Just started to notice that the lights dim on my 91 camry whenever I press the brake or if I hit the power locks and windows. I even stalled once while in reverse parking. Also notice my radio flicker. I tested the battery and alternator and both passed at Autozone. A friend suggested the brake pedal switch. Any suggestions would be appreciated. Thank you.

Have you tried cleaning the ground cabe? Not on the battery post side but on the tail end where it connects to the car ?

Will try that during my break at work tomorrow. Someone suggested that it might be the ground that goes from the engine to the firewall but I can't find it.?

Will try that during my break at work tomorrow. Someone suggested that it might be the ground that goes from the engine to the firewall but I can't find it.?

Try at the cable first. A body ground can be a flat cable and looks like braided copper. The other cable should be easy to follow (battery cable).

Providing you have good voltage at battery, it is likely a loose connection, Turn headlights on for a couple of minutes, this should heat up the connection(loose connections generate heat). Then you may be able to feel for the Bad Connection?
Do this when Engine and everything is cool.

Providing you have good voltage at battery, it is likely a loose connection, Turn headlights on for a couple of minutes, this should heat up the connection(loose connections generate heat). Then you may be able to feel for the Bad Connection?
Do this when Engine and everything is cool.

Im not so sure about this as it concerns the OP's question. What they appear to be saying is that when there is an increased load after the lights are on. The principle stated by you is a correct one. But Im not sure if it applies here. The OP said after pressing the brakes or using power locks (other load sources).

Grounds are the number 1 culprit. Hey, we're talking a 20 year old car here!
... and see if the one is missing from the pass front strut tower to the engine hook when they did the last timing belt.

After cleaning all grounds, apply dielectric grease.

Califdado3, Since the Op says it happens when an additional load is applied, it is intermittant, and could be a cable connection, relay/socket? Still whatever is causing it to dim, is creating heat.
You could measure voltage from the battery ground and headlight positive, note voltage, then from Battery positive to headlight negative, compare the 2.
If the Lower voltage is from Battery Negative to Headlight positive, it is NOT a Ground Problem.
Test have to be made with headlight switched on.