Turn signal light dim
#1
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Turn signal light dim
Hey, I have a problem with the turn signal light in the instrument cluster being dim, really dim, when using the turn signal, either direction. No problem at all when turning on the hazard lights. All the external lights work just fine.
I have replaced all the bulbs with LEDs last year, but I don't believe that has anything to do with it - it worked fine all year. This year, occasionally the first blink is at the normal brightness, then it just remains dark, or blinks incredibly dimly. Again, with the hazards on it works perfectly.
I've tried replacing the blinker relay, cleaned all grounds and contacts, and replaced the hazard switch - the wiring diagram indicated that power to the blinker light is fed through the hazard switch.
Does anyone have an idea where the culprit might be? The wiring diagram is incredibly difficult to read through, and my next plan is to replace the turn signal module on the steering column.
This is an '84 928S.
Thanks.
I have replaced all the bulbs with LEDs last year, but I don't believe that has anything to do with it - it worked fine all year. This year, occasionally the first blink is at the normal brightness, then it just remains dark, or blinks incredibly dimly. Again, with the hazards on it works perfectly.
I've tried replacing the blinker relay, cleaned all grounds and contacts, and replaced the hazard switch - the wiring diagram indicated that power to the blinker light is fed through the hazard switch.
Does anyone have an idea where the culprit might be? The wiring diagram is incredibly difficult to read through, and my next plan is to replace the turn signal module on the steering column.
This is an '84 928S.
Thanks.
#2
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Stop replacing things and start diagnosing things...
Figure out where the voltage drops and why its different between hazard and turn signals...
I'd suspect your LED installation - revert to stock for testing?
Alan
Figure out where the voltage drops and why its different between hazard and turn signals...
I'd suspect your LED installation - revert to stock for testing?
Alan
#3
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From an e-mail exchange that I had with somebody else about this issue almost two years ago:
And later...
The (relatively ) short answer to your question is that you can add some load resistors and it'll almost certainly fix the problem you're describing. You don't need to do all four corners; I'm using load resistors on my rear turn signals only (they're easy to affix the the rear of the housing) and don't have any problems. IIRC (unfortunately, I don't believe I kept good records when I did this years ago), I actually added them to solve another problem (I think I was dealing with some weird interactions between different types of front and rear turn signals at the time; I think those problems were due to older LEDs that didn't have reverse voltage protection diodes in them). Anyway, I have no such problems with my turn signal indicator, and it's probably due to the presence of the load resistors and/or the fact that I'm running LEDs in my instrument cluster (which requires very little current to illuminate).
The long answer is to understand why this happens. Have you ever noticed that the turn signal indicator blinks out of phase with the turn signals themselves? (i.e., if you've turned on a turn signal or hazard lights, the indicator is on when the turn signal(s) are off and vice versa)
That's because 3-terminal flasher relays are wired something like this (the 928 is more complicated, but the operation of the turn signal indicator with respect to the relay is pretty much the same).
The main thing to notice (if you can read schematics) is that when the turn signal lever is switched on (either direction), the indicator light will be off when the relay closes (and the turn signal lights turn on), but it should turn on when the relay opens because the indicator light still has 12 V connected to one side, but the other side is then grounded through the turn signal lights, which (in their original incandescent form) are much lower resistance than the indicator bulb. So... raise the resistance (and the LEDs are effectively much higher resistance than the original incandescents), and... indicator bulb no longer has a good low-resistance path to ground. QED
There are probably other ways to solve this problem (e.g., reworking the way the indicator light works), but it probably is most expedient to just solve it with load resistors.
I'd suggest experimenting with the highest value resistors you can that get the job done. I can't tell you what values I used (I'm at work and my car is at home), but 25 Ω load resistors and 6 Ω load resistors are quite common. Remember: the lower the resistance, the more current the circuit will draw and waste in the form of dissipated heat.
The long answer is to understand why this happens. Have you ever noticed that the turn signal indicator blinks out of phase with the turn signals themselves? (i.e., if you've turned on a turn signal or hazard lights, the indicator is on when the turn signal(s) are off and vice versa)
That's because 3-terminal flasher relays are wired something like this (the 928 is more complicated, but the operation of the turn signal indicator with respect to the relay is pretty much the same).
The main thing to notice (if you can read schematics) is that when the turn signal lever is switched on (either direction), the indicator light will be off when the relay closes (and the turn signal lights turn on), but it should turn on when the relay opens because the indicator light still has 12 V connected to one side, but the other side is then grounded through the turn signal lights, which (in their original incandescent form) are much lower resistance than the indicator bulb. So... raise the resistance (and the LEDs are effectively much higher resistance than the original incandescents), and... indicator bulb no longer has a good low-resistance path to ground. QED
There are probably other ways to solve this problem (e.g., reworking the way the indicator light works), but it probably is most expedient to just solve it with load resistors.
I'd suggest experimenting with the highest value resistors you can that get the job done. I can't tell you what values I used (I'm at work and my car is at home), but 25 Ω load resistors and 6 Ω load resistors are quite common. Remember: the lower the resistance, the more current the circuit will draw and waste in the form of dissipated heat.
And later...
Originally Posted by Ed Scherer
I just pulled my right rear tail light assembly. It had a Super Bright LEDs RL-2525 (25 Ω) ohm resistor between one of the grounds (brown wire) and the blue wire. I didn't pull the left side, but the load resistor there would be connected between a ground (brown wire) and whatever non-brown colored wire goes to the turn signal socket.
And have you replaced the flasher relay? IIRC, I'm using a Super Bright LEDs CF13GL-02.
[...]
The only other possibility that comes to mind is that that maybe my LEDs are different; I need to check both front and rear bulbs and see exactly what I'm running right now (I've changed LED models a few times for various reasons).
And have you replaced the flasher relay? IIRC, I'm using a Super Bright LEDs CF13GL-02.
[...]
The only other possibility that comes to mind is that that maybe my LEDs are different; I need to check both front and rear bulbs and see exactly what I'm running right now (I've changed LED models a few times for various reasons).
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Are you saying that you have a 25 Ω resistor in parallel with the turn signal LED, between power and ground, one on each side? I can give that a try, although I think I'll add the resistor to the side marker lights instead of the tail lights - its much easier to pull them. Come to think of it, the side markers were the last external bulbs I replaced with LEDs, and that was right before I put the car in storage. The resistance of the bulbs may have been what was making it work, and when I swapped them I never noticed the turn signal indicator stopped working.
Thanks for the reply! I've read that adding resistors is necessary when used with a standard blinker relay, but I replaced it with a superbright LED blinker and didn't realize the resistors were still necessary.
Oh, and the dimmer module I bought from you works fantastic!
Thanks for the reply! I've read that adding resistors is necessary when used with a standard blinker relay, but I replaced it with a superbright LED blinker and didn't realize the resistors were still necessary.
Oh, and the dimmer module I bought from you works fantastic!
#6
Hey All:
I never saw a resolution to this issue, but I literally have the same problem after I just installed my LED's from superbright. I have resistors on all of the led turn signals and swapped the relay. All are working, but the rears are very dim. I'm going to start by checking the voltage. I'll keep you all posted.
I never saw a resolution to this issue, but I literally have the same problem after I just installed my LED's from superbright. I have resistors on all of the led turn signals and swapped the relay. All are working, but the rears are very dim. I'm going to start by checking the voltage. I'll keep you all posted.
#7
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Hey All:
I never saw a resolution to this issue, but I literally have the same problem after I just installed my LED's from superbright. I have resistors on all of the led turn signals and swapped the relay. All are working, but the rears are very dim. I'm going to start by checking the voltage. I'll keep you all posted.
I never saw a resolution to this issue, but I literally have the same problem after I just installed my LED's from superbright. I have resistors on all of the led turn signals and swapped the relay. All are working, but the rears are very dim. I'm going to start by checking the voltage. I'll keep you all posted.
Alan