Cub with Voltage to lights but they won't work!!!!!!

I have a 1965 IH Cub with 6v at the headlights. When I attach the wires to the lights, they won"t work and the voltage drops to the millivolt range. Lights are good (function with a 6v lantern battery attached). With both lights detached from supply wires, they read 6.4 volts. When I attach one light, the power drops across the entire system. Lights stopped working last summer. Have installed a new battery.
What would cause this voltage drop?

Any help would be appreciated.

Remember when you hook up the lights that you may have positive ground.

Did you try reversing the wires?

Most lights are grounded to the frame so if you hook them up backwards they will not work.

The reason it will work with the lantern battery is, that battery is not grounded to the frame of your tractor.

I may be all wet if you have already tried to switch the wires around and the problem still exists.

Gary

I believe your issue is with the supply. A poor connection at any point in the supply wires will allow a typical meter to read almost full battery volts when no load is on the circuit. But! If the circuit is loaded (light bulb is installed) the high resistance (corroded) link will just stop flowing electrons. (for the same reason a poor battery connection in a car will allow the idiot lights to come on with the key, but go out when the starter is turned on as a load)
Proceed this way:

Put one light into the circuit (as you have been).
Use a hot wire (from the battery Negative (assumes 6v pos ground)) long enough to get to the light. (be careful with it because it can make sparks and smoke if touched to ground)
Touch the terminal on the light that is attached to the normal supply wire (I bet the light now lights up.)
Next follow that wire back to the light switch and touch the hot wire to the terminal on the switch that is connected to the light. (again I bet the light lights up)
Now touch it to the terminal going into the switch from the fuse (now I will hedge by saying this if no lights, the switch has high resistance.
If lights, Move the hot wire to the input to the fuse. (again if no lights it is high resistance in the fuse, or holder). If lights, go to the terminal on the amp gauge supplying the fuse.
Then to the other side of the amp gauge. Then to the connection at the starter switch.

In each case you are replacing the source with a (fresh) hot wire electron path. One of these will make no difference (light will stay off) that thing needs cleaned and shined up, sprayed with corrosion inhibitor, and sealed against further corrosion. Best of luck, JimN

It makes no differance which way the current flows through the bulb. They will burn either way. Check for bad grounds also.

Your right it will flow either way, but if the blub holder is grounded to the tractor and you put the neg on the ground wire and and it is a positive ground tractor it can short out.


Gary

I agree with Jimbos good assessment. Regardless if theres an extermely high poor/resistive/corroded connection somewhere in the voltage supply circuit (from hot ungrounded battery post) a good voltmeter (an "ideal" one has infinite resistance) will read near full battery voltage out on the end of the supply WHEN THERES NO LOAD ATTACHED.

HOWEVER if you place a load such as lights on that bad supply circuit then theres a current path to ground and current throught that high resistive poor corroded connection causes an IR voltage drop so the lights arent left with much.......However if theres a high resistance short or load the current should be limited (E/R) and the batteries voltage shouldnt drop much... Its when you have a low resistance high current draw the batetry voltage can drop as its NOT an ideal unlimited energy supply.

John T

You have gotten the best advice possible in the above offerings and I will only add or reiterate that the ground must be really good. Had a problem similiar with an A and had to ground just about everythng in the lamp to get it to work, now no problems. Henry

Guys,

Thanks for the detailed advice, really appreciate it. I'll take the hood back off and start chasing the spark with the jumper wire from the battery.

Paul

do you have the lights on bright (switch all the way to the right)? If you have a light switch with the fuse on the back clean the clips that hold the fuse, they frequently get dirty and do not make good contact.