1941 headlight dimmer switch wiring

[hueyhoolihan]

while installing new headlight bulbs (standard 7" sealed beam H4 connectors) i ran into a situation with the wiring that has me a bit confused.

it seems that when the headlight switch is on and the dimmer switch is set to dim, that as expected, the dim wire in the headlight bucket's H4 connector is hot and that the one for the bright wire is not. but when i push the dimmer switch for the bright lights i'm getting current to BOTH the bright wire AND the dim wire at the same time! can this be right? and so am worried about too much heat, current and/or premature failure.

i've verified that this is occurring on both right and left side headlight H4 connectors. i've even removed the raw wires from the connectors to eliminate a possible short in the connectors

to verify that my concern was justified, i immediately confirmed, using another vehicle i own, that the dimmer switch and circuitry to the H4 connector worked as i assumed it did and that the two circuits (dim and bright) worked independently of one another and were mutually exclusive. my research shows that the 1941 ford's should be no different.

a bit puzzled, wondering if there is/was some sort of 6v-generator-dependent-home-brewed-attempt to increase brightness that might be in play here. or maybe even an aftermarket dimmer switch that is/was purposely designed to make this happen...possibly?

i really don't want to have to crawl under the car and try to access the dimmer switch (which is impossible for me, alone, to remove from the floorboard, seeing as how it involves two bolts from the floorboard side and two nuts from underneath the car that i can't even see or touch) with my multimeter to verify that i'm getting mutually exclusive current from the high and low beam connectors.

[hueyhoolihan]

...

[hueyhoolihan]

called vendor that sold me the lights. said that BOTH the high and low beam connectors on an H4 connector should be hot when the dimmer switch is set to high beams.

...now thoroughly confused, as all internet information i've found is unanimous in that the dimmer switches provides power to EITHER the low beam prong on the H4 connector or the high beam, but never both.

so now i have to first sort out how it should be and then sort out if it is wired that way or not. "...one step forward..."

and on the box it says, "Plug and Play!". yea, right.

[Ggmac]

No nuts on the back side of the switch . It threaded .

[hueyhoolihan]

Originally Posted by Ggmac

No nuts on the back side of the switch . It threaded .

excellent, that's good news!

i attempted to remove the slot headed screws and they seemed to be turning as if there were nuts on the other side. but if they are just bolts screwed into the dimmer's housing, that would be helpful, as i can get a look at the back. although i'm pretty sure from what i can feel when underneath the car, as it's not visible, it's probably just a male three pronged H4 connector.

thanks.

[hueyhoolihan]

Sponsored Links (Register now to hide all advertisements)

,,,

[Ggmac]

If original, its a soldered connection with the wires and having bullet connectors on there ends .
Don’t forget many , many hands have been on these old cars , many parts have been changed , sometimes correctly, sometimes not . They used what was on hand, especially towards the end of its life .
You’re still 6 volt pos ground, have you plugged in your old headlights to see if both elements come on ?
The hi beam switch is a simple switch that gets a lot of trash and water near it . I’ve gotten good results by simply using my foot to push the switch rapidly many times with some good pressure. Then check the voltage again ,

[hueyhoolihan]

Originally Posted by Ggmac

If original, its a soldered connection with the wires and having bullet connectors on there ends .
Don’t forget many , many hands have been on these old cars , many parts have been changed , sometimes correctly, sometimes not . They used what was on hand, especially towards the end of its life .
You’re still 6 volt pos ground, have you plugged in your old headlights to see if both elements come on ?
The hi beam switch is a simple switch that gets a lot of trash and water near it . I’ve gotten good results by simply using my foot to push the switch rapidly many times with some good pressure. Then check the voltage again ,

thanks,
i've done all of the above and more.

as you know, the floor-mounted dimmer is a toggle switch with three terminals. one input terminal and two output terminals. my confusion is with the two output terminals. and the question is: are the two output terminals ever supposed to be hot at the same time?

and it appears that no one knows. neither the internet nor the manufacturer. or maybe i should say that everyone knows, but they don't agree, eh?

[Kube]

Originally Posted by hueyhoolihan

thanks,
i've done all of the above and more.

as you know, the floor-mounted dimmer is a toggle switch with three terminals. one input terminal and two output terminals. my confusion is with the two output terminals. and the question is: are the two output terminals ever supposed to be hot at the same time?

and it appears that no one knows. neither the internet nor the manufacturer. or maybe i should say that everyone knows, but they don't agree, eh?

Hey, just wondering... are you the same hueyhoolihan that was giving me crap on Bring A Trailer (40 coupe) a few weeks ago?

[Bob C]

It is the position of the filament in relation to the reflector that determines high and low beam. The schematic shows the dimmer switch is either high or low not both.

[petehoovie]

Originally Posted by Bob C

It is the position of the filament in relation to the reflector that determines high and low beam. The schematic shows the dimmer switch is either high or low not both.

[hueyhoolihan]

Originally Posted by Bob C

It is the position of the filament in relation to the reflector that determines high and low beam. The schematic shows the dimmer switch is either high or low not both.

ya, that's what i thought...doesn't seem to be consensus does there? as everything i can find on the net says it's an either or thing, but the manufacturer of the bulbs i'm putting in says he's never heard of anything other than one or both.

anyway, i simply put the bulbs in they way my car's dimmer works and works with one hot wire or both wires hot.

[koates]

Well I have been an auto electrician for sixty plus years and never heard of or come across a dimmer or dipper switch that brings on both high and low filaments when set for the high beam position. To clarify the switch places power to either low beam OR high beam. That is a standard set up for all makes and models of vehicles since the 1920s. There are some exceptions in the early days but not in the 1940s. You need to get that switch out from where it is mounted and test it . I have come across some sealed beam units and bulbs where the filaments themselves were touching together. A wiring fault is not out of the question, but it would likely cause both filaments to come on in both switch positions. Regards, Kevin.

[hueyhoolihan]

Originally Posted by koates

Well I have been an auto electrician for sixty plus years and never heard of or come across a dimmer or dipper switch that brings on both high and low filaments when set for the high beam position. To clarify the switch places power to either low beam OR high beam. That is a standard set up for all makes and models of vehicles since the 1920s. There are some exceptions in the early days but not in the 1940s. You need to get that switch out from where it is mounted and test it . I have come across some sealed beam units and bulbs where the filaments themselves were touching together. A wiring fault is not out of the question, but it would likely cause both filaments to come on in both switch positions. Regards, Kevin.

thanks...

yes, it surely would, i would think. but the manufacturer of the headlights i bought swears he's never heard of anything but both wires hot when on the high beams. *headscratch*

i will say that in all the years of automobile forum activity i've participated in, from porsche, to aston, to mg, to jaguar and now to ford, this is the first time i can remember ever having a discussion of the internal circuitry of a headlight dimmer switch.

[tubman]

The headlight coverage would possibly be a bit better if wiring both together. (both high and low patterns when on high beams). I believe that would be offset by a much shorter service life (because of the excess heat). This is probably true for incandescent lights, but might not effect LED's. Could this be a wiring change driven by technology?

[Terry,OH]

The dimmer is bolted to the drivers floor board, just three terminals on the switch. The center terminal is power and the outer are either country or city beam.

[rich b]

What symptoms brought you to be testing this?

[petehoovie]

Originally Posted by Terry,OH

The dimmer is bolted to the drivers floor board, just three terminals on the switch. The center terminal is power and the outer are either country or city beam.

[hueyhoolihan]

Originally Posted by rich b

What symptoms brought you to be testing this?

i was getting what looked like high beam on one light and a low beam on another after installing my new headlights, so i got my multimeter out and discovered that (although not directly related to my problem) i was getting one hot wire from the dimmer switch with the low beam and two hots with the high beam. which i did not expect!

and of course i did a bit of internet research and it was confirmed, almost without exception, that my surprise was warranted. so then called the bulb manufacturer and they disagreed with me and the internet...

and so here we are.

i do not plan on replacing my dimmer switch. and so will live with whatever consequences eventuate, i guess. truth is, i've got bigger and more time critical problems to deal with on the car.

[tubman]

Just a basic question. Are you running LED or incandescent headlights? You've mentioned the "manufacturer of the headlights" a couple of times, which leads me to suspect we may be dealing with something unusual for this forum.