95 Trooper Brake Light issue

bcook65

I have a 95 trooper 4wd.. Recently started having issues where when I have the headlights on, and step on the brakes, my left rear brake light goes out.. Not sure where to look on this one.. anyone got any ideas on this??

thanks

parachautopart

Why dont you take it to mechanic?

stever

Lots of times it's helpful for consumers to get an idea of what the potential problems may be and what the cost to diagnose and fix a problem is before they go to the shop. Do car owners in Pakistan not do that?

thecardoc3

stever said:

Lots of times it's helpful for consumers to get an idea of what the potential problems may be and what the cost to diagnose and fix a problem is before they go to the shop.

How do the consumers get that information when the people being asked don't know the answers?

stever

Sounds like a bad brake interlock switch to me. So you look that part up at Rock Auto and add some labor in. Then when you talk to the service writer and the recommendation is to pull the transmission, you say, er, let me think about it.

thecardoc3

bcook65 said:

I have a 95 trooper 4wd.. Recently started having issues where when I have the headlights on, and step on the brakes, my left rear brake light goes out.. Not sure where to look on this one.. anyone got any ideas on this??
thanks

You most likely have a bad socket, a bad connection between the bulb and the socket, or a bad ground connection.

Pull the lens so you can test the circuits as follows.

The green wire is the brake light. The green with the red tracer is the tail light, and the black wire is the ground.

Do you have a voltmeter? With the taillights on, you should see 12v at the green/red and close to 0v at the black and the green. Then when the brake lights are turned on, you will see 12v now on the green wire. If you look closely at the bulb when only the parking lights are on you might see instead of one filament glowing brightly and the other one not at all, you might see the second one glowing slightly. That means you have lost the ground connection either inside the socket itself or the black wire from the socket to the body. Take your voltmeter and measure the voltage between the black wire at the socket and a good ground, again it should be 0v. If it is, touch the brass body of the bulb and see how many volts you measure. That also should be 0v, but with the problem you described it will likely be higher and

BTW. If you could measure the current flow this would be really easy.

When the brake is applied you should see the same current flowing in the green and black wires. When the tail lights are on, you should see the same current flowing in the green/red and black wires. When both the brake lights and tail lights are on you should see the current in the black wire equal the total of the green and green/red wires. A loss of the ground connection will have current flowing into the socket and back out on the green and green/red wires, with little to no current on the black wire.