1996 Dodge Caravan brake light trouble

Tiny
BWHITNEY320
  • MEMBER
  • 1996 DODGE CARAVAN
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 223,900 MILES
I'm completely stymied and looking for a new way to approach this brake light problem.

My 2 lower brake lights DO NOT work but, my center 3rd brake light DOES, blinkers work, flashers work, back-up lights work, and all 4 tail lights work -when the lights are engaged.

I've replaced the bulbs, replaced the turn signal switch, and replaced the brake (pedel) switch. (Auto Zone allowed me to return the switches)

Can you give me some direction. If I need to replace the wiring could you suggest an inexpensive way to do this. I'm not sure how to approach this task.

I'm an independant graphic designer and experiencing financial struggles in this economy so I'd like to avoid a repair shop at all costs and don't know where to turn.

Thank you for any help you can offer.
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Monday, September 14th, 2009 AT 8:54 PM

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Tiny
CARADIODOC
  • EXPERT
Replace the wiring? That's quite extreme. That's like replacing the entire roof of your house because of a tiny leak in the rain gutter. The most expensive way to diagnose and repair a vehicle is to blindly throw new parts at it until it works. With every part, new variables are introduced that make finding the original problem much harder. Loose or corroded pins can pull out of a switch connector or get bent over, and go unnoticed. New parts can be defective, or just look correct but have slightly different pins for different applications. Flexing wiring harnesses could pull them loose from their mounts and allow them to droop across sharp metal brackets or onto hot exhaust parts.

On this vehicle, the two lower brake light bulbs are not the same as the signal bulbs, so be sure you replaced the right ones. The fact that the center high-mount brake lights work is proof the brake light switch is working. No need to replace it. Also, a problem with the brake light switch can cause the cruise control to not work. That's another valuable symptom worth noting.

The signal switch is not involved in any way with the brake lights. (That wasn't the case years ago with less complex / more reliable electrical systems). In fact, there is very little to check. The three brake light assembly wires are spliced together near the rear of the floor, in the center. That splice could be corroded if you frequently have water back there. This would be a likely suspect if you knew for sure that both the left and right lights quit working at the same time. More likely though, I would begin by measuring the voltage on the dead bulb sockets while someone holds the brake pedal down. If the wiring on the light assembly is a plastic ribbon type assembly, look for a burned or cracked spot where the print makes a sharp corner or where the copper circuit gets narrow. Since the center lamp works properly, there's nothing to be gained by doing or replacing anything in the front 2/3 of the vehicle.

Also, there can not be a ground problem in the vehicle wiring harness. All the bulbs share the same ground wire, so a problem there would cause all the signal, tail, and backup lamps to be dead too. Look closely at the bulb sockets for signs of brass contacts corroded off, or contact fingers that are bent and not making good contact. In some cases, corrosion on a contact leads to electrical resistance which causes heat, which can cause the plastic housing to melt enough to let the contact not make a good connection. Pressing on the socket might reveal the problem if you do it while someone holds the brake pedal down.

If your vehicle has a trailer hitch, there is a wiring adapter harness that combines the turn and brake light circuits on one side of the vehicle into a single wire for the normal trailer lights, yet it keeps the two circuits separate on the vehicle. I never did figure out how it works, but I remember there are four relays involved. This harness plugs in, as I recall, behind the left rear tire, and is shielded from the elements. If, however, someone installed a generic harness, and used "Scotch Lok" quick connectors, that will be a likely source of trouble. Those connectors are not sealed to prevent moisture from getting into the wires. I think because of the location of the wiring harness inside the vehicle, this is not likely to be your problem, but it's worth mentioning.

Sorry, I can't recall if your vehicle uses the plastic laminated ribbon harnesses or if the wires go right into the bulb sockets. If you have the ribbon harnesses, you will be able to remove a socket and walk away from the vehicle with it in your hand. If that's what'cha got, the turn signal and the brake light bulb sockets should be the same. The bulbs are the same too, so try switching them. If the brake light works now, but not the signal, you know the problem is in the socket. The reason I think you have the flexible ribbon harnesses is I hear a lot of stories about defective lamp housings causing inoperative lights. This was real common on the Stratus and Cirrus, but on those cars, you could buy just the replacement wiring film. You didn't have to buy the entire housing.

If you don't understand electrical theory and how to troubleshoot these circuits, you might consider taking the vehicle to a nearby community college with an automotive program. At mine, I built a lot of cars with preplanned "bugs" for the students to troubleshoot, but then we had community members bring us their cars for more real-life problems. Be aware though, most schools that do take live work will only take it when they are studying that subject. Don't expect them to cater to your specific needs if it doesn't meet their requirements. For example, we would not do a brake inspection during our 8-week engine repair class. To do so would take work away from our local shops that will eventually hire our graduates.

If they can get your car in, repairs will be quite inexpensive, but expect to have to leave it for at least a few days. Also understand it's students working on it. Mine were very responsible and careful, but accidents can happen. We always took care of accidental damage, which was rare, but you should not expect a warranty on any repairs. If that's important, as we used to say, there are plenty of reputable shops in the area.

Caradiodoc
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Tuesday, September 15th, 2009 AT 12:08 AM

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