1957 Headlight Switch troubleshooting High/Low and Dash lights

[jams4546]

We are trying to figure out why the 'high-low' switch does not work for our 57 Thunderbird. The headlights are good and checked. We purchased a new 'high-low' switch (on floor board). Wiring seems good. Anyone have any thoughts on what is the problem that we are overlooking ?? Really getting frustrating !! Thanks !

 

[jack-in-sac]

First you do not say whether you have any headlights at all either high or low. If none I would look at the headlight switch. Second if you at least have high or low I would check the to be sure you have power at the dimmer switch. Next go from where it is "hot" to where you do not have electricity. Electricity is like plumbing in the regard that you must not have any leaks as in grounds and that it needs to be able to flow through the wires like water through the pipes.
In short, pun intended, start where you know it is hot and go from there to where you no longer have electrical power. Every junction block and every connection is potential problem as every pass through where metal can contact the wiring.

 

[paul5456]

I take it that the new switch does not work either??

Put a test light on the switch terminals going to the lights to see if you got power going out of the switch

 

[57tbird57]

While on the subject: my dimmer switch turns my dash lights on and off. When i turn the brights on, i have dash lights, but no rehostate function. Switch to dim and dash lights go out. All other lights work as they should. Any thoughts on this one would be appreciated.

 

[jimntempe]

While on the subject: my dimmer switch turns my dash lights on and off. When i turn the brights on, i have dash lights, but no rehostate function. Switch to dim and dash lights go out. All other lights work as they should. Any thoughts on this one would be appreciated.

The dash lights are supposed to be powered from a terminal on the headlight switch after the power goes thru the rheostat on the headlight switch. Those rheostats often go bad so my guess is someone disconnected the wire (or worse cut it somewhere) from the headlight switch and for some unknown reason connected it to one of the wires from the dimmer switch, the highbeam wire it would seem. So I would start looking for an oddball wire connected to the wire that come from the highbeam switch that feeds the highbeams. Wiring shortcuts done by hobbyist on these old cars can be a nightmare to sort out. It's also possible they never disconnected (or cut) the wire from the rheostat but just left it there and spliced into it with a connection from the highbeam.

 

[jack-in-sac]

The dash lights are supposed to be powered from a terminal on the headlight switch after the power goes thru the rheostat on the headlight switch. Those rheostats often go bad so my guess is someone disconnected the wire (or worse cut it somewhere) from the headlight switch and for some unknown reason connected it to one of the wires from the dimmer switch, the highbeam wire it would seem. So I would start looking for an oddball wire connected to the wire that come from the highbeam switch that feeds the highbeams. Wiring shortcuts done by hobbyist on these old cars can be a nightmare to sort out. It's also possible they never disconnected (or cut) the wire from the rheostat but just left it there and spliced into it with a connection from the highbeam.

On the subject of the rheostat dimmer which is a wire wound resistor. Yes they do die as they are a thin gauge wire with electricity running through them. I ran out of finding suitable switches to cannibalize. I also used to buy headlight switches for '56 Ford pickups as the switch is the same. I chose not to replace the headlight switch every time this happened on my old fords as the price of switches increased. I use a jumper clip to energize the dash lights when the headlights are "on". I can't dim the dash lights, they are full on when in use. This is not a problem for me.

 

[doug7740]

If the dash lights do not work, make sure to rotate the headlight switch while checking. If the dash lights now light, then switch and rheostat are good. If they still do not light, check for continuity between terminal R (black wire) and terminal I (blue wire with red band) while rotating the rheostat. If no continuity, replace the switch or the rheostat if you can find one. On my Thunderbird the rheostat has been eliminated with a jumper wire between R and I terminals.

When you pull the headlight switch knob to the parking light or head light positions, you make an internal connection between the A and R terminals.



The following is the headlight switch terminal wiring on my 1955 Thunderbird.

B - Battery

B Wires

1. Yellow – Starter relay terminal battery supply
2. Yellow - B terminal of the ignition switch
3. Blue/White – Cigar lighter

A - Internal connection from terminal B

A Wires

1. Green – Stop lamp switch
2. Blue/Black – Clock

R - Connected to the A terminal in the park or headlight positions

R Wire

1. Black – Tail and license lights

D – Connected to the B terminal through the 9 amp fuse that is mounted on the back of the head light switch

D Wires

1. Green/Yellow – Left door jamb switch for the interior light
2. Green/Yellow – Right door jamb switch for the interior light

P – Connected to R and A terminals in the park position

P Wire

1. Black/Yellow – Parking lights

H – Connected to R and A terminals in the headlight position

H Wire

1. Red/Yellow - Headlights (to the dimmer switch on the floor)

I – Connected to R through the rheostat (resistance changes as the dimmer knob is rotated)

I Wire

1. Blue/Red – Instrument panel lights

Hope this helps.

doug7740
1955 Thunderbird Blue

 

[Ward 57]

On the subject of the rheostat dimmer which is a wire wound resistor. Yes they do die as they are a thin gauge wire with electricity running through them. I ran out of finding suitable switches to cannibalize. I also used to buy headlight switches for '56 Ford pickups as the switch is the same. I chose not to replace the headlight switch every time this happened on my old fords as the price of switches increased. I use a jumper clip to energize the dash lights when the headlights are "on". I can't dim the dash lights, they are full on when in use. This is not a problem for me.

I found a simple solution to the rheostat issue. I replaced mine and then another year or so it quit working again 20-30 + years ago. I sprayed some penetration oil on it and it works again. Those coils get corroded and dirty fast.

 

[Walt57Yuma]

If the dash lights do not work, make sure to rotate the headlight switch while checking. If the dash lights now light, then switch and rheostat are good. If they still do not light, check for continuity between terminal R (black wire) and terminal I (blue wire with red band) while rotating the rheostat. If no continuity, replace the switch or the rheostat if you can find one. On my Thunderbird the rheostat has been eliminated with a jumper wire between R and I terminals.

When you pull the headlight switch knob to the parking light or head light positions, you make an internal connection between the A and R terminals.

View attachment 21744

The following is the headlight switch terminal wiring on my 1955 Thunderbird.

B - Battery

B Wires

1. Yellow – Starter relay terminal battery supply
2. Yellow - B terminal of the ignition switch
3. Blue/White – Cigar lighter

A - Internal connection from terminal B

A Wires

1. Green – Stop lamp switch
2. Blue/Black – Clock

R - Connected to the A terminal in the park or headlight positions

R Wire

1. Black – Tail and license lights

D – Connected to the B terminal through the 9 amp fuse that is mounted on the back of the head light switch

D Wires

1. Green/Yellow – Left door jamb switch for the interior light
2. Green/Yellow – Right door jamb switch for the interior light

P – Connected to R and A terminals in the park position

P Wire

1. Black/Yellow – Parking lights

H – Connected to R and A terminals in the headlight position

H Wire

1. Red/Yellow - Headlights (to the dimmer switch on the floor)

I – Connected to R through the rheostat (resistance changes as the dimmer knob is rotated)

I Wire

1. Blue/Red – Instrument panel lights

Hope this helps.

doug7740
1955 Thunderbird Blue

Doug, Your headlight switch wiring description was very helpful. I just replaced the switch but still no instrument panel lights. My head, tail and parking lights work, as well as the radio. It is my understanding that 12v power should be present on the “H” terminal Which in turn feeds the resistive dimmer switch going to instrument lights, correct? Do you or anyone other happen to know where that H terminal power comes from. It appears the previous owner may have monkeyed with the original wiring.
waltyuma57

 

[doug7740]

The “H” terminal of the headlight switch supplies voltage to the foot dimmer switch on the floor and 12 volts is present at the “H” terminal when the headlight switch is in the headlight position.

If you do not have dash lights you need to look at the “I” terminal of the headlight switch. The dash lights are turned on by pulling out the headlight switch. If your dash lights do not work the problem may be that your switch has developed a thin layer of oxidation. The dash lights are turned on when a small spring tip comes in contact with the inner mechanism of the switch. As oxidation builds up on the spring contact, a failure to make contact can result. No contact means no dash lights.

doug7740
1955 Thunderbird Blue

 

[Walt57Yuma]

Here is a picture of the worn out headlight switchI just replaced. As you can see the “I” contact tab was trying to make contact with the spring resistor but, the spring had actually broken. This may be a good example as to what can go wrong with the dimmer portion of this switch. I intend to take dimmer resistance readings on the new switch to see if it’s working ok.
waltyuma57

 

[Ward 57]

The rheostat can be bypassed but you loose the ability dim the dash lights.

 

[doug7740]

Even though Ward didn't tell you how to do it, I believe this is what he is referring to.

doug7740
1955 Thunderbird Blue

 

[Walt57Yuma]

Even though Ward didn't tell you how to do it, I believe this is what he is referring to.

doug7740
1955 Thunderbird Blue

View attachment 25814

All of this information you guys are providing is helping to solve this puzzle on my failed instrument lights. So here is where I am now, but still no instrument lights: First, I removed the old Headlight Switch HS), it was truly bad, see previous pics.

I completely took the HS out of the circuit than located the “I“ wire (Bi-R) and connected it to a independent +12 vdc side of a power supply (first, I checked all the bulbs—all good), pulled one bulb and ran the 12vdc negative to its socket frame. The bulb lights as do all the other instrument lights, I did the same for the rest of instrument lights, all light. However, when I reinserted each bulb into the instrument panel and moved the negative 12vdc independent power supply to the dash metal ground no lights again. So, my question: is the instrument panel solely dependent on the bolt/screws for grounding Or is there a wire feed to insure a good ground.

A bit more info others might find of valve when debugging the HS; I tested the new switches rheostat’s ohms range by placing ohm meter from the R to I and I to Ground. The results are a range of 6 to 18 ohms by rotating the switch knob. Using ohms law I=V/R you get a current range of 0.667 to 2.0 amps. Which seems spot on to dim and operate the instrument lights correctly. In addition, I took notice that the HS connectors are actually labeled in a manner to tell you pretty much what wires go where by their first letter representing function, as follows:

B=Battery Positive
D= Dome Light
P= Parking Lights
H= High-beam dimmer switch
I= Instrument lights
R= Rear Tail lights
A= Stop lights (This one does not track?)
The HS metal case is ground.

waltyuma57

 

[SWinner]

This may not solve your problem if none of your dash lights are working, but on my 56 I had some bulbs that were intermittent or not working at all. I found that the fault was a poor ground at the faulty bulbs. To resolve this, I ran a dedicated ground wire to the heater control switch, radio, clock, tach and the back of the speedometer. I terminated this wire to the same screw as the engine block to firewall ground. The other dash bulbs, I removed the bulb socket and sanded the inside of the socket hole to remove any rust or paint that was causing a high resistance. This restored a proper ground to the bulbs.

Hope this helps,
Steve

 

[Ward 57]

Even though Ward didn't tell you how to do it, I believe this is what he is referring to.

doug7740
1955 Thunderbird Blue

View attachment 25814

A jumper wire would work also if you are not handy with a soldering iron.

This may not solve your problem if none of your dash lights are working, but on my 56 I had some bulbs that were intermittent or not working at all. I found that the fault was a poor ground at the faulty bulbs. To resolve this, I ran a dedicated ground wire to the heater control switch, radio, clock, tach and the back of the speedometer. I terminated this wire to the same screw as the engine block to firewall ground. The other dash bulbs, I removed the bulb socket and sanded the inside of the socket hole to remove any rust or paint that was causing a high resistance. This restored a proper ground to the bulbs.

Hope this helps,
Steve

I can't state enough about di-electric grease. I had issues with my map light resistance. Smeared the bulb, base and socket. It's never been brighter before. There are so many different metals involved galvanic corrosion is your issue.

 

[Walt57Yuma]

Update on getting the dash board instruments lighting working;
After installing the new Headlight Switch, it did not solve the no instrument light issue. To my amazement the new switch was defective right out of the Chinese box,ugh! Another one was ordered and installed. During my further debug, I took notice of three dash wires where the insulation was gone and one was arching if pulled (see pic). I have replaced all such wiring. I was still having a weak ground situation so sanded most connections and applied di-electric grease as you all suggested. I also replaced three burned out T8-57 light bulbs. after tackling this multi-issue situation. I now have instrument light!
By the way, I pulled out the seat so I could fit under the dash.
Thank to all of your suggestions that got me through this difficult repair.
Walt57Yuma