tail light wiring

Tiger Joe · Jul 22, 2015

trying to install a factory tail light on my 640 and my 871.

Both of them have the same issue:

The factory wiring is in place to the rear fender. however I am getting a voltage drop thru the wire.

ex: 871 is still 6 volt system. head lights work fine. all original wiring in place, check voltage at tail light- I have around 3-4v.

640- converted to 12 volts. original wiring all there, head lights work fine with 12v bulbs. check power at tail light- 3 volts.

I cannot follow the wire as it goes into the main harness, but I checked for continuity so know its good, tired hooking directly to battery and still nada.

Is there some kind of resistor in the tail light wiring? or is this just old wiring?

old · Jul 22, 2015

Sounds like old wires that have cracked insulation so have some sort of short to ground which if used may cause a melt down of the wiring harness

souNdguy · Jul 22, 2015

continuity?

so you are using a meter that has probably a megaohm or ten, or a gigaohm+ of input impeadance.. and because it can pass micro amps of signal thru the wire, you think it is good to handle a 3-6a load?

if you have volts on one end and less on the other.. you have a problem!

could be bad connectors, nearly coroded thru wires, bad connection at the switch or in the switch, and depending on exactly HOW you measured it, maybee even insuficient ground thru 60 year old painted and rusty sheet metal.

rvirgil_KS · Jul 22, 2015

I have an 8N that I had problems with tail lights on the fenders. Power was good back to the lights.

I found the problem to be rust, corrosion, sand and dirt where the fenders mounted to the axles was not giving a good ground. Took several tries but finally got it clean enough to make a good ground and lights worked. Also don't overlook corrosion between bolts holding fender skins to the supporting fender framework.

Try checking your rear light voltage with meter ground connected at the transmission case. Increased voltage reading will confirm bad ground between that point and the light bracket on the fender.

You can also confirm problem by running a wire from light case to a good ground point on the main frame.
As mentioned, if wiring has brittle, cracked insulation or bare spots a rewire job is needed

Tiger Joe · Jul 22, 2015

I am grounding my meter directly to the battery when I am checking voltage.

I can certainly believe the wiring needs replaced, however I just found it odd that two totally separate machines had the same issue.

tail light wiring

Tiger Joe

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old

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souNdguy

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rvirgil_KS

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Tiger Joe

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