High mounted brake light comes on with headlights

I have a 1990 240DL wagaon.

I had a brake light go out last week, bought a new bulb...no biggie.

Next day the bulb warning light on the dash went on again....this time
its weird.

If I brake, all 3 brake lights go on as they should - but so does
warning light on dash.

But if I turn the headlights on, the warning light comes on....and the
high mounted brake light is on, whether I'm braking or not.

I have tied wiggling sockets, replacing other two bulbs.....I removed
and reseated the fuse and the problem went away for about 10 minutes,
then came back.

Any tips what to look for?

Stu

 

Try removing the tail light bulbs, then seeing if the problem is still there
(I bet it isn't). Then try the bulbs one at a time to determine which side
is causing the problem. Then, swap the bulbs to see if the problem stays
with the side or with the bulb.

If the bulb is doing it, replace the bulb. It will either be the wrong type
(single filament instead of dual) or will be internally shorted by a broken
piece of filament. If it stays with the side, look at the socket connection
to the shell of the bulb and the ground connection to the socket. A
voltmeter or test lamp helps, but it can be done without.

Mike

 

Check The tailgate harness were they go through the hinge for breakage

--
"*-344-*Never Forgotten"
Is for the New York City Firemen who lost their lives on September 11,2001.
The official count is 343, but there was also a volunteer who lost his life
aiding in the initial rescue efforts. And I will never forget them as
long as I live,
nor should any American.

 

To expand - the power wires for the 3rd brake light and license plate
lights are in the same harness in the left hinge, they can short
together there. Also, if the tailgate becomes ungrounded the licence
lights can steal a ground through the brake light filaments. (There are
wires in each hinge to ground the tailgate, in addition to the hinges
themselves as well as the latch, so this is unlikely, but I've seen
it.) And as the original responder said, the double filament bulbs in
the taillights can have the 2 contacts on the bottom join together.

--
Mike F.
Thornhill (near Toronto), Ont.

Replace tt with t (twice!) and remove parentheses to email me directly.
(But I check the newsgroup more often than this email address.)

 

Turns out it was as simple as a bad bulb - the new one.

Thanks for you help.

 

A bad bulb where? I can't think of a way a bad bulb could cause the center
brakelight to come on when it's not supposed to.

 

If the filaments were internally shorted together or (more commonly) the
bulb was actually a single filament bulb, the taillight power will feed into
the brake light circuit. The clue that headed me in that direction (or bad
ground at the socket) was that he had just replaced the bulb when the
problem started.

Mike

 

I can assure you James that a bad bulb can cause all sorts of problems. A
bad turn/side bulb in a Pontiac GT was found to cause all the lights to
flash when indicating a left turn only.

Cheers, Peter.