal to rubber before attaching to the can. Don't confuse it with the smaller all metal brake fluid lines that run to the master cylinder.