12v AC For Headlights?

[MikePA]

In another thread here, I mention restoring my 1984 Wheel Horse garden tractor. One of the items on my 'To Do' list was to get the headlights working. I thought it'd be as easy as running a replacement wire from what was left of one that was damaged up to the headlights. It proving not to be so easy. /forums/images/graemlins/frown.gif

According to the wiring diagram, there's a Diode (Rectifier) near (in?) the engine that has 2 outputs. one of which is labeled A.C. for Lights. This wire goes to a toggle switch on the console. The other wire on the toggle switch goes to the headlights (this is the wire I have to replace). I checked the voltage at the diode and it only reads about 5.5 volts which is not enough to power the headlights.

Does this mean I have to have the engine serviced in some fashion?

Why would the lights run on AC?

 

[Slamfire]

I don't know about yours, but mine only has power in the lighting circuit when the engine is running. There is a small alternator under the flywheel, that is for battery charging and running the lights. /forums/images/graemlins/crazy.gif

 

[chrisjbell]

<font color="blue"> Why would the lights run on AC </font>

I haven't seen it all, and there are some wacky setups out there, but I can't imagine that a small engine is going to use AC for low voltage lights. Did you take the reading with the engine running or not? And was it cranking at high enough RPM to get a generator / dynamo to put out power? Sounds like Slamfire may have your answer...no voltage there until you're generating enough power?

 

[F350Lawman]

I feel for you /forums/images/graemlins/frown.gif

I just totally rewired my Murray and it was apain thta took entirely too long. My friend helped and he is an electrician but we still had probles with all the safeties and other unecessry garbage.

I looked at my schematics and the only AC power was comingoff the stator in the form of a black AC wire that goes to a diode and comes out a white AC wire /forums/images/graemlins/confused.gif

Are you SURE Ac went to the lights? My lights also only work when the tractor is running.

Sorry i can't be much of a help. We ended ripping everything out and wiring it in a logical fashion, minus all the extra junk.

 

[MikePA]

Attached is the wiring diagram for the tractor. The upper left and upper center portion shows the lights circuit. The lights only work when the engine is running and that's when I tested the output from the 'dark green' wire.

 

[slowrev]

I have worked on a couple of older Briggs engines that actually had 2 windings in the flywheel alternator. ! came out as AC for the headlights and the other one was rectified to DC for the battery. Be careful and only use the proper wattage bulbs in the headlights, otherwise you can fry your headlight alternator winding. Also these AC voltage readings may be deceptive when not hooked up to a load ie headlight bulb. And may not be 12 V at all engine speeds. The ones I worked on seemed to vary a lot with engine speed.

 

[MikePA]

<font color="blue"> Also these AC voltage readings may be deceptive when not hooked up to a load ie headlight bulb. And may not be 12 V at all engine speeds. The ones I worked on seemed to vary a lot with engine speed. </font>
Do you think the headlights might work if I just connected everything per the wiring diagram? I checked the B & S website and the regulator for my engine is $70.25! /forums/images/graemlins/shocked.gif

I know the lights work since I connected them directly to the battery to test them and I checked the toggle switch with my digital VOM.

 

[slowrev]

Mike,
I think that would be ok if they are origional or origional replacement types. If the lights are not origional types they might draw too much current and damage the alternator in your engine. The AC should be tapped off before the actual rectifer circuit and should not effect the regulator/DC voltage unless the headlights are drawing too much current ie not origional types. The Briggs manuals I have seen say to ONLY use the proper head lamp bulbs or damage can occur.

 

[MikePA]

slowrev, these headlights are original equipment I got from my Toro/Wheelhorse dealer.

When I read the 5.5 AC volts at the rectifier, the engine was at idle. Assuming I have not misread (entirely possible /forums/images/graemlins/grin.gif) your post, as I increase the rpms the voltage should come up?

Also, would there be a problem with powering these lights from the DC side of the tractor's electrical system?

 

[slowrev]

Yes you are correct the lights will probably be pretty dim at idle and brighter as the rpm's go up. Not sure on the battery powering of the lights. The alternator/regulator might not handle the added current, or might, but at 70.00 or so a regulator I don't think I would want to chance it. I would just hook them up as they were, I have only used mine on any rider or tractor once or twice a year anyway. Just rev it up a bit and they brighten right up.