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'91 Corolla brake light question

I’m in the process of repairing a 1991 Toyota Corolla that my daughter recently purchased. I’m pretty sure the car sat idle for a while, it took me almost an hour using penetrating oil to unlock the lock to get to the gas cap. Anyway, while testing the brake lights I noticed that when I have someone press on the brake pedal, two lights (#1157) in the rear light on each side light. On the driver’s side, the filament on the inboard light is much brighter than in the other three lights. I swapped bulbs, and even bought new bulbs, no difference. Any idea what’s going on here? Could the switch on the brake pedal be oxidized from sitting unused? I’ve seen something on the internet about a “bulb out” block in the trunk that I may need to replace. Could that be the problem? If so, where is it?

It isn’t the switch at the brake pedal.
Have you checked the other three sockets for oxidation?
Which lights come on when you turn the “running lights” on? I’m wondering of you have one socket that’s turning on both the running light filament and the brake light filament when the others are only turning on the brake light filament.

With the headlights off, and the brake on, the one bulb (inboard, driver side) is slightly brighter than the other 3, but only 1 filament in each bulb is lit. A couple of times when I pressed on the brake with the headlights off, the outside bulb on the passenger side got brighter, a couple of times not. With the headlights on, the result is always the same - both bulbs on the passenger side go out. It doesn’t appear that both filaments in any of the 4 bulbs in question are ever lit.

I have an '88 Toyota Supra, and have faced this problem a couple of times. The problem is most likely corrosion build-up on the light socket itself. My solution is to take some fine-grit emery cloth to remove the corrosion on the inside of the bulb socket and take a small screwdriver to scrape any corrosion off the two contact buttons on the bottom of the socket.

Clean out any grit from the inside of the socket, then spread a liberal amount of dielectric grease (bulb grease or tune-up grease) to the socket before replacing the bulb. I did this to one bulb that was showing these symptoms, and after a year or so and when another one started to do it, I did the other 3 at once.

A friend’s 90 Corolla just started doing the exact same thing. I will try Busted’s repair and report back. Might be a couple of days before I get to it as I’m in the middle of another project (which may become another thread).

I had used deoxit on the inboard passenger side socket (turned bulb back and forth 30 times to clear away any oxidation). It didn’t make any difference. I did notice on both sides there’s some black electrical tape, but it looks like a very neat job, like it may have come from the factory that way. Anyone know for sure?

I have had a few of these. The fix is in the ground to each side. The ground is attached with a phillips screw on each tailight. Look and you will see it. Tighten it and it usually fixxes the problem. At thE worst you may have to unscrew it and sand it a little.

Agree with cleaning and tightening the ground wire and the inside of the socket, but suggest that you use red scotchbrite instead of sand paper. Sand paper leaves oxides behind that will lead to more oxidation later. The red scotchbrite is the most aggressive, but the green can be used in a pinch.

I cleaned the sockets and tightened the ground screw, no difference. I used deoxit on the harness connector. Now the passenger side is brighter than the driver side. Thanks for the insights, it was oxidation after all!