Break Lights out 71 2800CS

[audiokat]

Seem to have lost my break lights. Interestingly, rear blinkers still work. I just installed a new stereo and a lot of my wires ran along side the harness on their way to the trunk. Fuse is fine presuming after 50 years it's still on the main fuse panel and I can't find any damage or nicks or anything to the harness.

I've read that ground might likely be the issue. Does anyone know which wires coming out of the back of the tail lights would be ground so I can jumper to chasis to see if that helps.

Or have any other great ideas?

 

[Arde]

I think that the ground is common to all rear lights, so if rear blinkers work, the ground attachment should be fine. I would remove the brake light bulbs and measure continuity between the bulb socket and ground to be sure.

Then there is the brake light switch, you can measure continuity across the switch with the ignition key out and pressing the pedal. If that works, ignition switch on and measure voltage at both brake switch contacts pressing the brake pedal.
If no voltage, then go to the fuse, but if the horn works the fuse should be fine.

I am sure it will be easy, in the meantime drive without braking, it is a useful skill.

 

[audiokat]

So with depressed I should see continuity across both terminals of the switch?

 

[Arde]

So with depressed I should see continuity across both terminals of the switch?

Yes

 

[HB Chris]

Many times it is the bulbs and removing them and cleaning them can do wonders. Ground is always a brown wire but as Arde says you must have ground already. The brown wire is grounded between spare and gas tank right under trunk lock area.

 

[audiokat]

Yea checked horn and it's good. Would one bad bulb cause them all not to work?

Arde got some magic trick to get to that switch without removing the under dash?

 

[audiokat]

All sockets pass continuity besides the socket with Green/Red. IN looking at a 74 wiring diagram that appears to be the break light.

 

[HB Chris]

Clean the spade terminals at the lamp housing and lightly crimp the female spades.

 

[audiokat]

So I removed the panel and ran a jumper wire and got continuity on both ends of the cable (lamp and switch), then got continuity connecting both side of the switch. Then magically after hooking the switch back up the brake lights started working again. Recently I had to re-attach my clutch pedal so that more likely is when I lost it.

However this did lead me to discover that my lamp housing on my passenger side (US) appears to be bad. My right brake light is intermittent working only as I wiggle the housing. I even ran a fresh cable form left light to right and still no go unless I wiggled the lamp side spade.


Any experience replacing one of these?

 

[wkohler]

If you look at the housing you’ll note that the ground path only connects to one half of the lamp housing (the inner two sockets). The brass strip on the trunk side of the housing connects the two halves together. If you notice how that strip is attached, you can see how there can be a failure. Cleanest solution is to connect the two halves together inside the lamp housing essentially eliminating the reliance on the brass strip.

 

[audiokat]

Update for future searches. Problem fixed now. The spade connectors are almost like a Z with the connector side on the outside of housing and the bulb terminal side on the inside. Then plastic housing had worn down causing the spring fit of the bulb to just push the terminal away from the bulb. I did small layers of crazy glue over two hrs to seal the connector back in the housing. Not sure how to crazy glue will hold up in the heat but for now the fix is working.

 

[skk]

cyanoacrylate won't last. remove it all, rough the surfaces with sandpaper, and try something more structural with more general
bonding properties. I've had good results on various plastic/metal bondings with 2 part epoxies, jb weld, and RTV (room temperature vulcanization)