M
[email protected]
- Jan 1, 1970
- 0
Hello all!
A couple of months ago I helped a friend change one of the stop/tail
lamps on his '98 Chevy Malibu. It was a 3057 lamp - the "wedge base"
type where the base is rather flat, instead of the more traditional
round brass base. Anyway, I got it out of the socket pretty easily,
and noticed that the bulb didn't have any black or silver spots on it.
I held it up to the daylight and saw that the filaments looked OK -
tapping the bulb didn't result in loose filament ends flopping around.
Finally, I looked at the base and saw the problem.
On this particular lamp, there is a plastic piece on the base that the
lead wires from the filaments are laid on top of. Some flat springs in
the socket contact these wires when the lamp is installed. Apparently,
there was a poor connection at one of the contacts for the brighter
filament that caused the lead wire to heat up. The lead wire was
unbroken, but the plastic around it was pitted and melted. The wire had
sunk into the plastic, visibly lower than the other wires on the base.
After it sunk long enough, it no longer made reliable contact with the
contact in the socket. I applied 12 V to the lead wires and the bright
filament lit right up.
I couldn't see very well into the socket to see what might have been
damaged there, but I could see some markings on the affected contact. I
cleaned the contact as best I could with an emery board (it was handy),
blew out the dust, and bent the contacts a little more towards the center
so they would press harder on the lamp base. I then installed a
replacement lamp, and it's been working fine for a couple of months now.
I don't remember exactly the brand of the failed bulb. I know the tail
light assembly was made by Britax. I may still have the bulb around
here somewhere.
I thought this was kind of an interesting failure mode. A few years
ago, when these wedge base lamps started appearing at the auto parts
store, it seems to me that most of them had a glass base. The bulb was
simply extended down and pressed flat to form the base - there was still
a plastic ring around it to locate the lamp in the socket, and to stop
the wrong type of lamp being put in the socket, but the lead wires were
on top of pressed glass. All of these lamps that I have seen lately are
the kind where the base is mostly plastic, and the lead wires lie on top
of plastic. This style is probably easier or cheaper to manufacture,
but I think the glass base would have done better in this situation. On
the other hand, the heat generated might have tended to melt the plastic
socket instead, which would be much more expensive to replace. The
socket was part of a molded assembly with three other sockets; I'd
rather buy a $2 bulb than what is probably a $50 part at the dealer.
Matt Roberds
A couple of months ago I helped a friend change one of the stop/tail
lamps on his '98 Chevy Malibu. It was a 3057 lamp - the "wedge base"
type where the base is rather flat, instead of the more traditional
round brass base. Anyway, I got it out of the socket pretty easily,
and noticed that the bulb didn't have any black or silver spots on it.
I held it up to the daylight and saw that the filaments looked OK -
tapping the bulb didn't result in loose filament ends flopping around.
Finally, I looked at the base and saw the problem.
On this particular lamp, there is a plastic piece on the base that the
lead wires from the filaments are laid on top of. Some flat springs in
the socket contact these wires when the lamp is installed. Apparently,
there was a poor connection at one of the contacts for the brighter
filament that caused the lead wire to heat up. The lead wire was
unbroken, but the plastic around it was pitted and melted. The wire had
sunk into the plastic, visibly lower than the other wires on the base.
After it sunk long enough, it no longer made reliable contact with the
contact in the socket. I applied 12 V to the lead wires and the bright
filament lit right up.
I couldn't see very well into the socket to see what might have been
damaged there, but I could see some markings on the affected contact. I
cleaned the contact as best I could with an emery board (it was handy),
blew out the dust, and bent the contacts a little more towards the center
so they would press harder on the lamp base. I then installed a
replacement lamp, and it's been working fine for a couple of months now.
I don't remember exactly the brand of the failed bulb. I know the tail
light assembly was made by Britax. I may still have the bulb around
here somewhere.
I thought this was kind of an interesting failure mode. A few years
ago, when these wedge base lamps started appearing at the auto parts
store, it seems to me that most of them had a glass base. The bulb was
simply extended down and pressed flat to form the base - there was still
a plastic ring around it to locate the lamp in the socket, and to stop
the wrong type of lamp being put in the socket, but the lead wires were
on top of pressed glass. All of these lamps that I have seen lately are
the kind where the base is mostly plastic, and the lead wires lie on top
of plastic. This style is probably easier or cheaper to manufacture,
but I think the glass base would have done better in this situation. On
the other hand, the heat generated might have tended to melt the plastic
socket instead, which would be much more expensive to replace. The
socket was part of a molded assembly with three other sockets; I'd
rather buy a $2 bulb than what is probably a $50 part at the dealer.
Matt Roberds