36 ford lightswich and starter switch question

[Justin36ford]

I've got a 1936 ford coupe that I've been rebuilding from basically ground up. I am at the point now where I'm trying to sort out the wiring harness. I have an E-Z Wiring 21 harness and am trying to figure out what to do for the light switch as the way the kit is set up for lighting is much different from how the car was from the factory.


The fuse box has separate wiring for the different lights, where the factory light switch on the car seems to have a power in and then junctions the lights all from the switch. So i was planning on running a slightly thicker power wire from the headlight fuse on the fuse box with a larger fuse and then sending that to the light switch. My concern is that the light switch might not be able to handle 12v


Another question I have is the floor starter switch was wired up directly to the alternator and then from the switch to the battery. I have it wired up the same way right now, but before someone had a 35amp alternator running to it, and I have upgraded to a 100amp (I'm hiding a headless sound system behind upholstery). Can that floor switch handle acting as a power block for that amount of amperage or should I route the alternator straight to the battery now and then back to the starter switch?


I'm sorry for any ignorance on these topics as I'm largely self taught, I can update with any pictures requested tomorrow when I go into my shop.

[tubman]

This all depends on what your goal is. If you are building a "Hot Rod", then the stuff you have can probably be made to work. If you are going for anything close to stock, it is totally unsuitable.

What are your intentions?

[Justin36ford]

The car is very much not stock and I think would fall more into the "Hot Rod" category. It has a later model Flathead, juice brakes, chopped, a trunk conversion, among other things. However I would like to use the factory light switch with the steering wheel if at all possible, and the part about the routing of the battery cable to the starter button/switch is more of a safety thing as I don't know if I will burn it up with my current setup.



The site unfortunately won't allow me to upload any pictures at the moment

[Bob C]

The wire from the alternator should go to the battery side of the starter switch.

[TJ]

Justin, here's a suggestion for you. Since you are using a modern wire harness why use a stock 36 switch? An alternative is use a stock GM light switch and put on the stock '36 dash light knob. Then mount the switch in the dash hole that was meant for the stock dash light switch. In addition at some point you may want to change the steering box and you will not have to move the wiring.

[Justin36ford]

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Originally Posted by TJ

Justin, here's a suggestion for you. Since you are using a modern wire harness why use a stock 36 switch? An alternative is use a stock GM light switch and put on the stock '36 dash light knob. Then mount the switch in the dash hole that was meant for the stock dash light switch. In addition at some point you may want to change the steering box and you will not have to move the wiring.

My 36 doesn't have a dash light knob (at least I haven't seen one). The way you select the lighting is on the steering wheel by turning a dial that surrounds the horn button. depending on where you turn it that's what selects park lights/high beams/low beams. The horn rod goes all the way down to the end of the steering box and fits into a switch that has the wiring for all the lights. The option is there to put a switch directly into the dash but I really like the idea of keeping the switch built into the steering wheel itself. It seems i have to post a few more times before I can post pictures, otherwise I would link what it looks like.


edit: When you turn the light switch is turns the whole horn assembly and rod

[Justin36ford]

Originally Posted by Bob C

The wire from the alternator should go to the battery side of the starter switch.

Correct, but before the alternator was only pushing a maximum of 35 amps, and now it can push a maximum of 100 amps. My concern is that under a larger load that might damage the starter switch or in worst case create a fire hazard.

[tubman]

The maximum load put on the starter switch comes from the battery when it is engaged to start the car. 35 or 100 amps from the alternator is nothing compared to that.

You are aware that the actual light switch itself is at the bottom of the steering column, don't you? All of the lighting wires come out from under the steering box rather than from under the dash. I don't know anything about the E-Z-Wiring harness, but I'd bet dollars to doughnuts their harness would take a lot of modification and you might be better off starting from scratch.

[koates]

Hello, I am an auto electrician (old one) and if you have mostly a hot rod and are fitting a modern wiring loom kit it needs to be modified to incorporate the original Ford lighting switch at the bottom of the steering box which includes the high/low beam dip switch. This could be a bit difficult if you are not good at auto electrics and so I would suggest that you find an older auto electrician to help you out. However the power cable into the original headlight switch from the original under dash single fuse would have to be connected into a good power source (fuse box) in your modern loom. All other wires to headlights, tail lights, park lights and dash lights could still connect to the old steering column switch. You would have to also run a separate wire from the tail light terminal on the original switch up to the dash instrument lights. See this on an original wiring diagram for a 1936 Ford. See how you go. Regards, Kevin.

[Justin36ford]

Originally Posted by tubman

The maximum load put on the starter switch comes from the battery when it is engaged to start the car. 35 or 100 amps from the alternator is nothing compared to that.

You are aware that the actual light switch itself is at the bottom of the steering column, don't you? All of the lighting wires come out from under the steering box rather than from under the dash. I don't know anything about the E-Z-Wiring harness, but I'd bet dollars to doughnuts their harness would take a lot of modification and you might be better off starting from scratch.

The load was 35 amps. I have since upgraded the alternator and it is now 100amps coming from the alternator. However I am not sure exactly what the draw is from the battery. But i did look it up and it seems to be around 200-300 amps from a quick google search (it has a 51 mercury Flathead in it)


I am aware that the actual switch is at the base of the steering column, My plan was to unpin all the lighting wires from the fuse box and pin in a larger gauge wire that I run to power the light switch itself.



So lets say I have a 20 amp fuse just for the headlights, a 20 amp fuse just for the taillights, and a 20 amp fuse for the high beams. (I don't have the fuse box in front of me right now, this is just hypothetical). I will remove the fuses for the taillights and the high beams and unpin the wires associated with them. I plan to put in lets say a 40amp fuse into the headlight fuse location, and then run a larger gauge wire out of that pin to the light switch at the base of the steering column to power all the wires that branch off of the switch for their respective lights.

[Justin36ford]

Originally Posted by koates

Hello, I am an auto electrician (old one) and if you have mostly a hot rod and are fitting a modern wiring loom kit it needs to be modified to incorporate the original Ford lighting switch at the bottom of the steering box which includes the high/low beam dip switch. This could be a bit difficult if you are not good at auto electrics and so I would suggest that you find an older auto electrician to help you out. However the power cable into the original headlight switch from the original under dash single fuse would have to be connected into a good power source (fuse box) in your modern loom. All other wires to headlights, tail lights, park lights and dash lights could still connect to the old steering column switch. You would have to also run a separate wire from the tail light terminal on the original switch up to the dash instrument lights. See this on an original wiring diagram for a 1936 Ford. See how you go. Regards, Kevin.

This is great information thank you, My main concern is whether that factory ford light switch at the bottom of the steering box can handle 12v without a voltage reducer

[tubman]

Original 6 volt wiring, if in good shape, should always be more than adequate to carry 12 volts. Given and equal power requirement (watts), it takes half as many amps with 12 volts. Excessive amps are what burn out switches and wires, etc.

[Justin36ford]

Originally Posted by tubman

Original 6 volt wiring, if in good shape, should always be more than adequate to carry 12 volts. Given and equal power requirement (watts), it takes half as many amps with 12 volts. Excessive amps are what burn out switches and wires, etc.

Very good to know, every wire is being replaced, I was just worried about burning out the switch. I've done a decent amount of fabrication and body work, but wiring, beyond audio, is pretty new to me. Luckily I pulled the original harness out that the previous owner modified so I am able to follow that as a guideline while I modernize it. I just didn't like how chopped up it was so I wanted to replace it and go for a nice clean job instead of repurposing the older harness for my needs.

[cas3]

When talking voltage and amps, 6 volts is 1/2 the amps of 12 volts running thru the wire.

Plain talk, if you got 15 amp load in an old 6 volt car, it would probably have 14ga wire.

15 amp load in a 12 volt car would probably have 18ga wire.

So, when converting to 12 volts you are getting 1/2 the amps as a 6 volt system.

in other words the original light switch will get 1/2 the load it was made for.

The need for a 100 amp alt is crazy in my opinion, thats for motorhomes.

Glad you prefer the old switch, it shows good taste IMHO. you will just have to figure out how to hook it all up with a test light or meter. Good luck, lets see the coupe

[Justin36ford]

Originally Posted by cas3

When talking voltage and amps, 6 volts is 1/2 the amps of 12 volts running thru the wire.

Plain talk, if you got 15 amp load in an old 6 volt car, it would probably have 14ga wire.

15 amp load in a 12 volt car would probably have 18ga wire.

So, when converting to 12 volts you are getting 1/2 the amps as a 6 volt system.

in other words the original light switch will get 1/2 the load it was made for.

The need for a 100 amp alt is crazy in my opinion, thats for motorhomes.

Glad you prefer the old switch, it shows good taste IMHO. you will just have to figure out how to hook it all up with a test light or meter. Good luck, lets see the coupe

This is something I didn't realize, and it shows that I need to do some more research on my own. I just assumed that 12v was twice the power of 6v as I've been told (and the previous owner used them) to put voltage reducers going to the gauges to insure that they don't fry.



The 100 amp might not be completely necessary, but I've installed a headless sound system that is going to be hidden behind upholstery to keep a somewhat factory appearance on the interior. The amplifier that I am running is 2000 watt, and the four speakers and one sub I have for the car has the potential to use all of that.



I would love to post some pictures, but I have to reach 10 posts before I can.

[Kurt in NJ]

For the 100 amp alternator you need 100 amp wire between the alternator and battery connection.
Ford used a double belt system for the high amp generator, are you upgrading the belt system to be able to drive that alternator at 100 amps without burning up the belts at maximum output?
What are you going to use for fan?

[Justin36ford]

Originally Posted by Kurt in NJ

For the 100 amp alternator you need 100 amp wire between the alternator and battery connection.
Ford used a double belt system for the high amp generator, are you upgrading the belt system to be able to drive that alternator at 100 amps without burning up the belts at maximum output?
What are you going to use for fan?

This is interesting, I just have a single v belt that goes around the crankshaft, the two water pumps, and the alternator. It was the same setup the previous owner was using with a 35amp alternator. Would the crankshaft not be spinning the belt at the same speed regardless of what size alternator is on the car? I don't know if it makes a difference, but the engine in it is a 51 mercury Flathead built by H&H with a 4" crank



I'm using 4 gauge power wire from the alternator to the starter switch, and from the starter switch to the battery, which according to the alternator manufacturer and the distance that the wire is being ran, is more than adequate

[tubman]

This thread is starting to go off-topic. I'm sure we can help with incorporating the original light switch into a new wiring harness, but there have to be better places to find out about driving 2000 watt stereo systems.

[Justin36ford]

Originally Posted by tubman

This thread is starting to go off-topic. I'm sure we can help with incorporating the original light switch into a new wiring harness, but there have to be better places to find out about driving 2000 watt stereo systems.

Sorry, that wasn't my intention, I was just trying to explain why I was using the high amp alternator.

[cas3]

I aint no durn lectrishon, but heres my take...Ever notice when you turn on your headlights in a modern car, the rpm drops a little? thats the load on the alternator.

So, that rpm drop is with a fully charged battery, maybe a little draw if you just started it, but mainly just the load of the lights being on and using power.

Race cars run no charging system to avoid the power loss.

Now thats in normal mode, fully charged battery, and normal...lets say...60 amp alt.

Now the not normal would be if you had a dead battery, and jumped it or push started it, now that 100 amp alt senses the low battery condition, puts out the full 100 amps, the load on the belt and the wire gauge will be tested to the limit even if briefly