Newbie w/ tc125 elect problem

[ANCIENT TC125]

ok

The box with two arrows is the VR. The two arrows are double zener diodes or clipping diodes. It would be easier to see just the lighting circuit to distinguish what is going one here.

Tnx

Steve

[jabcb]

Take a look at the portion of the wiring diagram I've attached.

See the wire connecting the lighting switch & dimmer switch that is labeled Gr & is shown as gray. (at bottom of pic)
That is the wire I mentioned that carries AC to the lights.

Now look at the arrow I've added.
That is a multiple-wire connector for the Gr wire -- it likely is in the headlight bucket.

Add another wire to this area & connect that wire to the AC regulator.
Also mount the AC regulator so that it is grounded.

A NOS regulator is a waste of money. A modern AC regulator will work better & is a lot cheaper.
You might even find one cheaper than the one from Rex Caunt.

[ANCIENT TC125]

JABCB

You are right. If you look at the 77 wire chart, that is exactly where they connected the VR.

Have to see how it goes when I get the bike back together. Going to separate out just the lighting circuit so I can see where my problem with the high voltage is coming on my present model without a VR. Then if I can't find the solution, I think I'll opt for plan B and go with the battery circuit and Halogen or LED light.

Sure appreciate the help

Steve

[jabcb]

Your bike already has two separate electrical circuits.

The alternator charging coil goes to the rectifier & provides power to the DC circuit. Voltage on the DC circuit is regulated by the battery.

The alternator lighting coil provides power to the AC circuit for the lights. Voltage is not regulated.
The engineers selected an alternator output so that the lights were marginally bright at low rpm & didn't burn out too quickly at high rpm.

Upgrading to a car battery wouldn't solve your problem of the headlight burning out.

Also, you should use a conventional battery that requires periodic addition of water. Modern maintenance free batteries are designed for use in electrical systems with well-controlled voltage.

[ANCIENT TC125]

1974 WIRE CHART ATTACHED

Actually the 1974 TC 125 has four coils. The circuit chart for this bike's headlights is annotated. Note no resistor or regulator included.

When I get this bike back together I will measure voltages from these four coils and whether dc or ac.

Thanks for the Help. Still evaluating which way to go. Regulator and new headlight in the mail.
http://www.amazon.com/gp/product/B00GNU ... ailpages00" onclick="window.open(this.href);return false;


tnx

Steve

[ANCIENT TC125]

Here's a photo bucket copy because the list won't let me upload

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[ANCIENT TC125]

http://s375.photobucket.com/user/homecr ... b.png.html" onclick="window.open(this.href);return false;

[ANCIENT TC125]

OK! I received the Rex Caunt voltage regulator today and installed.

Voltmeter reading on lighting circuit with VR installed:
idle: 8 volts ac
Reved 11+ volts

(Manual says =6volts idle and top end 9 volts)

With VR disconnected
idle: 13.5 volts ac

reved : 30+

Do you think the previous owner installed a 12 volt lighting circuit coil?

Don't want to install my new headlight. Don't want to blow it up. Will try a 12 volt VaNAgon to see if a 12 volt headlight will work.

If I can't find a resolution here, I'm going to go to plan B and wire off the battery circuit.

Any inspiration would be greatly appreciated

Steve
Centerlessville, Utah

[jabcb]

Alternator voltage decreases as you increase the load.
With no load, you got 13.5 & 30 VAC @ idle & revved.
With the VR as the only load, you got 8 & 11 VAC @ idle & revved.
With the headlight + VR you will get even lower voltages.

I don't know how the VR is designed.
It likely has a limit to how much it can control voltage.
The voltage likely will be fine with a 6V headlight + the Rex Caunt VR.

You can confirm this by adding another load.
A turn signal bulb would be a good & cheap test load.

[ANCIENT TC125]

I put a headlight I had out of a 79 VW Dasher (H5006) on the headlight circuit. I t lit up and didn't blow when I revved the engine. Volt meter showed 6 to 7.5 volts as I increase engine speed. Interesting it showed the same voltage on both hi and low terminals of the sealed beam even though I just had it switched to hi beam. Must have been drawing current thru the VOM.


Think this is the way I am going to go. The new 6 volt H4 light I purchased is deeper and would require me to modify the headlight bucket. (http://www.amazon.com/gp/product/B00GNU ... CAHSVQHA4B" onclick="window.open(this.href);return false;)

The H5006 are readily available and seems to work well enough to get this bike safety inspected. Which is all I really need a headlight for.

Thanks again for all your help

Steve
Centerlessville, Utah

[jabcb]

I was expecting results like what you got.
The Rex Caunt VR is controlling the voltage but it just didn't have the current capacity needed when you didn't have a headlight.

The H5006 is a 12V 35/35W headlight.
At 6V its only going to be about 9/9W, which is really dim.
Don't know what your state laws are -- the H5006 might not pass inspection because its too dim at 6V.

There are 6V headlights that have the same shape/dimensions as the H5006.
A stock Suzuki headlight might be another option -- not sure about the one you need, but the ones I get occasionally show up on eBay for reasonable $$.

[ANCIENT TC125]

Light just has to illuminate to get pass "safety" here.

I have a 6 volt, 35 watt seal beam

http://www.amazon.com/LIGHTING-Motorcyc ... PNGX3Q095Y" onclick="window.open(this.href);return false;

but it is 3/4" deeper than the OEM, and with all the extraneous wiring in the headlight bucket, it won't fit without extending the bucket. I should have bought the 4020, but I liked the idea of a removable h-4 bulb. Do you know of any cheap, deeper, 5.75" headlight buckets that might fit?

TNX

Steve

[jabcb]

There are a lot of aftermarket headlight assemblies listed on eBay, but I've never used any of them.
Someone else might have some suggestions.