replacing lighting coil

harleysportster · Post by **harleysportster** » Sat Feb 02, 2008 10:50 am

Brian,
I thought that if your sled has the 4 wire rectifier set-up, the voltage for the lighting is supplied from the battery thru the ignition switch. If I am looking at the correct wiring diagram, power is coming directly from the battery to the B&W wire on the back of the ignition switch. When switiched ON, power is transfered to the red wire which leads to the light switch. Not owning this sled model I can't verify what I am try to explain.

400brian · Post by **400brian** » Sat Feb 02, 2008 4:04 pm

I believe you are correct Pat.

If you have the factory e-start wiring harness for the system, you remove the original plug from the harness ( which is just a couple of looped wires ), and plug in the e-start plug. From that point on, the lighting coil just charges the battery, the lights feed off batt voltage. If you hook a tractor type ammeter in at the circuit breaker, you can tell if the lighting coil is working or not.

Right now for testing purposes, I have put in the original plug, so the battery is back out of the system.

Put the seat and tank cover on the 340S last night, felt good to accomplish something. The old X300 green machine may be making another trip north.

400brian · Post by **400brian** » Mon Feb 04, 2008 4:44 am

Ok, here's what I'm looking at.

My meter is nothing fancy, but it does have a 10 ohm scale.

Checking the resistence at the two yellow wires at the top of the engine connector, I saw little if any resistence. I checked a NOS coil for a '73 500-X8 and saw the same thing.

Fired up the engine, and saw around 20 volts at idle, but no lights when you replace the connector.

I replaced the V. reg with a new one, no change. This wasn't to much of a surprise when I checked for current at the V reg connector and saw none.

After a lot of fooling around, I discovered this: I am getting 20 volts off only one yellow wire. 20 volts ac connected between the two yellow wires. But if I put one lead to ground, I only see 20 volts on one yellow wire, nothing on the other.
I see little to no resistence checking from each yellow wire to ground.

Any thoughts would be appreciated.

JDT · Post by **JDT** » Mon Feb 04, 2008 12:03 pm

Does the tach function?

JDT · Post by **JDT** » Mon Feb 04, 2008 12:28 pm

It is possible Brian that someone changed things from original in the past.
Two more questions...

Does your light toggle switch have two or five tabs on it?

Does the key switch have three or four positions? ex. off-lights-on-start

If rewiring was done everything may function correctly when the e-start connector is plugged into the harness but not when the jumper connector is used.

..............

To answer the question about only having 20 Volts on one yellow wire with the engine connector hooked up; this is normal as the jumper connector ties one yellow to ground.

JDT · Post by **JDT** » Mon Feb 04, 2008 12:50 pm

To be able to recharge the battery the ignition switch has to correctly wired per the diagram as the positive current path goes through the switch.

AND

The negative current path goes through the light switch. The light switch has to be ON to complete the charging curcuit.

If I am reading the diagram correctly this is a strange way of hooking up a recharge system. But as I see it the light switch has two functions. One set of contact switches the headlight/taillight on and the second set completes the charging circuit. If the switch is bad you will see a discharge on your ampmeter.

Likewise if the keyswitch has a bad set of contacts in it the posiitive current path from the rectifier to the battery will be broken; again causing a discharge reading.

And either of these two possiblities(key or toggle switch bad) will also cause the lights not to work.

JDT · Post by **JDT** » Mon Feb 04, 2008 1:02 pm

Did the original lighting coil test bad with your ohm meter? You said it looked brown.
Was is open?

You should test your rectifer with your ohm meter also. If a rectifer fails(shorts out internally) it can cause the lighting coil to burn out. It has to out of curcuit (unpluged) to test .

Rectifers can fail two ways... short out or open.
An open will simply cause it to not supply DC charge voltage.
A short will cause excessive current and burn up the coil.

JDT · Post by **JDT** » Mon Feb 04, 2008 1:21 pm

I looked at the 73 diagram and noted that there is a jumper installed on the key switch that connects the positve side of the charging curcuit regardless of key position.

Anyone know why this was changed on the 74 models?
I never noticed it before.

And I looked at the 72 diagram and noticed a three terminal rectifier. Is that correct??
I've never worked on a 72 before but a three wire rectifier??

HoosierDeereMan · Post by **HoosierDeereMan** » Mon Feb 04, 2008 2:58 pm

Todd,

The '72's are different because the lighting coil has a lesser output. I think 70 watts. In '73 they were bumped up to 120 watt coils. This may account for the difference in the rectifiers.

JDT · Post by **JDT** » Mon Feb 04, 2008 4:05 pm

73 and 74 use a full wave bridge rectifier which has 4 terminls.
A half wave rectifer is simply a single diode thus two terminals.
The 72 has to two diodes with a common tie on the cathode.

This is one case where two halves do not make a whole.

But it is a battery charger not a power supply so it works just fine.

Looking again at the 72 diagram I am positive that is what they used.

........

Brian by verifing if the tach works will clear up some questions.

400brian · Post by **400brian** » Mon Feb 04, 2008 4:51 pm

Before I replaced the coil, tach read half, now it is non functioning. No current registering at tach connector.

The sled / wiring is totally non molested.

Stock on / off light switch. Stock ign switch, off / run / start.

Remember, right now the e-start system is not plugged in.

I see no resistance from either of the two yellow lighting coil wires to ground.
The coil I removed has no resistence between either wire and the frame of the coil. A NOS coil for a '73 X8, shows NO current flow from either wire to ground.
That strikes me as more propper.

The coil I removed, tests exactly like the one I have installed right now, but different from the '73 I have sitting on the bench.

400brian · Post by **400brian** » Mon Feb 04, 2008 5:07 pm

Pat

Would you fire up the sled and see what you read for output voltage from each yellow wire to ground?

Also, what is the ohm reading from each connector to ground?

Thanks

Brian

harleysportster · Post by **harleysportster** » Mon Feb 04, 2008 9:41 pm

Brian,
I can't fire up the sled, it is blocked "in" the garage at the moment. One thing I want to point out is the picture I posted of the ohm readings of the lighting circuit was from my 76 cyclone which has a different style of lighting windings than your sled. The output wattage is the same but the ohm resistance may be different. On the Kioritz /22 engines with CDI, the lighting resistance would be 0.2 ohms
If you are measuring the ohms from each wire to ground, one of the wires will = 0 because it is grounded to the frame if it is plugged in correctly. The other wire will show approx 0.2 ohms or higher.
Measuring the lighting coil on the bench, each wire to ground will show an open circuit.

JDT · Post by **JDT** » Tue Feb 05, 2008 12:26 am

Brian, if you look at the diagram and trace the wires from the tach to the lighting coil you will see that there are only two connectors in that curcuit.

The tach has three wires in it's connector. One is the backlight and the other two go to the Lighting coil.

The connector at the engine is the other connector.

Either one of these two connectors is bad or the associated wire between them is bad.

When the tach only reads half RPM's is not receiving pulses from both lighting coil wires.

When you find the bad connection or wire in the tach curcuit, the lights and battery charging will work.... unless you have multiple problems.

The reason I kept asking about the tach is that it is not dependent on the key switch or the light switch. BUT there is a terminal on the back of the toggle switch where two brown wires with a white stripe are on the same crimp connector and that could be bad.

Just trace the wires and you will see what I mean.

JDT · Post by **JDT** » Tue Feb 05, 2008 12:38 am

While you are at it, put one lead of you ohm meter on any black wire behind the dash and the other lead on the engine case.

This should read zero ohms or very close to it (less than 1.2).
This confirms a good ground connection between the sled frame and stator.

This has nothing to do with the tach but is essential for the voltage regulator.