Tail/Turn Lamp Adapter will not work with LED


Technical information and Q&A applicable to all years and models of Goldwings
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tom84std
Posts: 493
Joined: Fri Jul 13, 2012 7:40 am
Location: Arlington, Texas
Motorcycle: '84 STD 1200
2002 VTX1800
2007 Shadow 750
69 BSA Bitsa
2004 Virago
VW Trike

Tail/Turn Lamp Adapter will not work with LED

Postby tom84std » Wed May 13, 2015 2:12 pm



Building a trailer to use with my bike. When I built one for my Goldwing it was back before LED lamps were available for automotive use. I used 1157 bulbs for Stop/Turn/Tail lamps plus four small marker lights. This was a lot of load placed on my alternator. So much in fact that it would cause system voltage to drop down to 10V indicated on my panel voltmeter.
In building this trailer, I have the advantage of using low current LED's which draw a fraction of the load compared to the old 1157's. This causes me a problem though.
I used a common brake/turn signal adapter with the old trailer to adapt the combined 1157 bulb to the bike's separate brake/turn circuit. It worked fine for years that way. The low power of the LED's however, will cause the semiconductors to malfunction in the adapter. I tried three different adapters before I decided that it wasn't going to work.
I came upon a couple of different ways to do this. Simply adding separate turn signals being one. The fact that my other lamps were already mounted and wired made this unattractive since everything had been located and mounted. Not really any room for adding more lights.
An alternative method of wiring the lights can be done with four Bosch-type relays and four 1N400X diodes available from Radio Shack. Total cost being about the same as the adapter. A little more complicated, but quite doable. This circuit will work with all bikes, or cars for that matter.




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redial
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Location: Kapunda, SouthAustralia
Motorcycle: 1997 GL1500 Spectre Red Aspencade

Re: Tail/Turn Lamp Adapter will not work with LED

Postby redial » Thu May 14, 2015 2:49 am

With the turn indicator, you will find that not enough resistance is there to activate, and one way out of this is to install a standard incandescent lamp on each side. This should provide enough to get the system to work. Otherwise, you need to set up an 'adapter' of some sort to compensate for the low draw of the LEDs.
Len in Kapunda

The world is not going to finish today, as it is already tomorrow in Australia and New Zealand, and other islands of foreign nations such as Guam and Samoa.

User avatar
tom84std
Posts: 493
Joined: Fri Jul 13, 2012 7:40 am
Location: Arlington, Texas
Motorcycle: '84 STD 1200
2002 VTX1800
2007 Shadow 750
69 BSA Bitsa
2004 Virago
VW Trike

Re: Tail/Turn Lamp Adapter will not work with LED

Postby tom84std » Thu May 14, 2015 5:38 am

redial wrote:With the turn indicator, you will find that not enough resistance is there to activate, and one way out of this is to install a standard incandescent lamp on each side. This should provide enough to get the system to work. Otherwise, you need to set up an 'adapter' of some sort to compensate for the low draw of the LEDs.

A good fix for that is to use an electronic turn signal flasher. Several different ones are available from major auto parts suppliers. I installed one on my 84 and it was a pretty easy modification. It's really just an oscillating relay providing a timed pulse and operates independently of whatever the load. Simple hookup (power, ground and output) and it'll last the life of the bike. It's pretty much the same thing as the "Heavy Duty" flashers we had to use whenever we pulled a trailer with a car or truck. Except this one is electronic.


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