Possible to use AC only

14 replies to this topic
  • cmayer31

Posted March 20, 2010 - 03:58 PM


I'm putting together a lighting system on a 1999 WR400F. The bike is titled as street legal in CA, but the previous owner never put an electrical system in.

Is it possible to set up turn signals, horn, and brake light using the AC system currently on the bike?

I know most people install a regulator/rectifier to go DC and wire in a battery. If at all possible I'd like to avoid going that route.

I also suck at wiring so the simpler the better. :thumbsup:


Posted March 21, 2010 - 08:51 PM


I don't see why not, you just won't have anything that works w/o the engine running. Technically, not legal that way in California, but if it's already registered, what the heck. I would still use a regulator/rectifier rather than the stock ac regulator, just so if you want to add a small battery later it will be an easy add on.

  • jsantapau

Posted March 22, 2010 - 06:58 AM


the horn won't like a/c

  • mrlopez

Posted March 22, 2010 - 07:10 AM


Well I just finish my 2000 wr400 conversion on the electrical and I'll say you would need to use DC it was a pain but I got it all done the ac on the bike it's probably not enough watts(99 only has 85 watts 2000 has 100watts) if you going to use on the street it would be to dim on idle and I think your asking to get pull over when they can't see your lights turn signals etc so if you have ??? Let mw know I'm also in California

  • FasYankee

Posted March 22, 2010 - 10:31 AM


man, wiring that thing is so easy, get the lowdown at www.farplaces.com that guy was even kind enough to include schematics. Get the 7 wire conductor from a trailer place, get the battery from interstate and stuff it in the airbox, also put kill switches (lights and ignition) inside the subframe grab holes.

Should take you a day to get it wired if you have no experience, an afternoon if you know your way around a schematic. I would go with the non-relay'd version (there's 3 on the website) I tried the relay'd one, had too many diode issues, so went to the switched one, and now just remember to shut it down properly when I get off.

G/L man!

  • cmayer31

Posted March 22, 2010 - 06:55 PM


Thanks for the ideas! The bike is my roommates and I don't know how much he plans to ride it on the street. Right now I'm just trying to make it "look" completely street legal for the short trips down the road.

farplaces site is great and I guess I'll spend next weekend trying to get the parts and put it together.

  • pablo83

Posted March 22, 2010 - 08:21 PM


the horn won't like a/c

You can get AC horns. Vespa had an all-AC system a while back. Do an eBay search for Vespa Flower Horn (the grill was kind of flower-looking; very manly).

I think the biggest problem is finding an AC blicker controller. I've never seen one of those.

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  • Birdy426

Posted March 22, 2010 - 08:42 PM


Vespa also had an AC flasher for the turn signals, but they are pricey. By the time you buy one, you cold pay for the regulator/rectumfinder

  • umu24013

Posted March 23, 2010 - 07:10 AM


A standard thermal flasher will work on ac.

  • schrode

Posted March 23, 2010 - 07:18 AM


it seems like a hassle to me. a basic dc setup is pretty easy.

why re-invent the wheel? particularly if you're not electrically inclined. seems like a headache waiting to happen. my .02


Posted March 23, 2010 - 08:11 AM


it seems like a hassle to me. a basic dc setup is pretty easy.

why re-invent the wheel? particularly if you're not electrically inclined. seems like a headache waiting to happen. my .02

Agree, dc is really easy. You only need to swap in a reg/rec instead of your stock ac regulator and add a small battery downstream of that. The battery will fill in the gaps in the electrical power for when the bike is at idle. If you are using a fairly low power stator, then keep your headlight at 35 watts rather than 55.

  • jsantapau

Posted March 23, 2010 - 08:11 AM


My electrical theory has a lot to be desired but I believe that when you convert ac to dc you will lose 1/2 of your power. It is my understanding that when you rectify the power you are basicly just cutting off the bottom of the sine wave(?) so not only do you cut off 1/2 the power but now there are gaps in the flow of power (headlight flickering like a strobe light at idle). If someone could get away with what they need in a/c atleast they won't lose energy trying to convert it to something other than how it was originally made.

If a battery and a taillight that has to be lit for a certain amount of time is recquired by law how would the thought of only converting enough electricity to keep a small battery charged to run a L.E.D. light for the tailight only work out.

can anyone prove or disprove my thinking with some explanation as to why?

  • pablo83

Posted March 23, 2010 - 05:44 PM


can anyone prove or disprove my thinking with some explanation as to why?

I'm no elec engineer either, but according to this website (clicky) I think you're right. If you look at the rectified wave forms (on the volt meters on the right of each diagram) I think it shows what you are talking about.

  • Birdy426

Posted March 24, 2010 - 08:52 PM


A standard thermal flasher will work on ac.

Agreed, but there isn't enough current to create a "delta T" in the flasher with AC...

  • umu24013

Posted March 25, 2010 - 01:28 PM


I've used a cheap thermal flasher on a wr400 the whole last year on AC and on DC with filament type bulbs.
Now I'm going to install a high quality electronic flasher because it can run LEDs and is immune to vibration and current drops at idle RPMs.


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