Glovebox LED Light Weirdness
#1
Rennlist Member
Thread Starter
Glovebox LED Light Weirdness
So I upgraded my two interior, trunk, engine compartment, glovebox and license plate lights with the LED kit from Suncoast. Very nice upgrade and they all function fine. Polarity mattered for all except the glovebox LED which worked in either pole position.
When done I pulled the fuse that controls all these bulb locations because the car is in winter storage. I also pull the clock fuse so it doesn’t run for six months needlessly. Have done this for 17 years.
The weird thing is thst when when I went to close the glovebox door with the fuse pulled - so no power to that circuit - the new glovebox LED bulb will light very dimly, like at 1/20th normal. It only lights when the door is nearly closed and I think it stays on when fully shut.
With the circut fuse installed the LED bulb acts normally and shuts off with the door. I reversed the LED and the same weird dim light. I installed the old incandescent bulb and no issue.
Any ideas? It’s not going to matter as there’s no current draw and the car lives on a maintainer anyway. Or I can just install the old incandescent bulb.
Another chapter in 993 idiosyncratic behavior. A bottle of good wine to the RL genius that figures this one out. Apologies for the long post and dull subject.
When done I pulled the fuse that controls all these bulb locations because the car is in winter storage. I also pull the clock fuse so it doesn’t run for six months needlessly. Have done this for 17 years.
The weird thing is thst when when I went to close the glovebox door with the fuse pulled - so no power to that circuit - the new glovebox LED bulb will light very dimly, like at 1/20th normal. It only lights when the door is nearly closed and I think it stays on when fully shut.
With the circut fuse installed the LED bulb acts normally and shuts off with the door. I reversed the LED and the same weird dim light. I installed the old incandescent bulb and no issue.
Any ideas? It’s not going to matter as there’s no current draw and the car lives on a maintainer anyway. Or I can just install the old incandescent bulb.
Another chapter in 993 idiosyncratic behavior. A bottle of good wine to the RL genius that figures this one out. Apologies for the long post and dull subject.
#5
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Thread Starter
#6
Banned
Red, Sonoma or Napa please. Actually red or white is a good question as white LED's use phosphor that is in fact phosphorescent, so they can glow for some time before going out. Have you checked after a day?
#7
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Thread Starter
Good advice I will check the hibernating 993 tomorrow. Thank you.
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#8
Rennlist Member
I'm no EE but it may be a capacitive coupling issue, so perhaps the lines to the lamp are hot, meaning that the switch is downstream from there. If you pull the assembly and find 12v on the line even when not lit, that would explain it. If so, there's no feasible solution, but who cares if it's really pulling miniscule current.
If im correct, that seems like odd wiring by Porsche. I'd expect the switch to be upstream of the lamp so that it's not always at 12V, especially because the lamp socket is bare, unprotected. But what do I know.
p.s. If I'm correct, the incandescent bulb is pulling the same minimal current as your barely-lit LED bulb. The difference is that a tiny current will actually barely light an LED. Of course, you could measure all that to confirm.
If im correct, that seems like odd wiring by Porsche. I'd expect the switch to be upstream of the lamp so that it's not always at 12V, especially because the lamp socket is bare, unprotected. But what do I know.
p.s. If I'm correct, the incandescent bulb is pulling the same minimal current as your barely-lit LED bulb. The difference is that a tiny current will actually barely light an LED. Of course, you could measure all that to confirm.
Last edited by TheOtherEric; 03-15-2019 at 12:25 AM.
#11
Rennlist Member
The glove box light light switch is connected to the alarm unit, and a small current is put on the circuit to detect the opening of the glovebox. This is where the current comes from that lights up your LED bulb.
To solve this, reinstall the incandescent light bulb, use a polarized LED light bulb, or connect a diode in series of the light bulb, cathode to glove box switch.
Cheers,
Tore
To solve this, reinstall the incandescent light bulb, use a polarized LED light bulb, or connect a diode in series of the light bulb, cathode to glove box switch.
Cheers,
Tore
#12
Rennlist Member
The glove box light light switch is connected to the alarm unit, and a small current is put on the circuit to detect the opening of the glovebox. This is where the current comes from that lights up your LED bulb.
To solve this, reinstall the incandescent light bulb, use a polarized LED light bulb, or connect a diode in series of the light bulb, cathode to glove box switch.
Cheers,
Tore
To solve this, reinstall the incandescent light bulb, use a polarized LED light bulb, or connect a diode in series of the light bulb, cathode to glove box switch.
Cheers,
Tore
#13
Rennlist Member
The glove box light light switch is connected to the alarm unit, and a small current is put on the circuit to detect the opening of the glovebox. This is where the current comes from that lights up your LED bulb.
To solve this, reinstall the incandescent light bulb, use a polarized LED light bulb, or connect a diode in series of the light bulb, cathode to glove box switch.
Cheers,
Tore
To solve this, reinstall the incandescent light bulb, use a polarized LED light bulb, or connect a diode in series of the light bulb, cathode to glove box switch.
Cheers,
Tore
And why would reinstalling the incandescent bulb solve this? Granted it won’t be visibly lit, but won’t it still draw the same current? If so, I wouldn’t consider that a solution to any real issue. A dome light is one thing, but a dim glove box bulb is never seen.
#14
Rennlist Member
I guess the voltage would be close to +12V without any load. However, this is applied through a resistor, and will fall to a very low value once loaded. This low current is not sufficient to light a filament bulb.
Looking from a low current perspective, the node of the bulb that normally is +12V is to be considered grounded through all the other filament lamps on this circuit.
Since the used LED is bidirectional (has an internal diode bridge or similar that makes it work in either polarity) the LED lights up due to the reversed current when glove box is closed and alarm on.
Cheers,
Tore
Looking from a low current perspective, the node of the bulb that normally is +12V is to be considered grounded through all the other filament lamps on this circuit.
Since the used LED is bidirectional (has an internal diode bridge or similar that makes it work in either polarity) the LED lights up due to the reversed current when glove box is closed and alarm on.
Cheers,
Tore
#15
Rennlist Member
Thread Starter
Tore, thanks for the info. So I guess since the incandescent bulb ihas been drawing a minimal current for all these years there’s no harm in leaving the LED bulb in place? I’ve checked this issue with the alarm disarmed of course.