I would like to thank you in advance for any advice you can render. On my '48 Ford I've got a problem where the tail and instrument lights come with the light switch in the park position. When I pull the knob to the head light position it loses tail and instrument lights, but the head lights will come on. The dimmer switch will also operate in both low and high beam. Can it be the light switch is no good?
Electric problem with tail lights
- Thread starter Sal
- Start date
Bolts
Well-known member
Possibly first you can run down the wiring to make sure it's wired correctly before removing the switch. Stock switch has a little slot for a small screwdriver to be inserted in so that the switch knob and shaft will come out so you can remove the nut and take the switch out. Not hard to do once you know how. Problem is the slot is on top and it's a little hard to reach.
Attachments
flatheadmurre
Well-known member
Lots of different things that could be wrong but in or around the switch.
Wiring could be wrong but if it worked before thats not it.
Wornout or corroded contacts inside switch...spray with contactspray and wiggle the switch and se if you can excersise the switch to take away oxide.
Bad connection between rivets and contacts outside switch.
Check for loose rivets or signs of oxide.
Wiring could be wrong but if it worked before thats not it.
Wornout or corroded contacts inside switch...spray with contactspray and wiggle the switch and se if you can excersise the switch to take away oxide.
Bad connection between rivets and contacts outside switch.
Check for loose rivets or signs of oxide.
Bruce Lancaster
Member Emeritus
'48 Ford switches are very durable and generally fail just from dirt.
Remove the thing as noted above (this is a bit difficult the first time) and let it hang down on the wires so you can check wiring against the letters in plastic plate indicating proper locations.
The remove wiring, gently and carefully bend back the tabs, and remove plastic from metal body. Do this over a piece of cloth and lay the pieces inside out carefully...if you drop things you'll be in trouble fast. Swizzle the parts in thinner or whatever you use and brush away the decades of filth. Polish the brass contacts and carefully reassemble
with light grease on everything.
Bend tabs back carefully so the next overhaul won't be a problem for your grandchildren.
Remove the thing as noted above (this is a bit difficult the first time) and let it hang down on the wires so you can check wiring against the letters in plastic plate indicating proper locations.
The remove wiring, gently and carefully bend back the tabs, and remove plastic from metal body. Do this over a piece of cloth and lay the pieces inside out carefully...if you drop things you'll be in trouble fast. Swizzle the parts in thinner or whatever you use and brush away the decades of filth. Polish the brass contacts and carefully reassemble
with light grease on everything.
Bend tabs back carefully so the next overhaul won't be a problem for your grandchildren.
Bolts
Well-known member
Sal,
Sounds like the switch may be mis-wired. Did it ever work right?
There is a good wiring diagram here.
http://www.vanpeltsales.com/FH_web/...pics/Flathead_Electrical_wiring1946-48car.jpg
If you feel it's necessary to remove the switch, REMEMBER TO DISCONNECT THE BATTERY FIRST.
I can't remember exactly, but when you insert the small screwdriver into the switch slot, I think the knob might need to be pushed in to the off position (possibly the other way around to full on position) and the knob rotated 90 degrees to remove the shaft. Not sure, but try rotating the knob without a lot of force before pulling too hard on the knob while lever is releasing the locking tab.
Bruce Lancaster
Member Emeritus
Another basic thing before you go to work: Unplug the taillights at the first bullet connectors about one foot from the lights and run a jumper wire to them to see if they light up. If they are good THEN tear down the switch and clean it.
You'll need a long wire to the battery hot post, of course, and this could be improvised from a household extension cord, with one person holding prong to battery and another making contact in back with a nail or something shoved into the female end of plug to allow touching the connector.
You'll need a long wire to the battery hot post, of course, and this could be improvised from a household extension cord, with one person holding prong to battery and another making contact in back with a nail or something shoved into the female end of plug to allow touching the connector.
I was going to say the same. Ground faults can drive you nuts!
Drbrown
Well-known member
Sal: Glad you found the problem. For what little this might be worth .... In my '47, the first notch of my dash switch (parking light position) turns on the front parking lights, instrument lights, key light and the tail/trunk/license plate lights" .... this agrees with the wiring diagrams I have.
When I move the dash switch to the second notch (head Light position) the front parking lights go out, the key light goes out, the head lights turn on, and the tail/trunk/license plate lights remain on.
An aside: As a safety feature, the brake lights ALWAYS work. They are "unfused" and wired separately and direct from the battery feed-side of the Circuit Breakers. The pillar and glove box (optional) are wired separately to the Circuit Breakers.
When I move the dash switch to the second notch (head Light position) the front parking lights go out, the key light goes out, the head lights turn on, and the tail/trunk/license plate lights remain on.
An aside: As a safety feature, the brake lights ALWAYS work. They are "unfused" and wired separately and direct from the battery feed-side of the Circuit Breakers. The pillar and glove box (optional) are wired separately to the Circuit Breakers.