640 lighting

[Rick Jones]

Hey All,

I"ve inheritied a Ford 640 that has been converted to 12 volts and I want to wire up the lights. I"m kind of confused on why when I pulled the bulbs out of the three housings (two front, one rear) each one had a lead going to ground. I would have thought one lead would be positive the other negitive and the ground would be a frame type ground back at the battery. Are those grounded leads left over from the 6 volt system? I don"t know if the lights have ever worked since it"s conversion. Anyway, does anybody know of a simple 12 volt wiring diagram out there I can use or know of a website that would have one?

Thanks

Rick

 

[AOK]

I would think if you have 2 wires at each socket, one would be the positive coming from the switch and the other is the negative, attached to the frame/sheetmetal. They just use the frame or sheet metal as the negative, no need to run the second wire back to the battery since that negative goes to the frame/sheet metal. Make sense?

 

[souNdguy]

Lotsa times 50yr old sheet metal don't make a good ground, and people run 2 wires to each lamp.. hot, and ground.

'Hot' will depend on your polarity.

if 12v negative ground.. then 'hot' is positive.. etc.

incandescent lamps don't care which terminal gets +/-...

soundguy

 

[Old Ford Mechanic]

Rick,the other guys have given you correct advise.What you can do is use one wire from each light for a common ground to the tractor chassis.Use the other wire from each light as the power wire to the light switch.Your light switch should be two position with a fuse.You can connect the two headlights together and use one wire to the switch.And another from the rearlight.

 

[Jim.UT]

That ground wire inside the headlight housing worked good when the tractor was new. Fifty or more years later it's not such a hot idea. I ran ground wires alongside my hot wires back through the hollow mounting bolt and then grounded them to one of the screws that holds the front emblem on. I sanded off the paint at that spot first to get a good ground.

Either 6V or 12V sealed beam lamps are available to fit those housings. You probably still have 6V lamps in there. Just go to the store and buy 12V equivalent lamps and you're set (once you get the wires sorted out).

The 12V number for that lamp is 4419. The 6V lamps are either 4019 or 4013. Your lamps may have the number and the voltage stamped on the back side (wipe the dust off to see it).

 

[Rick Jones]

Thanks for your reply Jim. I checked the bulbs before I mounted them and they all worked with a jumper wire to the 12 volt battery so I'm good there. None of them were in mounted on the tractor though, they came in the box of parts I also inherited. So then when you wired your lights did you just more less run a series circut with, let's say a red wire going to one side of the light bulb and then a black wire running from the other side? You grounded on the emblem nut. Where did you run the hot side to? I'm thinking either the + side of the battery or the plus side of the starter relay.

Thanks again.

Rick

 

[Jim.UT]

The hot lead runs to the light switch. I used a generic push-pull headlight switch from AutoZone (about $5). It has a fuse built into it.

You can run the power directly from the hot side of the terminal block or you can run it from the ignition switch. I chose to run it from the terminal block. That means I have to remember to turn the lights off after shutting the tractor down, but the stories I've heard about the inherent weakness of the key switch made me not want to run any unneccesary additional voltage through it.

 

[Mashbox]

I think what Jim is saying is to run the ground conductor from each light through the hollow mounting bolt, connecting them both to a ground source, such as he did using the emblem mounting screw.

Then take the hot wire from each light, passing through the hollow bolt to underneath the hood, connect these two wires together along with a third wire which will run to the load side of the fused two-position light switch. The power connection for the switch will come from the solenoid, which connects to the ammeter, which connects to the alternator.

Someone please correct me if I am wrong.