Inconsistent Headlight Retract
Thread Starter
Instructor
Joined: May 2014
Posts: 107
Likes: 7
From: Los Angeles California
Inconsistent Headlight Retract
Hey Guys!
I just upgraded my headlights to new LED bulbs. They look great, except now for some reason the headlights do not always flip down when I turn the lights off! The behavior is not consistent.
Sometimes the headlights flip down like they should, other times they do not.
I noticed that when I flip the switch off for the headlamps, the light bulbs get a small flicker illumination while attempting to flip down.
Help!
Thanks!
I just upgraded my headlights to new LED bulbs. They look great, except now for some reason the headlights do not always flip down when I turn the lights off! The behavior is not consistent.
Sometimes the headlights flip down like they should, other times they do not.
I noticed that when I flip the switch off for the headlamps, the light bulbs get a small flicker illumination while attempting to flip down.
Help!
Thanks!
Thread Starter
Instructor
Joined: May 2014
Posts: 107
Likes: 7
From: Los Angeles California
This isn't really the solution I'm looking for, it defeats the point of my upgrading the low beams if I just leave the high beams on all the time...
I think there may be something wrong with the lights I got, and maybe need to return for a different set.
I think there may be something wrong with the lights I got, and maybe need to return for a different set.
Drifting
Joined: Nov 2016
Posts: 1,660
Likes: 365
From: SF Bay Area
Many threads on this issue. The reason is because LEDs do not behave like halogen bulbs in a circuit.
When the lights are turned off, the HCM "on" pin becomes grounded through the headlights. It is looking for either a maximum resistance or certain voltage before it drops the headlights. If the voltage/resistance is too high, which can be the case with LED bulbs due to how they behave at low voltages, the HCM thinks a bulb is out and keeps the headlights up. The remedy is typically having resistors in parallel with the bulbs, but that generates a lot of heat. One person has reported success with anti-flicker capacitors, but haven't heard back from others that said they would try it. Capacitors would be preferable to resistors in that they won't consume power like resistors.
When the lights are turned off, the HCM "on" pin becomes grounded through the headlights. It is looking for either a maximum resistance or certain voltage before it drops the headlights. If the voltage/resistance is too high, which can be the case with LED bulbs due to how they behave at low voltages, the HCM thinks a bulb is out and keeps the headlights up. The remedy is typically having resistors in parallel with the bulbs, but that generates a lot of heat. One person has reported success with anti-flicker capacitors, but haven't heard back from others that said they would try it. Capacitors would be preferable to resistors in that they won't consume power like resistors.
Melting Slicks
Joined: Oct 2002
Posts: 2,515
Likes: 441
From: Arizona
you don’t have to high beams on all the time. You just have to turn them on in order to close the lights. I’ve heard of this problem which is why I kept the stock halogen. As stated above I don’t think anyone has reported a permanent solution.
Thread Starter
Instructor
Joined: May 2014
Posts: 107
Likes: 7
From: Los Angeles California
This is annoying... I thought it would be a plug and play solution.
I'm not a stranger to hacking harnesses, but it doesn't seem like I would need to do that if there are easy solutions out there?
Something like this seems to fit the bill, no splicing needed.
I'm not a big fan of such a large resistor, the heat it must generate must be immense.
I found this plug and play capacitor harness
I'm a little concerned with it though because one of the reviewers reported it didn't help his LED light conversion for his C4. I don't know the detailed difference between C4 and C5 lights, but they are likely not that different
I'm not a stranger to hacking harnesses, but it doesn't seem like I would need to do that if there are easy solutions out there?
Something like this seems to fit the bill, no splicing needed.
I'm not a big fan of such a large resistor, the heat it must generate must be immense.
I found this plug and play capacitor harness
I'm a little concerned with it though because one of the reviewers reported it didn't help his LED light conversion for his C4. I don't know the detailed difference between C4 and C5 lights, but they are likely not that different
Last edited by Zoidman; Mar 4, 2019 at 08:07 PM.
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Drifting
Joined: Nov 2016
Posts: 1,660
Likes: 365
From: SF Bay Area
LEDs by their nature become an open circuit when voltage drops to a certain level. If the HCM doesn't detect low enough resistance/volts, it's not going to lower the lights. The capacitors might fool the HCM, it might not, YMMV. One member said it did on his C5. No other member reported success or failure.
Alternatively, you can get rid of the OEM HCM and build your own HCM that will close on demand. UM Rebel (I think) has a detailed writeup on how to do so.
Alternatively, you can get rid of the OEM HCM and build your own HCM that will close on demand. UM Rebel (I think) has a detailed writeup on how to do so.
Thread Starter
Instructor
Joined: May 2014
Posts: 107
Likes: 7
From: Los Angeles California
LED's generally become closed circuits, limiting the flow of current, once the voltage falls below the activation voltage of the diode. If the voltage is above the diodes activation voltage they allow current to flow through them, in this case emitting light as a by product.
https://www3.nd.edu/~lemmon/courses/...ab1/node6.html
I'm not sure if the capacitors make sense to fix this situation. Capacitors sort of work like a mini battery continue to provide power to the LED's for a very brief amount of time until the capacitor is depleted. This is great when you have dirty power delivery to LED's because it can debounce the power spikes or dips providing a smoother output to the LED's thus eliminating flickering as advertised. I don't think it would change much of the electrical characteristics from the HCM point of view though.
https://www3.nd.edu/~lemmon/courses/...ab1/node6.html
I'm not sure if the capacitors make sense to fix this situation. Capacitors sort of work like a mini battery continue to provide power to the LED's for a very brief amount of time until the capacitor is depleted. This is great when you have dirty power delivery to LED's because it can debounce the power spikes or dips providing a smoother output to the LED's thus eliminating flickering as advertised. I don't think it would change much of the electrical characteristics from the HCM point of view though.
Advanced
Joined: Feb 2018
Posts: 90
Likes: 10
LED's have low resistance not high. Adding resistors ups the load on the circuit allowing the command to close to function. There's nothing wrong with your LED bulbs. Just simply add resistors or as stated above, turn on your high beams ( more lights on, more resistance) to lower them when you shut the car off.
Drifting
Joined: Nov 2016
Posts: 1,660
Likes: 365
From: SF Bay Area
LED's generally become closed circuits, limiting the flow of current, once the voltage falls below the activation voltage of the diode. If the voltage is above the diodes activation voltage they allow current to flow through them, in this case emitting light as a by product.
https://www3.nd.edu/~lemmon/courses/...ab1/node6.html
I'm not sure if the capacitors make sense to fix this situation. Capacitors sort of work like a mini battery continue to provide power to the LED's for a very brief amount of time until the capacitor is depleted. This is great when you have dirty power delivery to LED's because it can debounce the power spikes or dips providing a smoother output to the LED's thus eliminating flickering as advertised. I don't think it would change much of the electrical characteristics from the HCM point of view though.
https://www3.nd.edu/~lemmon/courses/...ab1/node6.html
I'm not sure if the capacitors make sense to fix this situation. Capacitors sort of work like a mini battery continue to provide power to the LED's for a very brief amount of time until the capacitor is depleted. This is great when you have dirty power delivery to LED's because it can debounce the power spikes or dips providing a smoother output to the LED's thus eliminating flickering as advertised. I don't think it would change much of the electrical characteristics from the HCM point of view though.
LED's have low resistance not high. Adding resistors ups the load on the circuit allowing the command to close to function. There's nothing wrong with your LED bulbs. Just simply add resistors or as stated above, turn on your high beams ( more lights on, more resistance) to lower them when you shut the car off.
Putting resistors (and additional bulbs) in parallel with the bulb does not increase overall resistance, it decreases it. The HCM is looking for low resistance (or low voltage), not high resistance.
Thread Starter
Instructor
Joined: May 2014
Posts: 107
Likes: 7
From: Los Angeles California
I ordered the capacitor kit and can report that it did not fix the problem. As a matter of fact, once installed the headlights did not turn on at all.
The resistor kit on the other hand did solve the headlight problems, and they now pop up and down correctly.
Unfortunately, while doing all this my IPC lights are now out... The warning indicators come up, but there is no back-lighting. Is this somehow related to installing the LED headlamps? Could this have fried the multi-function light switch stalk?
The resistor kit on the other hand did solve the headlight problems, and they now pop up and down correctly.
Unfortunately, while doing all this my IPC lights are now out... The warning indicators come up, but there is no back-lighting. Is this somehow related to installing the LED headlamps? Could this have fried the multi-function light switch stalk?
Thread Starter
Instructor
Joined: May 2014
Posts: 107
Likes: 7
From: Los Angeles California
A lot of people report problems with the IPC lights and the turn signal stock, which is also used to turn on/off the headlights
https://www.corvetteforum.com/forums...-a-how-to.html
https://www.corvetteforum.com/forums...-a-how-to.html
Instructor
Joined: Jul 2015
Posts: 232
Likes: 52
From: Miami FL
Hello did you use these resistors that you described earlier?
Because I just bought these and sadly must report that the headlight doors do not naturally close with these installed:
If you are reporting success with the O-NEX brand of resistors, then I will return mine and purchase those, and in the mean time, activate the high beams in order to close the headlight doors.
Because I just bought these and sadly must report that the headlight doors do not naturally close with these installed:
If you are reporting success with the O-NEX brand of resistors, then I will return mine and purchase those, and in the mean time, activate the high beams in order to close the headlight doors.
Melting Slicks
Joined: Oct 2002
Posts: 2,515
Likes: 441
From: Arizona
Looks like this thread the resistors didn’t work.
https://www.corvetteforum.com/forums...ose-doors.html
https://www.corvetteforum.com/forums...ose-doors.html