| Both turn signal indicators on with head/parking lights [message #91677] |
Mon, 12 July 2010 16:19  |
Mike O'Connell
Messages: 53
Registered: November 2008
Location: Deerfield MA
Karma: 0
|
Member |
|
|
I have built my own dash so I may have brought this problem on myself, but the turn signals indicators both come on when I turn in the headlights. My turn signals works fine otherwise. I replaced the front turn signal/parking lights with oval LED lights found on many tractor trailer rigs, except they are amber.
Is there something in the way the turn signals are wired that warn the driver they have a lamp out and I have inadvertently triggered by putting in LEDs?
If so is there a fix?
A resistor or something?
Mike O'Connell
Deerfield, MA
'75 Eleganza
|
|
|
|
| Re: Both turn signal indicators on with head/parking lights [message #91682 is a reply to message #91677] |
Mon, 12 July 2010 16:41  |
Craig Lechowicz
Messages: 541
Registered: October 2006
Location: Waterford, MI
Karma: 0
|
Senior Member |
|
|
| Mike O'Connell wrote on Mon, 12 July 2010 17:19 |
I have built my own dash so I may have brought this problem on myself, but the turn signals indicators both come on when I turn in the headlights. My turn signals works fine otherwise. I replaced the front turn signal/parking lights with oval LED lights found on many tractor trailer rigs, except they are amber.
Is there something in the way the turn signals are wired that warn the driver they have a lamp out and I have inadvertently triggered by putting in LEDs?
If so is there a fix?
A resistor or something?
|
Mike,
Not the electrical expert here, but I don't think there is anything inherent in LED's that would make the dash turn signal indicator lights (I think that is what you mean, or do you mean the LED's themselves?) come on. Either way around, the low power draw of LED's sometimes creates problems with not enough power draw to flash the turn signals, but shouldn't do what you report. Two things come to mind. First, are they indeed turn and parking lamps or just turn signals? The original GMC wiring used an 1157 bulb, a low wattage filament for parking lamp, and a brighter filament for turn signal. It had a two wire connector socket, plus a ground strap that completed the circuit. If you have a single element LED wired to the original two wires, it will come on with either the turn signals on or the headlights on (depending on LED polarity, probably just one or the other and not both) as the ground will complete through the other circuit of the miswired bulb. The second thing could be, If it is a two element LED, it may still have a loose ground connection. I can't say why, but turn signals just do strange things when the ground connections aren't good. Just a few thoughts.
Craig Lechowicz
'77 Kingsley, Waterford, MI
|
|
|
|
| Re: Both turn signal indicators on with head/parking lights [message #91684 is a reply to message #91677] |
Mon, 12 July 2010 16:48 |
 |
RF_Burns
Messages: 2277
Registered: June 2008
Location: S. Ontario, Canada
Karma: 3
|
Senior Member |
|
|
I don't have the wiring diagram handy, but I believe the side marker lamps get their "Ground" through the turn-signal lamps. This causes the side lamps to flash alternately with the turn signals. A neat trick made possible because the marker consume much less current than the turn signals..
Your LED lamps however take much less current than the marker lamps so now the tables are turned. I'm thinking your marker lights are now dim, if lit at all.
You will need to separate the marker grounds and ground them directly to ground, but you will lose your alternating turn signal effect. You could wire a relay in the marker light ground, or install a low value (8ohms or so) resistor across the turn signal to up its current consumption and mimic the old incandescent lamps to retain the alternating effect.
Bruce Hislop
ON Canada
77PB, 455 Dick P. rebuilt, DynamicEFI EBL EFI & ESC.
1 ton front end
http://www.gmcmhphotos.com/photos/showphoto.php?photo=29001
My Staff says I never listen to them, or something like that
|
|
|
|
GMCforum
Search
Help
Register
Login
Home
