Checking and Repairing Brake Light Problems on a 1995 Jeep Grand Cherokee

Recently I was headed down the road to pick up supplies at the local Home Depot when a driver behind me started flashing his lights at me. At first I thought to myself, well they finally found me, and at the next traffic light he stepped out of his car and ran up to my window to tell me that I had absolutely no working brake lights! Whew what a relief, here I thought it might be something serious. Well, all kidding aside it is a serious situation, and I do not want to cause an accident due to this kind of failure so I took his help seriously. There are enough possible problems on the road that can cause accidents and I do not need broken brake lights to add to this.

I will tell you that this is a really odd problem for me since I am kind of fanatical about keeping the lights working on all of my vehicles. This is an old habit which I am sure is partly from when I used to have a few drinks and then drive home, however those days are long gone now. I suppose that perhaps I have been getting soft when it comes to testing my lights since I feel much safer not drinking.

Another important thing to note is that this model Jeep has the "third eye" light in the upper middle of the rear hatch that works along with the other brake light bulbs. In fact I had previously drilled two little holes into the housing of this third eye light so that I could see that the brake lights were on from inside the car when the brakes are applied. If any automotive company folks are reading this article I would be happy to license this idea to your company for a nominal fee.

Shortly after I thanked this helpful stranger for alerting me to the problem I pulled into the Home Depot parking lot so that I could check this brake light issue out. I always have a voltmeter in the Jeep and so I went forward trying to get a handle on why my brake lights were out. The first thing I will point out is that it is extremely rare that all brake lights stop working all at once, and this usually indicates a major fault like a bad fuse, broken brake light switch, or a burnt wire.

The biggest problem I had with this situation was that my 86 year old passenger and friend was afraid that it would not be safe to ride home in my car. I would never put my passengers, especially someone sweet like Betty in an unsafe situation, so while she shopped for the home improvement items which brought us to the Home Depot in the first place I went ahead and started troubleshooting the problem.

Typically in any vehicle which uses DC voltage to light the bulbs you will lose a lamp here and there but you would certainly almost never lose all three brake lights at once. So in terms of troubleshooting, this led me to believe that the fault would be in the front part of the circuit, which would be the fuse or the wiring from there to the lights. Checking the fuse and lamps with a voltmeter I found that those components were all in good working order and therefore the fault could only be in the wiring or the switch?

Using the schematic in my automotive repair guide that was purchased specifically for this model I discovered that there was only one component between the fuse and the brake light bulbs. That one component is the brake light switch which is located just above the brake pedal underneath the dashboard. This switch sends voltage to a small relay under the dash which sends power to the brake lights when the brake pedal is pressed. This switch is a few inches long and wide with a wire connector on it that carries six leads, some of which are for the cruise control.

Using the voltmeter I verified that power was indeed getting to this switch but that the signal was not making it out of the other side of the contacts. This led me to believe that the switch had failed internally. Since it was still light outside, and having no access to a new switch at the moment, I decided to use my flashers and parking lights to get my understandably skittish passenger home safely. We were one traffic light and less than three minutes away from her house so I felt that it was an acceptable level of risk to drive her home and then figure out what I could do to fix this problem.

I do a lot of work alone where there is often no-one around to lend a hand and so I am always creating ways to do things that typically take three hands with two. Ask me about the time I got an F-150 stuck in the hills along the Ohio river and pushed it out with a 4 by 4 post while the truck was in Drive with gas pedal pressed down!

One simple way to activate the brakes is to place a board between the front edge of your drivers seat and the brake pedal then adjust the seat until the board is activating the brake lights, once the brakes are activated you can go to the rear of your car and check the lights. On this Jeep it is easy to do this since the power seat controls are on the outside edge allowing you to move the seat to exactly where you want it.

Once I got the Jeep back to my garage at home I took the stop light switch out from under the dash, which was the hardest part of the job, since you have to be a contortionist to get in there to undo the wiring clip and remove the switch. The wire clip has a red snap retainer that has three prongs which all need pushed in at the same time which is nearly impossible while lying upside down with your back across the door threshold. Once the wire harness is unclipped then you have to figure out how to remove the switch from the metal bracket it is mounted on. This particular switch has a square end that is keyed into the metal bracket and with pliers you gently twist the body about 22.5 degrees counterclockwise which unlocks the built in plastic retainer on the front end of the switch. This action allows you to pull the switch back towards you for removal.

Checking on-line I found a new switch just like this one at a local auto parts store for around $12. I had to know what made the old one go bad so I took it to the workbench and carefully pried the plastic body apart to expose the internal mechanisms. This switch uses a series of contacts mounted into springy copper tabs which touch against each other when the brake is pressed. There is a plastic plunger which meets the pedal that is spring loaded and is designed so that it springs open when you move the brake pedal away from the plunger.

What I found inside the switch was that the first copper tab which was responsible for passing current to the brake lights was broken off at the tip where the plunger mechanism touched it. This copper blade is very thin and over time the flexing seems to have cracked it off. I cleaned the tiny copper pieces with fine sandpaper and using a gas torch I soldered the broken copper tab back together using high silver content solder. This special solder can take a lot of heat before it softens and it will not corrode. So I tested the action of the switch to be sure it was making the brake lights work, then I re-assembled the entire thing, and put it back into the bracket under the dash.

I suppose it would be nice to have a built in failsafe on our cars and trucks but that would probably add too much to the cost. Since this car is fifteen years old, and considering the part was only twelve bucks, it is probably not a bad idea to change this switch out every five or ten years.

As of today it has been two weeks and the repaired switch is working just fine. I have the new switch in the glove box and will snap it in place the minute I see anything go wrong with the old one. I have to know how long my repair will work before it fails. Then I will just have to crawl back under the dash and snap in the new switch.

So if you find that all of your brake lights are off and the fuse is okay then it would most certainly have to be this switch. Logically this switch is one of those components in your car that gets a lot of use every time you drive. Therefore it is not really too surprising that it would fail eventually.