Look for bad earth connections, that is bad cable connectors between the
metal lamp holders and the cars metal body.
Try with en extra cable.
Or are there bad bulb sensors here that complicates this, anyone?
Rotten earth cables on both sides? Was the car flooded recently?
Bulbs are ok?
I would not advise the original poster to do that himself - you could
do something awfully wrong unintendedly. Electrical power in cars is
powerful, despite the mostly low voltage. Find a friend who knows
about these things.
On 29/11/12 00:58, firstname.lastname@example.org wrote:
It's probably easier to just add another earth connection.
Assuming all the lights' earths are connected to each other, but not to
the car's earth (chassis), it may be as easy as adding a wire between
any of the lamp's earths and the chassis. Easy to try as a diagnostic
check using alligator clips or just holding the wires in place. If any
joy, you can solder or screw/clamp it permanently.
On Wed, 28 Nov 2012 08:58:02 -0500, email@example.com wrote:
Grab a test lead and clip it to the shell of the socket at one end
and a good ground at the other end. If that fixes it trace down the
ground or simply throw on a ground wire to a screw into the body. If
that doesn't fix it, it's not a ground problem, so keep looking.
If it's like my old Mercury Mystique it will be a bad connection
close to the brake switch for the brake lights. unless you have 2 bad
grounds or 2 bad bulbs, or both. Stranger things have happened.
At the second dealership I worked at after getting my mechanic's
licence the service manager and the apprentice spent over 3 hours
trying to figure out why none of the headlights worked on a Datsun
510. Because I had japanese vehicle and electrical experience they
kept asking me questions as I worked on another job. I answered every
question - (he never asked the right one) and when finished the job I
was working on I stuck a stick in the hornet's nest and told the
service manager it wasn't rocket science and should not have taken
more than half an hour to diagnose and fix.
He threw the keys at me and said "if you're so damned smart YOU fix
it." I called to the parts department for 2 high beam and 2 low beam
headlights - popped them in and everything worked.
First check all the fuses. Note some GM vehicles have a "Brake" AND a
"Stop" fuse. One is for the ABS brake system controller and the other is
for the tail lights! (Read all fuse names.)
Then there can be a wire or connector which has broken / come loose /
has a bad connection. But with cars, most of the wiring is "hidden" and
in taped up bundles. So you can't exactly go tracing wires to inspect
them and see where they go.
You can visually inspect wires around the brake switch above the brake
pedal. And in the rear of the vehicle.
If all the lights are on a "hatch back" which opens, then very likely a
lot of opening and closing of the rear door has worn out a wire. Like
bending a coat hanger back and forth - eventually it breaks.
Other than the above, you pretty much need a factory wiring diagram. And
then need to test at various connectors with a multimeter. The wiring
diagram shows WHERE various connectors are located. And WHICH
connections on a particular connection are for what - thus what to test.
They also say what wire colors are used for various things. And note
that some vehicle manufacturers will switch wire colors as the wire goes
from connector to connector! So it might start out blue at the brake
switch, then be green as it travels through the passenger area of the
vehicle, then switch to gray at the rear (those colors are not for any
specific vehicle). And they will change these wire colors from year to
year! (That is on other than Volvo vehicles - I don't know about Volvo.)
Thanks to all for your input. Here's what I found:
It is not the ground and it is not the fuse either. I triple checked
and the ground is fine on both tail (in the trunk) lights.
Like I said, the 93 240 has a third brake light located inside the
car, at the bottom of the rear window. And this light turns on when
the I press the brake pedal. That's how I know it is not the fuse as
removing the fuse disables this third light.
Now, I have listened carefully when I press on the brake pedal and I
can hear a 'click' coming from somewhere inside the center console. So
there must be a switch or relay in there. Can anyone confirm? I
would like to know before starting to take apart the center console.
Also, could this disable not only the brake lights but also the tail
lights too? Btw, the flasher at the rear are working on both sides.
And all the bulbs are fine.
Thanks again for your help.
Is your car a sedan or a wagon?
And are the brake lights on a trunk lid which opens or a rear door which
Can you follow the wire from that center light to where it connects with
the wires for the other brake lights? Do they all connect to the same
I would check that first!
Also automobile manufacturers can wire things any sort of way. There can
be two relays for the lights and separate wires run. Or two separate
fuses. Or all on one relay/fuse and all run via one wire to the back.
The brake switch could even switch both set of lights separately or
there even be two switches. Higher quality products have "back-up" dual
systems. Anyway a wiring diagram thing.
Also I assume you checked the bulbs? In *very* rare situations, you can
get both bulbs to burn out at the same time. Those typically have dual
elements. Anyway that is another thing you can check without a wiring
Check the bulbs and be SURE that they are good.
If this is a wagon, you probably have broken wires. Look up by the
a harness on both sides. Open the covering and you will find broken wires.
that, been there.
Pull the bad bulb relay. There is one someplace in the car, don't
Get the cover off of this device, and find the circuit board. Inspect all
that connect to the external pins. A common failure on these is cracked
Reflow the solder joints, or replace this device. Done that, been there.
only works on bulbs that have both left and right, such as headlights,
taillights, brake lights,
etc. because it compares the current from the left wire with that of the
Actually done very creatively. They wind a wire from the left circuit
around a reed
relay, and then wind a wire from the right circuit in the opposite
both lights work, the magnetic fields created by the currents flowing
'coils' around the reed relay cancel, and the relay doesn't close. If one
bulb is bad
the magnetic field from the good bulb is strong enough to close the reed
the bad bulb indicator on the dash lights up. The 'third' brake light (the
one that works
on your car), is NOT sensed by this device, that's why it still works. Done
Put a meter on the wire right at the taillight housing. Jam the brake
pedal down, or
have someone press it. Make SURE that you have or do not have voltage
rare to have a failure between the dash and the taillights unless you have
or rust issues.
I don't remember how the 240 does it, but on my 740s and 940s, the bulb
in a 'twistlock' socket that then 'twistlocks' into the circuit board on the
inside the trunk. The contact blades swipe a piece of circuit etch on the
board to make
contact. A common failure point on these cars. Done that, been there....
If a sedan, my bet is the bad bulb relay. If a wagon, my bet is the
harnesses at the
hinges or the bad bulb relay. Done that, been there on all counts.....
If you can't find the relay, let me know. I still have my Haynes book
for the 240
and I'll try to find it if you can't find the relay.
Good luck, and please let us know what fixed it.
Thanks Glenn for such an expansive reply. Sorry I didn't mention it
was a sedan. Also, I don't know if it means anything, but when I put
the car in reverse, the white lights in the tail lights are also not
I have the Haynes book for the 240 and I'll look for that relay.
It will take me a few days, top say the least, but I'll keep you
Thanks again for your help.
On Fri, 30 Nov 2012 23:15:05 -0500, firstname.lastname@example.org wrote:
Yep, the flashers are working fine.
Not sure what you mean by 'high level'. The bottom line is no tail
light at all except for the turn signals.
I guess I'll start by taking the tail lights out of and inspect them
Great that you have the Haynes. Go directly to the wiring diagrams.
Find your year or the newest one in the bunch. The brake lights, tail
and I think the directionals come from the bad light relay. The reverse
lights and the rear fog lights come directly from their respective control
So, hopefully this comes out considering the way my last post was
LIGHT CONDITION POWER SOURCE
brake lights - not working bad light relay
tail lights - not working bad light relay
reverse lights - not working transmission rev. switch
directionals - ???????? turn signal switch/flasher
flashers (hazards?) - working hazard switch/flasher
You may have several problems, or one problem in several places.
I hope you have a voltage/ohm meter for testing, otherwise, much
harder to fix.
Take the taillight assembly apart. Pull each bulb holder (one at a
they are different), and pull each bulb out. Make sure that all the
Do this before you disassemble the taillight assy. Look at the
Go to either taillight on the drawing. On all the wire lines, just before
taillight symbol, is a small circle on the wire with a number like 146/4.
is the connector that brings all the signals to the taillights. Take it off
taillight, or separate the two halves of the connector, so that the
is isolated. Now, figure out which wire is which from the schematic which
gives you a pin number and wire color. There should be very small numbers
on the connector, or use the color as a guide.
Put one meter probe to the car ground (bolt, etc.) and with all signals
enabled (turn signals on, backup lights on, taillights on, brakes on, rear
on. Is there approx. 12 volts at each connector pin for the function you
testing. If not, the source is the problem. If so, the problem is in the
Follow the signal path from source to destination.
Also, with everything off, find the ground wire which is W-SB or
Measure ohms from that wire to the car chassis ground and make sure you have
a ground path for all lights.
No matter which circuit, you need only 2 things getting to the bulb.
the signal source, and ground.
Corrosion in the power circuit has been an issue on my cars. For you,
or maybe all 240s have a fuse corrosion issue, I believe from water getting
fuseblock which is under the dash, where it can get wet. Pull each fuse,
sure all contacts are clean. Pull the battery ground if you are going to
hit them with
a wire brush please !! 8*)
Check that the connector to the taillight assembly is making contact.
that the bulbholder has good contact to the etch on the back of that
Make sure that the bulb has good contact to the bulbholder....... and so
OK, I'm tired of typing. Tell us what you find, everywhere. In detail.
with eliminating what isn't the problem.
Oh, did you find the bad bulb relay and open it up?
good luck, /glenn
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