I have a 1964 convertible. The headlight warning lamp in the dash does not illuminate. Can I put a probe in the bulkhead connector where the wire goes thru that feeds the limit switches, ground it, and with the headlight switch on see if the lamp is the problem? Or would connecting a jumper on each limit switch give me the same result? I would like to be sure it is the lamp before I crawl under the dash.

Thanks, Paul

 

Short answer, yes you can. It's the top right pin (as you look from the front of the car) on the right hand (as you look from the FRONT of the car) connector. It's actually called the left hand connector, but the picture shows the pin with the arrow.
Since I can't sleep, here's a longer answer to explain how it works (or doesn't)



The light blue wire that supplies voltage to the bulb connects to the headlight switch on the same pin as the headlight feed to the dimmer switch on the floor. One wire goes to the dimmer and one to the bulb, then the gy/black wire goes to the pin you need to short as shown above. That gy/black wire could be broken loose from the headlight swtich or from the bulb, or the bulb not inserted into the cluster to get a ground. Grounding the pin shown will tell you that if it still doesn't light, it's between the connector and the bulb in the cluster.

The switches on the headlight motors are unique in that they are normally closed (shorted) to ground throughout the entire movement of the motors. Then when BOTH buckets are rolled far enough to open BOTH switches, the ground is removed from the circuit turning off the light. So if the problem is up front, it can only be if the gy/black wire shown with the double wire connection has a broken wire before it gets to the split. Just being unplugged won't cause the lamp not to work, the gy/black wire coming to the driver's side bucket switch has to be broken somewhere between the bulkhead connector and the point shown since the switches are wired in series and the other switch would still illuminate the light.


In order of likelihood of what your problem will be:
By far most likely, bad bulb.
BOTH black wires or/and both gy/black wires disconnected at headlamp bucket warning switches (easiest to check and I've seen it on many cars where they were disconnected to keep the light from coming on due to switch misadjustment. You can also short either of those black wires on the warning switches for the buckets to ground and turn on the lights and verify your wiring all the way from the dash to the buckets if the light works.) I would check those two black wire connectors BEFORE anything else. You may find all the wires disconnected from the switches. Remember, the lamp will still light with only one side of the car bucket wires connected, so both would have to be disconnected.
Bulb not inserted in cluster hole to provide ground.
Wire between headlight switch and bulb broken. (lt.blue)
Wire between bulb and bulkhead connector broken (gy/black)
Corroded pin in bulkhead connector (shown in first picture)
Wire broken between bulkhead connector and driver's side bucket tell switch before split at bucket switch.


Here's a picture of the two contacts on each switch that must be connected for warning lamp to illuminate.

 

PS I see you've been a member for 15 years and have 9 posts. I don't know if that's a record, but it has to be close. You don't often ask for help, so I wanted to be sure you got all the information you needed. If not, let me know.

 

Thanks for your quick reply. The information and the wiring diagrams clearly explains how the circuit works, and the most logical way to find the problem. I will dig into it and let you know what I find.
Thanks,
Paul

 

Any change yet?

 

I was finally able to dig into it last nght. I grounded the bulkhead terminal and still no light. I disconnected the battery, and then loosened the cables connected to the bottom of the cluster, and dropped the steering column a bit. I took out the 1/4x20 scews and inserted some longer ones so I was able to move the cluster forward some. I got the bulb out, and it was bad. Amazingly, over the years I accumulated a couple of #257 bulbs, so I had a replacement.
I really appreciate your help. Working on my back behind the cluster is not FUN!! (LOL)