No lights, Nothing obvious, HELP

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Wallydog

Member
May 14, 2002
37
0
Lights don't work, Nothing obvious, LIGHTS ARE FIXXED!!

Noticed my front light was out a few rides ago and just got around to checking it out. Thought it was just the bulb. Bulbs fine. Further checking shows tail light doesn't work either. I pulled the tank and side covers to see if the obvious loose wire or bad conection existed. All wireing and connections look just great. Looked at my electrical diagram in my shop manuel and it is all Greek to me. Any ideas on an easy fix I didn't think of or how to trouble shoot electrical problems. I have a circuit tester but because there is no fuse in the system I was concerned I might short out and blow a voltage regulater or something poking around with that thing. Bike is a 2001 KDX 220. It does have a brake light wired to the rear tail that used to work also. Thanks much
 
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W

Waffle

Member
Oct 19, 2004
37
0
Unplug the wires to the light switch on the handlebars. Then run a wire (or paperclip) between the two to see if it's a faulty switch.

That would be my guess seeing as how both lights are out.
 
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Wallydog

Member
May 14, 2002
37
0
I tried that sort of. I unplugged the switch completely and direct connected the red and yellow wires to the light together bypassing the switch.. Still no lights. I thought it would be something simple. Would a faulty voltage regulator or CDI have anything to do with no lights? Bike runs excellent so it is not something in the spark plug circuit.
 
C

cr250can

Member
Feb 16, 2005
338
0
not that familiar with that bike. does it have two coils? an ignition coil and a lighting coil? I had a banshee that did that one and it was due to a bad lighting coil.

That is my thought.
 
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Wallydog

Member
May 14, 2002
37
0
How do you test the light coil with out taking the side cover off? Seems to me the bike needs to be running to see if it works. When I direct wired the head light I disconnected the wires with the engine running and I could see a nice spark jump the connection as I disconnected and reconnected that coupler. Is there a main ground in the circuit that you can test? I wonder if I am not completing the circuit with a poor ground somewhere. Can't figure out where the light circuit is grounded to the frame or whatever. I keep thinking of my basic auto mechanics background which has a battery in the circuit not a magneto coil. Thanks for the advice.
 
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cr250can

Member
Feb 16, 2005
338
0
take a voltmeter and test it across the head light terminals while the bike is running it should be like 12-14 volts. If you have that kind of voltage coil is probably good (note: can do the same thing on the rear tail light too.) Does the brake light when you step on the brake?
 
C

canyncarvr

~SPONSOR~
Oct 14, 1999
4,005
0
1. re: '.Should have around12- 13 volts dc'

Nope. It's an AC system. Try to measure output with a DC meter and you'll get squat.

2. re: 'Yes two coils like you stated, the lighting coil being behind the magneto '

And the exciter/sparky coil is also behind the magneto (taken to be 'flywheel'). The light coil is on the top...is varnished copper wire. The exciter is on the bottom..it's potted..covered with epoxy, no copper visible.


3. re: 'How do you test the light coil with out taking the side cover off?'

Disconnect it from the light switch. Check for AC presence when the engine is running. Keep in mind that the VR is not in the circuit at that time. Voltages can approach 100VAC.

4. re: 'Is there a main ground in the circuit that you can test?'

The lighting coil is grounded at the coil. One end of the coil is gnd, the other (yellow) goes to the switch. Ground in the system is frame ground. Keep in mind that testing a circuit with one meter probe to ground...seeing a proper signal/voltage...but things still dont' work is a sign that the ground the harness is trying to use is likely the problem. You are introducing a 'good ground' with your meter. Better to check a circuit with your meter ground connected to the harness (where it should be). That way you are using what the bike is trying to use.

5. re: 'Can't figure out where the light circuit is grounded to the frame or whatever.'

As stated...the lighting coil is grounded at one coil end..under the flywheel. The VR (that's 'Voltage Regulator' btw) isn't grounded there. Take your tank off and you will see a number of grounds in the ignition coil area. IF the problem was a missing VR ground, you would have blowed up everything (light-wise) by now.

You mention having a 'circuit tester'. I assume this is a DC tester? It's of no use to you on an AC system.

Get a VOM (Volt-Ohm-Meter). Doesn't need to be a $100 meter...any little meter from RadioShack will do. Start looking for AC at different points in the system with the bike running. The yellow wire to the switch is unregulated (like I already said) and can get pretty hot..around 100VAC (volts-AC). As soon as the switch is 'on', the VR is put into the circuit (the red wire). You should see the AC drop to around 12VAC. If you see that drop, you know the VR is working.

If you don't have a meter, how do you know your bulbs are good? By looking at them? That is not too good a way of sorting that out. Check them with your new meter...set to ohms. Keep in mind that there are TWO filaments in the headlight, but only one of them is used. If you 'see' or 'test' a filament as good..make sure it's the one the bike is using (look at the socket to figure out which one that is).

Most likely thing wrong is you have two burned out blubs. That's most likely 'cuz that's most common.

Your new meter will sort that out quickly.

BTW..DO NOT do anything that will take the VR (red wire) out of the circuit. Example: Bypass the switch by jumpering the yellow wire to the headlight while you give it a 'good' ground with another jumper to the frame.

Touch the throttle and your blub just got ate by 100VAC.
 
W

Wallydog

Member
May 14, 2002
37
0
Thanks CC. I just spent a little time on my lighting problem after your suggestions. Wanted to check for lighting coil output to avoid taking the magneto cover off. I connected my VOM meter up to jump the yellow wire going to my switch and got a strong needle reading of 40 VAC at idle. Turned the switch on and went to the red wire side and got the same reading. ????? So WTH. I tested continuity in my bulbs and the front is fine. Rear is an LED 1157 and doesn't show continuity that seemed weird but I can get another one. I put my tester into the sockets to test for juice at the sockets and neither one show on the VOM. One probe touching the grounded shell and the other probe touching the "hot" solder bump. No juice there unless I am doing something wrong to test the sockets for power.
It appears that the lighting coil works. My thought is that the VR has shorted making the lighting circuit incomplete so no lights. Just a guess from someone who barely has a clue.
I didn't have the time to pull the tank and look at the grounds around the coil. Any more ideas would be greatly appreciated. Thanks.
 
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Wallydog

Member
May 14, 2002
37
0
I am totally baffled. Pulled the seat off to check all grounds and all wires. VOM continuity tested every single line. All have continuity. No shorts. VR shows a reduced continuity as expected due to internal resistance. Light Coil shows continuity also. Sooo..... any ideas?
 

ellandoh

dismount art student
~SPONSOR~
Mi. Trail Riders
Aug 29, 2004
2,958
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test the socket again only by putting red lead on hot side then put black side poked into some moist ground (as in soil in your yard) or touch black lead to something metal in garage you know is grounded then youll know if light socket is not reading because of the hot or neutral side


from there you keep testing closer and closer to the socket narrowing it down whether this is the hot or neutral

i dont own a cycle with lights but if these wires are anything like the 18awg i use to install occupancy sensors then 1 pinched wire can stop the flow of juice . when narrowed down you think it couldnt be there so you look elsewhere.......mistake, it will be there. just narrow and narrow youll find it
 
K

KdxChode

Member
Jun 18, 2001
327
0
If you have 40 volts then it is just blowing the bulbs out.

The LED in the rear won't show continuity because it is a light emitting diode not a bulb. Diodes only let current flow in one direction. It is probably blow out though with that high of voltage.

Also, you will get a voltage reading on both wires because it is AC power. This is also why your LED tail light flashes at low rpm and gets steadier as the rpm's build.
 
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Wallydog

Member
May 14, 2002
37
0
So a 40 volt reading on both sides of the on off switch indicates the VR is not doing its thing? Front bulbs show continuity so isn't blown, thanks for explaining LED bulbs. I just do not get power to show in any of the sockets.
 

ellandoh

dismount art student
~SPONSOR~
Mi. Trail Riders
Aug 29, 2004
2,958
0
 
W

Wallydog

Member
May 14, 2002
37
0
Fixxed my lights!!!

Thanks all for the responses. Bottom line is a VOM meter is crucial to troubleshooting electrical problems. Continuity testing and AC voltage output checking all through the system finally got me on track, isolating areas as you go. Finally found a short in the hydraulic brake switch. One of the wires was grounded on the frame. I learned allot about how the "juice" flows on a KDX. Thanks again. I think one of the best things about motorcyycles besides riding them is having succesful mechanical work done by yourself.
 
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