need electrical help..

[bigchillcar]

1974..driver's side taillamp. sigh..seems i've been messing with this corner for years now. here's the problem: headlights on? my left rear marker light works. hit the brake? instead of the second filament illuminating (2-filament bulb remember), they're both out..no light at all. this only happens at night when i have my headlights on. during the day the brakelight comes on as it should.

biggest fear with this problem is getting 'pulled over' on some late friday or saturday night. i thought it was a matter of the bulb just being loose in the socket and have tried myriad ways of making it a more solid fit. anyone else see this before? how'd you fix it?
ryan

[RoninLB]

Sounds like typical circuit weak ground scenario.

maybe try using a wire jumper attached to a ground then probe around the bulb case when the lights are in this "out" mode. I find that a quick yes/no test.

[Rex Walter]

Ryan,

I had a similar problem with that corner on my 75. The lights would work fine with the light housing pulled out, but when you slid the housing back into position, one of the contacts touched the fender or bumper. That said, RoninLB is probably right, bad ground causes lots of weird stuff.

Rex

[bigchillcar]

thanks, ron..good idea.
rex..yep, this sounds all too familiar..it's 'fixed' as long as the whole ggoddamn assembly is hangin' out..
ryan

[Jim Sims]

Make sure you have the correct "two contact" base bulbs in ALL (front and rear) two contact base sockets and that they are rotated correctly and that the two base contacts are not shorted together by corrosion (silicone dielectric grease is helpful in preventing this) either in the sockets or on the bulb bases.

[bigchillcar]

hi jim,
from memory, i think i'm using '1157' for the bulb. dielectric grease used on all of them. believe it or not, the last effort at solving the problem had me taking elmers wood glue and placing a small bead around the bulb's barrel, just near the glass. my thinking was that this would 'hold it' or at least dry and take up the 'movable gap'..and when it would be time to replace, wood glue would be easy to break free. it was working when i put it in..i tested it with headlamps on..but a week later (last night) i had someone check back there and no go..
ryan

[Jim Sims]

To improve fit, some build up the bulb by melting on bits on solder at the correct places: groove lugs on the side of the bulb base and on each base contact.

[RoninLB]

I had to open up a front parking light socket because the spring action wasn't functioning with enough "spring". I had to mox nix the spring holder assembly to get it working again.

[bigchillcar]

i'd heard that some used solder. just dabs of it on the barrel to improve tightness of the fit, then? as for the 'spring', the base of my socket had 'popped out' so many times that i finally jb welded it on.
ryan

[RoninLB]

My prob was the delicate spring and contacts assembly itself. The contacts slide up/down in this housing. The housing was falling apart and couldn't hold the spring and sliding contacts properly. I used one of those fine files that you see around that comes in a packet of about 15 8" long thin files in a pack. I filed groves in the spring holder and then some small dia .024 safety wire to hold it cylindrical.

I found out the unit is expensive and frail so a used one is a waste of time imo.

I should have taken pics but I was distracted by the thought "what a piece of crap".

This spring prob would not cause both bulbs to go out. A common ground is more likely for a 1st attack and the ground jumper is a quick test.

You now have 3 guys offering info for you to start having a happy Saturday..

party hearty

[bigchillcar]

You now have 3 guys offering info for you to start having a happy Saturday..

thanks, ron..sigh..i'd almost prefer a root canal than to pulling the goddamn assembly back out. i wonder if your assembly is different from mine, though. mine has no springs in the base of the barrel..just two metal prongs that i had to 'bend up' a little more to make for stronger contact. the prongs are 'rooted' in a kind of coated, hard cardboard material (forget what that stuff is called..found in computers and where all the resistors, capacitors and all the other little electrical doodads go). anyway, no spring..
ryan

[RoninLB]

I mentioned that I was working on a front parking lamp assembly.

I'm still guessing it's a ground.

[FrayAdjacent911]

Originally posted by bigchillcar
thanks, ron..sigh..i'd almost prefer a root canal than to pulling the goddamn assembly back out. i wonder if your assembly is different from mine, though. mine has no springs in the base of the barrel..just two metal prongs that i had to 'bend up' a little more to make for stronger contact. the prongs are 'rooted' in a kind of coated, hard cardboard material (forget what that stuff is called..found in computers and where all the resistors, capacitors and all the other little electrical doodads go). anyway, no spring..
ryan

The contacts on the PCB like board are kinda 'sprung', and use spring tension to maintain contact with the bulb.

I'd definitely check that out, make sure it's clean, make sure the board is not loose. Stinky had one that cracked a little and didn't want to stay in. Some epoxy fixed it's wagon!

Also BE CAREFUL when sticking the bulb in. Maybe you, or a PO tried to shove it in backwards, putting too much stress on the board or contacts. Note that the pins on the bulb are staggered... it CAN be forced in the wrong way! (You can tell people do that when you see cars at night when one tail light is a lot brighter than the other and doesn't change when they hit the brakes)

[bigchillcar]

matt..i'm thinking i'm orienting the bulbs correctly, but i suppose anything is possible. i hit the big '40' this year and may not be quite as 'sharp as a tack' anymore.. i'll check both sides for that.
ryan