Shipper Posted June 2, 2010 Share #1 Posted June 2, 2010 I'm trying to add an LED strip to my brake light. When my brake light is on (brakes on) I'm pulling 11.5 volts, but when its not on I'm still pulling 7.5 volts. This low voltage causes my LED to light defeating its use as an additional brake light. Is this voltage normal? My existing brake and running light works fine, but this low voltage is messing me up. Thanks for any help! Link to comment Share on other sites More sharing options...
Dave77459 Posted June 2, 2010 Share #2 Posted June 2, 2010 It seems to me that you are tapping the wrong wire. If I recall correctly from installing the run/brake conversion kit, there was a wire for running and another for brakes. If you get the right wire, there will be current only when the brakes are applied. Here are the installation instructions (PDF) for the kit I bought. It shows that you should tap the blue wire for brake lights. Hope this helps, Dave Link to comment Share on other sites More sharing options...
GeorgeS Posted June 2, 2010 Share #3 Posted June 2, 2010 If you have " Low voltage " its not a light bulb problem. If your battery is fully charged, and there is " NO " bad wireing, the voltage should never go below 11.8 with All lights " ON " and engine " OFF ". ( IF battery is fully charged ) With Engine running, the voltage should never go below about 12.5 With EVERYTHING ON !! . If you are getting a substantial drop in voltage after hooking up this " light Strip ' as you say, then there is something wrong with it. Recheck all the new wires you are useing. Check your Charging voltage at the Battery Terminal, with engine running, it should be at least 13.2 volts or higher, Use a test voltmeter, not the gauge. With engine " OFF " your Lead Acid battery if fully charged, should read 12.2 to 12.3 volts. IF NOT, Check the fluid level in the battery, and Re-Charge it !! ( Use a charger, not a trickle charger ) Charge at 2 Amp rate or higher for at least 5 hours. Link to comment Share on other sites More sharing options...
Venturous Randy Posted June 2, 2010 Share #4 Posted June 2, 2010 George, it isn't a low voltage problem as much as having voltge when the brakes are off. I suspect he has a ground problem on the light wire and it is feeding back thru the brake wire. RandyA Link to comment Share on other sites More sharing options...
Guest tx2sturgis Posted June 2, 2010 Share #5 Posted June 2, 2010 Shipper, you have it connected incorrectly...and most likely you have the wrong ground wire. Try running the black wire from the LED to a solid ground on the frame or the luggage rack and then take your readings again. Link to comment Share on other sites More sharing options...
KiteSquid Posted June 2, 2010 Share #6 Posted June 2, 2010 Shipper, you have it connected incorrectly...and most likely you have the wrong ground wire. Try running the black wire from the LED to a solid ground on the frame or the luggage rack and then take your readings again. I would run the ground to where the battery ground cable connects to the frame, in an effort to NOT introduce ground loops.... Link to comment Share on other sites More sharing options...
Guest tx2sturgis Posted June 2, 2010 Share #7 Posted June 2, 2010 (edited) I would run the ground to where the battery ground cable connects to the frame, in an effort to NOT introduce ground loops.... I should have said for testing, run the black wire to the frame or the luggage rack...after confirmation that it all works well, then hooking it to the battery would work fine. Ground loops arent normally a problem except in audio, AC, and RF work, and neither applies here. Edited June 2, 2010 by tx2sturgis Link to comment Share on other sites More sharing options...
Shipper Posted June 2, 2010 Author Share #8 Posted June 2, 2010 Never install two separate things at the same time. I had just installed an LED brake light bulb in place of my standard 1157. Worked fine. Running lights OK, Brake lights OK. Then I tried to wire an LED pulsating strip that was supposed to work only when the brakes were applied. It worked with both the running lights and was slightly brighter with the brakes. Not good to have pulsating running lights (not even sure it's legal to have a pulsating brake light). To make a long story short, the LED bulb used a resister to reduce the voltage to 7.5v for the tail light and 12v for the brake. The strip would operate on the 7.5v so it was on all the time. The 1157 bulb is a dual intensity; so put the 1157 back and problem solved. Thanks for all the replies! Link to comment Share on other sites More sharing options...
CMIKE Posted June 3, 2010 Share #9 Posted June 3, 2010 Could be leaking through the LED's giving you that voltage while it is off. I got a set like that once. I had to install a diode to block the running light voltage from interfering with my brake like functions... It was about 7.5 volts just enough to make my Knight rider sequential LED to think the brake was one. Link to comment Share on other sites More sharing options...
Shipper Posted June 3, 2010 Author Share #10 Posted June 3, 2010 Could be leaking through the LED's giving you that voltage while it is off. I got a set like that once. I had to install a diode to block the running light voltage from interfering with my brake like functions... It was about 7.5 volts just enough to make my Knight rider sequential LED to think the brake was one. Ditto! Mine is a Knightrider too and I decided not to get a diode for a $6 bulb. When I get back from my Skyline Dr ride, I'm going to look at their LED boards which have a diode. Thanks again to all! Link to comment Share on other sites More sharing options...
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