MTFCA Forum

I can't get my head lights to work on my 1927 coupe. I have installed new wiring and have checked and rechecked it against the Model T Wiring Diagram. I have installed the new parts per the diagram on page 166 of Lang's 2021 catalog. I have had the switch restored.

I would appreciate any thoughts on what may be the problem.

Check the continuity of the buckets to the battery"ground and also to the socket protruding out the rear of the bucket.

Here are photos of the restored switch.

Frank, Could you walk me thru how to do this?

I didn't mention it, but the tail light doesn't work either.

The negative post of your battery is grounded to the chassis and all electrical components derive their ground from the chassis. If you painted everything before assembly, it is possible that the paint is keeping the headlights and other electrical components from grounding. You may need to rig up a ground wire from the headlight to a bare area of the chassis to see if that is the problem. One way to invisibly ensure a good ground is to remove the bolts holding the component and with a rattail file, file off the paint inside each hole making a pathway to the chassis through the bolt. This would include the fender holes. The bare bolts inserted through the holes will connect all the parts so as to retrieve the negative charge from the chassis, directing it to the various electrical components. Jim Patrick

Frank's reply is the first thing to check. The bulb must have ground path from the socket cylinder that holds the bulb, that socket should be a firm fit but allow the adjusting screw on the back of the headlamp bucket to pull or push it to focus the bulb beam.

An illuminated Check lamp is handy and it has a battery powered lamp that will light up to confirm continuity. Clip on the metal socket, and then on a clean ground, like a shiny nut or bolt somewhere. That will check the socket can be grounded. If the lamp won't burn, then the socket is riding on painted surface, the headlamp bucket pad and bolts to the fender and fender bracket to frame are on painted surface. Confirm you have good ground from the socket to the frame, where the neg. (-) 6v battery is connected.



Be sure the wiring connections with the plug are engaged, and the posts on the socket are engaged with the plug contacts.

You can also check the switch to confirm it is working to switch on the lamps with that test lamp.

As a matter of course these days, my auto elec. son solders a short lead from the bulb socket to one of the rivet heads in the light bucket. This will effectively ground the bulb/socket and guarantees lights of the same intensity.

Allan from down under.

Bruce,
As others have already advised, it is most likely a grounding issue. Without tearing anything apart, I would start with a test light at the terminal block on the firewall. If the test light shows power for bright, dim, and tail it will confirm the switch is good and the wiring to that point is good and that you most likely have a grounding problem. Ford painting methods left a rather thin coat of paint on the finished part, thin enough to easily be scratched and rubbed off during assembly to give a decent ground. During a restoration the paint is generally rather thick to cover small dings and pits, it may look great, but electrically insulates everything. If the problem is grounding you will need to remove parts, sand some paint off the mating surfaces from the frame, to the fender, to the headlight bar, to the headlight bucket, to the plug socket to get bare metal to bare metal contract, and to keep it from rusting and loosing your ground again, coat all the bare spots with dialectic grease.

Jeff

[Bruce I'll give you a call. As others my first indication for head lights not working was a grounding problem. But when you added that your tail light didn't work too I wondered about your ignition switch. I did a search on you previous postings and found this picture, I assume that you restored the switch your self. --
So the first thing to do is to test it for continuity to rule it out as a possible cause. If it checks out then the easiest next step is checking the taillight for any grounding issues.
The tracking marks on the backing plate would indicate that the outer ring contacts heights are correct but just the same... when turning the handle to ON and DIM you should feel the contacts settling into the indent, dimple, positions (not the brass contact points). If you don't fell that then it is likely that the outer ring contacts are not making good contact with the brass positions. In this case it may be necessary (not always advised) to bend them up slightly.
A usually cause for bad contacts is a warped backing plate. The bottom surface of the backing plate needs to be relatively flat (light sand should take care of that).
--
The ignition switch is two switches in one. The key selects the power source for the coils/engine, while the handle selects the the lighting.
So in testing the switch when the handle is turned to one of the positions shown, there should only be continuity across any of the corresponding green locations. --

I had problems with my right headlight. It only would work when it felt like it. I decided the bulb socket wasn't grounding to the shell, but in fact the whole light assembly was not grounding to the fender brace. I finally used a file as suggested above and wrapped some bare stranded copper wire around the bolt. This gave a good solid ground and eliminated the problem. Newly painted parts can be expected to interfere with grounding. Powder coating is even worse than paint. Rust is also an effective insulator. A poor ground can affect most any electrical item on the car. Headlights can fail to ground at their mounting point and at the bulb socket, and fenders and other parts can be bolted tightly to the body and frame and still fail to have a good electrical ground.

If your car will run on battery, it confirms the battery voltage is reaching the switch. And since all lights including tail light don't work, My first suspicion would be the switch is not working correctly or the wires leading out of the switch are not working. The next thing to check would be the terminal block. When you turn on the switch is the electricity reaching the terminal block. From there check to each light.
Norm

Thanks everyone for the comments and recommendations. I found that headlight bucket isn't grounded to the frame, so I put a temporary wire between a bolt on the spring and the bucket. Light works fine. I will follow recommendations on how to get the bucket grounded.

I found that the tail light bulb was bad, so replaced it and now I have tail light!

Glad you’re on the right track about your grounding issue. I think I would star with the switch first to Eliminate that first. Might remove the battery ground connection to the frame. Sand clean the area where the cable attaches to. Your grounding starts with a good battery ground.

Good job. Model T’s pose many unique problems. Now you know what to look for… at least on this problem. Jim Patrick

The ground terminal was only required if you were using a real Magneto for the sparks.

Those Magnetos require a ground to turn off the sparks and stop the engine.

Not many are in use anymore, but some switches still have the ground terminal.