Noob with electrical problem

[Benthos]

I have a 99 Civic DX hatchback (manual tran.) that's started having an electrical issue. It began with an SRS error light recently, and yesterday I learned that the driver's side and middle brake lights don't work. The passenger side brake light works. This morning, the cd player (an original Honda car stereo) wouldn't work, and when I tried to turn it on, it just says "Code".

I checked the brake light bulbs and found that both bulbs work on the passenger side light and neither works on the driver's side light. So, it's not the bulbs.

Around the same time all of this began, I started having trouble with the driver's side (hand crank) window. The metal window surround on top of the door was becoming distracted to the door. I suspected that maybe someone had tried to break into the car and had damaged it in the process.

Does anyone have any idea of what the issue could be? I don't know what fuse is used for the brake lights, but if they're all on the same circuit, I wouldn't think it was a fuse problem. Also, does anyone have a recommendation for a good manual that discusses the electrical system?

Thanks for any advice.

Chris

 

[Benthos]

Use a multimeter to check whether the brake lights that don't work get battery voltage. If so, next test whether they get a good ground.

So, I tried measuring the brake light voltages using a multimeter. The readings were strange. I got millivolt readings on both the working and non-working corner brake lights. Aren't these generally running on 12 volts? With the brake engaged, the non-working light showed -8.5 mv dc, and the working light showed 44.6 mv dc.

I'm not an expert with the multimeter, but it's my impression that I can check the ground by choosing the continuity mode, and if it shows a zero reading, that means that the ground is ok (?). With the brake engaged, the working light showed a zero, whereas the non-working light was registering a number other than zero that fluctuated.

 

[Benthos]

Attached are photos from the voltage measurements. I was pressing on the brake and looking back to check the voltage reading. I would insert the red prong into the portion of the socket that aligned with the red wire, and the black prong to the black wire. When I tried setting the range to regular volts (i.e., not millivolts), it would show zero volts, so I switched to mv. Before checking the brake light sockets, I tested the multimeter on the car battery, which correctly registered 12 volts.

I will check the ground tomorrow and report back.

 

[Benthos]

Set the meter to read DC voltage. Instead of the black wire, use the metal frame/chassis of the car. Do the voltage readings now make sense or are they still very low?

An update: none of my brake lights work now. The one on the passenger side doesn't light up anymore.

I set the meter to read dc voltage, and measured voltage for each brake light socket by attaching the red prong to the red wire's side of the socket, and the black prong to the metal frame of the car. I got similarly weird readings as before for both lights. Millivolt readings, and they didn't change when I depressed the brake pedal.

I checked the ground for each by connecting the black prong to the black wire's side of each socket, and affixing the red prong to the metal frame of the car. At first one of them (the driver's side light) indicated a "short" (beeping), but then it changed to "open". The one on the passenger side registered "open".

 

[Benthos]

Re-update: the right brake light started working again.

 

[Benthos]

OH MY GOD I WAS TESTING THE WRONG LIGHTS! I was testing the turn signal lights. It was just bad bulbs! I've never been so happy to be so stupid.