Hey y’all,. Been searching and fiddling for about a week now and can’t get the brake lights to work. For all testing I have the brake switch jumped with a piece of wire to eliminate the switch as a cause. And to keep the line hot while I messed around. The car has:
-new turn signal switch from wccc
-new sequential box from wccc
-checked power to the brake switch plug and recieves a solid 12 volts.
-Turn signals AND hazards work.
-checked green and white wire all the way to trunk for power and has 12 volts right before it hits box.
Light bulbs need power and ground to operate. You are certain that voltage is present at the plug. So jumper the plug to simulate the switch being “ON”, then measure for voltage at the tail lamp bulbs.
If there is no voltage then you have something unplugged or there is a broken wire.
If there is voltage then you have a ground wire disconnected or a broken wire.
Yeah my lil meter said 12.2 at the green and red wire going to switch. I do have the switch jumped to simulate on to make things easier. Does the brake signal travel thru the sequential unit? The only ground I see is on the trunk latch
Isn’t there a relay mounted inside the driver side quarter? I discovered that thing when I had a short in a bulb, and it kept kicking the circuit off, but I can’t remember if it was part of the parking lights circuit or the brake lights circuit.
So I’ve heard. I’ve been following the wires. I get a 12 volt signal all the way the trunk into the solid state sequential box. Past that idk where to check
Hmmm, Ive been reading your post and your posts on the other thread. Your problem is intriguing and may be a simple fix.
As you stated, you are getting 12V on the input brake signal to the sequential unit but still no brake lights.
I know I know, but stay with me here for a minute. The brake lights are electrically disconnected via the k8/k9 relay when the turn signal is in left or right mode ( allows the turn signal to to operate on the one side and the brake light to illuminate on the other when the brakes are applied). Also, when the emergency flashers are enabled, the turn signal switch disconnects the brake lights in the k8/k9 relay.
You can test this by probing the circuits 440 (white) and 441 (violet) circuits in the d-4 square connectors. (Note the circuits are in two separate connectors, circuit 440 is in the white connector and 441 is in the red connector). With the turn signal switch in the center position and the flasher switch off, there should be NO power on either of these two wires. If you have power here, then it indicates to me that your turn signal switch is improperly wired.
Hopefully your fix is as simple as pulling the emergency flasher switch to the off position.
Give this a shot and let me know if you need any additional information.
Alright so I’ll check for voltage at the wire going into the socket. Is it the black or colored ones going to the socket. And is the only ground i need to check is the contact between the housing the bulb holder
The tail lamp housings do not provide a ground. The socket gets ground from the wire which is attached with a self tapping screw and a star washer at the trunk latch bracket next to the fuel filler pipe. If the star washer is missing then you don’t have a ground.
I do not have the schematic handy but it is the contact that does not have power when the headlamp switch is on or parking lamps on and brake lights off.
First: What year is your Cougar? I didn’t see a year stated in your previous posts.
Assuming it is a 1969-70, the symptoms indicate a bad turn signal switch or connector.
The brake light switch input pin (green) could be fried.
On a 1969-70, the inside lights (first in sequence) are connected directly to the switch,
so if you do not have any brake lights, the switch is not providing brake light power.
The 18 ga green wire to the trunk is just a signal wire to tell the control unit if the brake has been applied.
On later control units this signal is ignored and is not used. The brake/turn signal power runs
to the trunk on the green/orange and orange/blue wires.