bdrussell

iTrader: (2)

I checked the bulbs, they are fine. I also finally found and checked the fuse, it is fine, when pulled the third brake light that works shuts down.

Any idea where I should look to determine why the brake lights aren't working? All other lights are working.

Thanks
RustyNCA

AAIIIC

iTrader: (19)

Check wherever they ground? I would think they would ground individually, but if they ground to the same point that might have gotten corroded.

Do they work as tail lights, just not as brake lights?

isis

iTrader: (1)

Can you clarify this part. Might help.

AAIIIC

iTrader: (19)

The fuse is not blown. If he pulls the fuse, the third brake light, which was working just fine with the fuse in place, no longer works.

RADEoN

iTrader: (12)

i actually think there is 2 fuses for the brake lights.

bdrussell

iTrader: (2)

First, I haven't seen a car that required the key to be turned on for the brake lights to work, that part sure seems strange to me.

Found there is one fuse marked BAS under the back seat and carpet on the drivers side pod. Car has two "pods" of fuses back there. There is also a relay in the same pod.

Finally, slowed down and thought, damn, since I have two CTS's think this through more.... Had my son get in the V and step on the brakes.



So, the brake lights are the top lights not the middle ones I was looking at. .

Pulled the light cluster off and checked all the lights. Appears they all are the same bulb whether they need two filaments or not? Again, seems strange but okay.

Pulled the top bulbs this time, found both sides had overheated and melted the plastic around the bulbs. New bulbs installed and they work, but still wonder what caused them to overheat.

The fuse is a 15amp, so does anyone know if that is correct? Haven't pulled the seat from my car to see what the V is running.

Cheers and thanks for trying to help. Electrical stuff has always gotten in my head and I don't always think it through....

RustyNCA

AAIIIC

iTrader: (19)

The fact that they overheated and melted the plastic makes me even more inclined to think that the ground(s) could be bad. Figure out where they're grounded to and make sure the connections are good.

bdrussell

iTrader: (2)

Yeah, and I'm not really sure how to track that down. I haven't even seen a wiring diagram for these beasts which would help alot. I hate wiring issues....

That is the beauty of my lil coupe, the wiring on it is very basic.... Headlights, One brake and tail, ignition, electric fan and the airbag valves, that's it.

DMM

A poor ground is not going to cause excess heat. It will only add resistance to the circuit after the load and cause it to perform poorly (ie dim lamp output). The main contributing factor to excess heat in a circuit is a poor connection on the b+ side of the load, most commonly at a loose terminal.

Translation, over time the terminals inside the connector spread causing a poor connection on the b+ feed side of the bulb. This causes resistance before the actual circuit load, and additional current (current = heat) is required to pass through the initial resistance of the bad terminal just to get to the actual load.

If you re-tension all the little "finger" terminals and apply a little silicon grease you'll never have this problem.

AAIIIC

iTrader: (19)

When I upgraded to higher wattage headlight bulbs on one of my other cars, I was blowing bulbs prematurely and saw some signs of overheating on the ground terminals of the harness. Improving the grounds to the chassis corrected the problems.

You may very well be right about the connectors themselves just needing to be tightened up for better contact, but from my experience, bad grounds will cause this sort of issue.

DMM

Interesting. Grounds will cause all sorts of degraded performance characteristics, but excessive heat is not usually one of them save for a direct short. This is why circuit limiting devices (fuses, circuit breakers, etc) are place ahead of the load on the b+ circuit. A circuit limiting device is most often a thermal limiting device as current = heat. Excess current = excess heat, thereby faulting and opening the circuit.

bdrussell

iTrader: (2)

Well, I did both things mentioned here on all the terminals going into the light housing.

isis

iTrader: (1)

The higher wattage bulbs draw more current so the inadequate ground connection was more of a problem under those conditions. It's a secondary cause, which became a problem at the higher current flow. It was a weak point in the circuit. Kind of like a water pipe that is fine at 30 psi but leaks at 40 psi.

The bad ground acts like a resistance and dissipates some of the power that should be going to the bulb. This runs the bulb at a lower than ideal voltage, causing the symptoms you mention.

It's actually the same issue as the loose terminal at the bulb, but the power being dissipated at the bulb connector results in heat at the base of the bulb instead of at the ground connection.