I am installing a new wiring harness in a 1953 M250 Classic. I have upgraded to a 12 v but everything else is original. The new harness came in a box of parts with the truck. It seems like the directions are referring to a different headlight switch then the one I have. Almost like something from a 1956 or something. I am not strong with the electrical side of things and I was wondering if I should change the switch? Would anyone have an easy to follow schematic? Thanks
Electrical question
- Thread starter Stoker280
- Start date
Lawson Cox
Well-known member
I would volunteer an opinion, but I only know that there are two kinds of electricity: the kind that will hurt you and the kind that'll make you hurt yourself.
V8COOPMAN
Well-known member
Not knowing what differences there are in the two switches, I don't have a clue how anyone could help you. If the only BASIC difference in the switches is the voltage rating (6v versus 12v), that in itself is not likely to be a limiting factor. So, if you could maybe post pictures, or possibly what the two switches original applications were, we MIGHT be able to offer SOME advice. Even a somewhat detailed drawing of the two switches may get us going here. DD
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rotorwrench
Well-known member
A circuit breaker only responds to high current draw above its rating. It doesn't care what the voltage is.
Ford of Canada did some things differently than Ford US. I don't know whether the Mercury line even had the same switch to the Ford line but any 6-volt system will function on 12-volts. The wire size is overkill but it will work. Fuses and circuit protectors also remain the same, They're rated for the wire size and not the load.
The 1951 through 1954 F series trucks likely all used the same switch. The switch changed in 1955 and again in 1956 but the two later switches likely only have subtle differences. The instrument lamp dimming rheostat likely changed for 1956 with 12-volts but I know of 55 models that changed over to 12-volt and had no problems with the switch.
I would say check the F100 wiring diagram and see if the wire colors match up to the different circuits. If the harness matches up in colors then it can be made to work. A lot of different companies have fabricated new harnesses over the years. Some are good and some are not so good. If it fits and functions then it's usable. If not then you will pull hairs that you would likely like to keep. Here is a link to a thread that has a diagram for the F100. It should match all of the F or M series pickups for that year but a person has to check it and see for sure.
https://fordbarn.com/forum/showthread.php?p=1281165
Ford of Canada did some things differently than Ford US. I don't know whether the Mercury line even had the same switch to the Ford line but any 6-volt system will function on 12-volts. The wire size is overkill but it will work. Fuses and circuit protectors also remain the same, They're rated for the wire size and not the load.
The 1951 through 1954 F series trucks likely all used the same switch. The switch changed in 1955 and again in 1956 but the two later switches likely only have subtle differences. The instrument lamp dimming rheostat likely changed for 1956 with 12-volts but I know of 55 models that changed over to 12-volt and had no problems with the switch.
I would say check the F100 wiring diagram and see if the wire colors match up to the different circuits. If the harness matches up in colors then it can be made to work. A lot of different companies have fabricated new harnesses over the years. Some are good and some are not so good. If it fits and functions then it's usable. If not then you will pull hairs that you would likely like to keep. Here is a link to a thread that has a diagram for the F100. It should match all of the F or M series pickups for that year but a person has to check it and see for sure.
https://fordbarn.com/forum/showthread.php?p=1281165
paul2748
Well-known member
Is the difference only the position of the studs on the back? Recently I came across some differences in the positions on another Ford car ignition switches that I never ran across before.
rotorwrench
Well-known member
I would recommend the solid state constant voltage regulators or runtz type CVRs for each affected gauge rather than use an old style chopper CVR for the whole power circuit. Those things make the instrument needles move around a lot more than they need to. The little runtz type CVRs are available from a lot of sources and there are even U-Tube videos on how to fabricate your own. A resistor makes heat and robs the system of power. A dropping resistor needs to be protected from anything that can melt or catch fire.
Ford Used the chopper type constant voltage regulators from 1957 well up into the 60s since a lot of instruments were made to function on voltages lower than 14-volts. The lower the voltage, the less chance of problems was likely what engineers had in mind. I had an old 64 T-bird for many years and the gauges always wandered around in service. Those old CVRs didn't really keep the voltage constant at all. It just fooled the loads into feeling the voltage was constant.
Ford Used the chopper type constant voltage regulators from 1957 well up into the 60s since a lot of instruments were made to function on voltages lower than 14-volts. The lower the voltage, the less chance of problems was likely what engineers had in mind. I had an old 64 T-bird for many years and the gauges always wandered around in service. Those old CVRs didn't really keep the voltage constant at all. It just fooled the loads into feeling the voltage was constant.
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wga
Well-known member
Make your life easy and use one of these. I have one installed for about 15 years.
All solid state stuff. Easy to install, run the 12V in and 6V constant voltage on the output. You can run 12V bulbs on the gauges too.
https://www.ronfrancis.com/product/159
Check your wiring diagram regarding the headlight switch. Power comes in on the
fuse side.
What about turn signals?
All solid state stuff. Easy to install, run the 12V in and 6V constant voltage on the output. You can run 12V bulbs on the gauges too.
https://www.ronfrancis.com/product/159
Check your wiring diagram regarding the headlight switch. Power comes in on the
fuse side.
What about turn signals?
Frank Miller
Well-known member
I believe the person was referring to a 12 volt system having a lower current rated circuit breaker for 12 volts because it only draws half as much current. It is possible you might not have the correct overload protection when switching voltages. If you have a dead short they all will work fine.
rotorwrench
Well-known member
You can use a smaller fuse on a circuit than what the conductor wire is rated for but you can't use a larger fuse rating on that circuit or the wire may not carry that rated load. Fuses are always rated for the gauge of wire being utilized. I use a circuit protection rating chart in the FAA Advisory Circular AC43.13-1B chapter 11 to fabricate circuits. The SAE follows the same process. The circuit protector is always sized to protect the current rating of the wire.
The average 6-volt circuit uses a #16 AWG conductor wire while the average 12-volt system circuit can use the smaller #18 AWG conductor wire to do the same function. With higher voltage there is less worry about resistance in the conductor so less current is drawn on the average circuit's load with a higher voltage.
The average 6-volt circuit uses a #16 AWG conductor wire while the average 12-volt system circuit can use the smaller #18 AWG conductor wire to do the same function. With higher voltage there is less worry about resistance in the conductor so less current is drawn on the average circuit's load with a higher voltage.