03 Accord Rear Brake Light Failed

I have a 2003 Accord 4 cyl. AT with 110,000 miles.

Recently noticed that the passenger side rear stop light is not working. I
have determined that the bulb is good; also, the driver's side and upper
middle brake lights are functioning normally, as are the tail lights, turn
signals, etc.

If anyone has any suggestions I would greatly appreciate them before I turn
it over to a shop without knowing what's needed. Thanks very much!

 

How did you determine the bulb is good?

Is there any corrosion in the bulb socket?

 

Thanks, Tegger. You are one of the main reasons this group is the best.

I first replaced the bulb. Then, I swapped the socket and bulb with the
brake light on the driver's side -- it worked there (and the good one from
the driver side didn't work on the passenger side). I do not see any
evidence of corrosion.

Thanks for your help.

 

Considering that the socket is a fixed part of the wiring harness, I'm not
sure how you could have swapped it.

Take a /good look inside the socket/ on the non-working side. Use a
powerful flashlight. How clean is it inside there?

 

What I meant to say was I swapped the part of the socket where the bulb
makes contact (it pulls out of the other part that's wired in.)

I'll follow your advice and take a good look at the hardwired half under
strong light and keep my fingers crossed, because tracing wires through the
body walls may be beyond my capabilities. Thanks again!

 

Well I tried to see if there was any corrosion in the female half od the
socket assembly and scraped away in there with a piece of steel wire to be
sure -- no luck.

It seems I must now start to follow the bundle of wires that heads toward
the center of the trunk behind the plastic wall. Any guidance or tips on
what to look for or what to do would be appreciated. Thanks

 

I'm a bit confused by your mention of a "female" half of the socket. All
the sockets I've ever seen are one-piece, with the bulb (the male part)
plugging into it.

That said, if there's no corrosion, you've answered that question.

The very first thing I'd do is grab my multimeter.

Remember that brake lights are always dead until the brake pedal switch
provides power. That's your first clue to troubleshooting.

I'd then use a brick, a dowel, a helper, or some other means of pressing
the brake pedal enough that the brake lights come on (ignition can be
"off" for this).

Next, I'd set my VOM to volts, and see if either socket terminal (on the
affected socket) has voltage between it and any handy body ground.

If there IS voltage, then you have a ground problem. Set your VOM to ohms
and connect the /non-voltage/ terminal to any handy body ground and see if
there is continuity. If there is NO continuity, follow the black wire to
wherever it goes, and keep checking for continuity until you find the
break.

If there is NO voltage, then you have a power problem. Follow the colored
wire wherever it goes. When you find a connector, check for voltage to
ground at that connector.

 

<some mistakes snipped>

Let's back up a bit here.

Let's go RIGHT back to the very basics.

Are your brake lights the sorts of bulbs that have cylindrical metal bases
with little bayonet lugs? Do they each have a pair of round contacts on the
bottom?

 

No, that's the confusion. Most of the bulbs in this car are a halogen type
(7440 with one filament, 7443 qith two). They have a molded glass base with
thin, flat wire strips that make the contact. These plug into a 2-part
plastic socket. The upper part of the socket can be released by pushing an
ear/tab (don't know what to call it) under a clip on the lower part.

The brake light is a single filament, and as noted the other two lights in
the system work fine, leading me to believe that the switch at the brake is
working too.

Thanks for your continuing interest, auto electrics is one of my least
experienced areas and I readily admit I'm an inexperienced mechanic!

 

OK, then you should have two wire strips on the bulb that make contact with
the socket, one on either side of the bulb. If so, then troubleshooting is
the same as it would be for anything else...

But there is one caveat specific to this type of bulb and socket:
The socket contacts can spread apart so that contact becomes poor.
Sometimes the bulb (especially if aftermarket) fits poorly and damages the
contacts. Visually inspect the bulb to make sure the wires are straight and
flat. Compare the affected bulb to the one on the other side. Are they
identical, or is the affected one fatter or more mis-shapen?
With a tiny screwdriver, bend-in the contacts on the socket, to make the
contacts grip the bulb more tightly, and see if that improves contact. If
the bulb is aftermarket, replace it with OEM.

I suspect you'll find the cause to be poor bulb-contact due to a badly-
shaped bulb and/or contacts that have spread apart.


As for the electrical troubleshooting itself...

You need a multimeter (VOM). Cheap ones can be had at any auto parts place.
Digital or analog doesn't matter here.

Somehow block the brake pedal down so the brake lights come on.

Then,
1) Pull the bulb out of the affected socket.
2) With VOM set to VDC, check for voltage at either socket terminal, from
the socket terminal to a handy body ground (red probe to socket terminal,
black to a ground).

**If NEITHER terminal has voltage, then you have a power problem.

** If ONE of the terminals does have voltage, then...

1) Set the VOM to ohms.
2) Connect the VOM's probes to the non-voltage terminal and to a handy body
ground.
3) Continuity should be zero.

*** If it's well above zero (10 mega-ohms, for example) you have a ground
problem.

 

If the brake light is a single filament bulb you could just run a wire
from the other brake light that is working.

-jim

 

Thank you so much for your expertise and patience. With your help I was
able to identify and correct a bad ground. I really appreciate you and this
group for all the help you've given me with both my Hondas - as I've said
before this is the best group on Usenet.

 

It's /very/ unusual for a car as new as yours to have a bad ground. Can you
give some details on what you found?

Glad to help.