Re: (ET) Disappointing 36vdc LED headlight results

I had a similar problem for a long time except mine would not work during use and then would flash when I turned then off - I don't use the original wiring. I use constant current supplies feeding individual LED's.

There were two problems in play. First, The power supply I was using was tapped, which essentially cut the voltage available to only 24V. This would cause them to not work when the voltage would sag almost any. I rewired only to find they still behaved strangely or didn't work at all. It turned out that the original fuse block, which I use for my lights, control, and field fuses, had a bad terminal. If you pushed it to the side it worked, but if you left it alone, it would easily vibrate to where it would not make electrical contact.

So, lesson learned, check the fuse block. If the terminal does not make contact, it will act like an open circuit, but when a voltage spike occurs (as can happen when you turn it off and the field collapses), it can be enough to make the current jump the tiny gap and make the lights flash.

David Brandt

From: Charlie <medievalist gmail com>
To: Elec-Trak <elec-trak cosmos phy tufts edu>
Sent: Monday, February 18, 2013 11:52 AM
Subject: (ET) Disappointing 36vdc LED headlight results

A couple months ago I bought socket-compatible 36v LED lamps for the
headlights and dash light of the I5. They were expensive and took a
long time to ship.

I thought I'd just be moving one wire - I forgot that the I5 has a
12vdc horn which is jumped into that circuit (Geo's site has pictures
of the AP69 horn and wiring).

But anyway I hooked them up last week. They fit perfectly, correct
bases and polarities. The dash light glows weakly at 12v or 18v but
works well enough for the purpose at 36VDC - I consider that one a
success.

The headlights do not come on at all at 12v or 18v, glow weakly at
24v, and behave kind of strangely at 36vdc. When you flip the switch,
the LEDs flash very brightly, brighter than the old 12v incandescents.
But that lasts only a fraction of a second, then they settle down
into a useless, weak glow no more illuminating than a single firefly.
You can do this repeatedly and they flash/glow every time.

Very disappointing. I am considering unsoldering the unit, to see if
it has semiconductors under the LEDS.

--Charlie

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