Outdoor Power Equipment and Small Engines - Charging System Question

Hey guys, I was hoping someone could help me out. I just put a 6hp OHV Tecumseh Power Sport motor in my minibike. I got the motor with the built in alternator, so I could run a headlight. The motor has a red wire and a yellow wire coming from the alternator. I have verified the red wire outputs voltage, which seems to increase over 20 volts at high rpms.

I just wanted to run the alternator to the light, so I could use it when the bike is running, but obviously the voltage is too high. Can someone shed some light on what I need to do to wire up a headlight? Also what does the yellow wire from the alternator do?

Thanks in advance.


SAL

Somewhere in here there is a tecumseh expert, you may want to see if he replies. If it were me i would first determine if it is AC or DC voltage, you will probably need to know your amperage also.IF you have low amperage your voltage will drop with a load,it mite be that the light would be fine.

Sal,

If the alternator has a red wire & yellow wire, it's a 3-5 split
system alternator. The red wire contains a diode that converts
A/C current from the alternator to D/C for charging the battery.
The yellow wire side is 5 amps of A/C current, and you can run
a headlamp directly from that side of the alternator harness.

Tcumcman

Tcumcman, thanks for the reply.

So I use the yellow wire as the power for the headlight? And I assume the other side of the light goes to ground? Does this mean I don't need to run a battery, and do I leave the red wire from the alt disconnected?

Thanks again.

Hello Sal!

I would suggest using a battery...just a small 12 volt one...for this system. The reason I suggest this is because running from the yellow wire, you will have lights that brighten and dim according to engine rpm. The battery is a capacitor that will compensate for the differences in voltage that are produced by the charging stator. I would run the red wire to the positive post on the battery, and connect your lights from the batt. itself. Make sure the diode is in place.

Hope this helps!

Sal,

Cheese gives good advice !! I suggested the A/C side of the
alternator because I didn't know what "type" of sealed beam
or headlamp you intended to use. As Cheese says, the changes
in RPM's will cause the output of the alternator to fluctuate. It
makes the headlamp brighten and dim as this occurs. The red
wire side is 3 amps of D/C current, and you can run this wire
DIRECTLY to the "+" side of the battery as Cheese said. This
keeps the battery charged. If you operate the headlight off
the battery current, it will remain constant at one brightness.
This is probably the way it should go. I am kinda "surprised"
that this engine has a "split system" on it. Most of them just
have a 3 to 7 amp D/C system and the lighting comes off the
battery current anyway.

Tcumcman

Thanks guys, that's good info :) .

Just to make sure I understand right, this is what I've gotten out of your replies...

If I run just the headlight with no battery, I need to run the yellow wire to the + side if the light, and the - side of the light to ground. No need to connect the red alt wire to anything. This will operate the light, but make it fluctuate with rpms.

If I run a small battery, I need to wire the red wire from the alt with the diode to the + side of the battery, run the negative side of the battery to ground, then run the power for the headlight off the battery, and no need to use the yellow alt wire for anything.

Am I understanding this all right?

Thanks again. :cool:

BTW Tcumcman, this is the engine I got: http://www.smallenginewarehouse.com/product.asp?Product=993

I'd say....YOU'VE GOT IT !!
Let us know if we can help further and let us know how it does
for you.

Tcumcman

Sal...the only thing missing is a switch. If you use a battery, then you will need a switch to turn the light on and off, or it will stay on continuously until the battery dies (when you shut down the engine). You don't need a switch if you just run from the yellow wire with no battery. I'm guessing you knew that, but since it wasn't in your wiring plan above, I thought I'd mention it to be sure. Just a simple toggle switch will do.