Wiring Question

[Taylormade]

There was little left of the wiring in my 1932 dodge Brothers DL sedan when I got her.  Now I'm ready to rewire the car and have a question for all you wiring gurus out there - electrical systems are not my forte.

 

The car originally came with one of those infamous coil/ignition units that had the ignition key built into the coil.  These are still available, but at $250 I'd rather save a few bucks and use a regular coil, since it's hidden under the dash anyway.  In fact, the car ran on this setup when I first owned it and never gave me any problems.  This is the replacement ignition switch that has always been in the car since I owned it.  It has three terminals, IGN, BAT and STA.  Although I took pretty good notes at the time of disassembly five years ago, I can't locate the one sheet I need - how the switch was wired up.  I have a new Rhode Island Wiring harness, but it is designed for the coil/ignition setup.  So, how do I bypass that and wire it correctly for the current ignition switch?

 

 

The green wire went from the STA post on the key switch to the negative post of the coil.  The wires on other two terminals - your guess is as good as mine.  The switch is a simple on and off - just two positions.

 

Here is the wiring diagram for the original wiring setup.

 

 

 

It's a positive ground car. 

What gauge wire is usually run from the positive terminal of the coil to the distributor on a six volt system?

 

Any help or suggestions greatly appreciated.

 

 

[Friartuck]

This article will be a good start. Don't just crimp the blue ring terminals, but crimp, solder, and cover with shrink tubing. Make sure to use ring terminal sized to the wire and stud size:

http://www.secondchancegarage.com/public2/electrical-connections-1.cfm

 

I think your decision to use a separate coil versus the integrated switch/coil version is fine. One thing less to go wrong.

 

If the switch is just two positions, the starter lead doesn't make sense. One terminal to Battery, one to Ignition, and the 3rd terminal could go to other things that are key controlled (e.g. instrument lights)  I don't see a solenoid for the starter, so perhaps that is foot operated.

 

As for wire gauge for the ignition (coil), use either 12 or 14 gauge. That may sound oversize, but the ignition should have a nice strong source.

[PFitz]

This is a common cure for the old key/coil combo systems and it works well. For less than $50.00 you can buy a new 6 volt coil and the mounting bracket. Plus, it makes trouble-shooting and parts replacement easier and cheaper.

 

The three terminal ignition switches are sorta "two position" in that it will stay in either the "on" or the "off" position. The starter position must have the key turned past the "on" position against spring tension to send power to a starter solenoid in addition to the coil.  When the engine starts and you let go of the key, it springs back to just the on position only sending power to the coil.

 

"Bat" terminal is power to the switch. Ign" terminal is the wire to provide power to the coil. The  "Str" terminal would be a wire to provide power to a starter relay if there is no foot starter switch. These switches also show up in some cars that originally had a foot starter switch that went bad and a new 6 volt starter relay is used instead.

 

FYI, NAPA sells a near duplicate of the early coil brackets when moving the coil to the inside of the firewall, as some auto makers started getting away from those key/coil combos in the early 30's. And new 6 volt starter relays are also available through any autoparts store, for any car that has a bad foot switch.

 

Paul

Edited July 29, 2018 by PFitz (see edit history)

[Friartuck]

The switch described by Paul is a three position switch: OFF-ON-MOMENTARY. The OP said it was a two position, but maybe meant to say three. In that configuration it makes sense for a starter with a solenoid.

[Taylormade]

This was the first car I ever owned.  I bought it when I was in college in 1965.  I sold it to a fraternity brother in 1967, regretted it for 45 years and the bought it back from him in 2013.  It was set up with a separate coil when I first bought it and it always ran fine.  After sitting in a garage since 1970, the wiring was pretty bad, although the car still started and ran when we took it out of the garage.  

 

The car has a foot operated starter which turns over fine with the main wiring harness in place and no wiring under the dash.  So no starter solenoid.  As far as I can determine, the key switch has only two positions, on and off.  When I turn the key on, there is continuity between any two of the three terminals.  With it off, there is no continuity between any terminal.  The car ran with the wires currently attached to the switch.  As I said, the green wire went from the STA terminal to the negative post of the coil.  I still can’t find my notes on where the other four wires went.  There may be an extra wire involved, as the car had an electric fuel pump.

[TerryB]

Can you measure continuity from Batt terminal (as the reference terminal) to the other two first with key off, then with the key on?  It seems from what you have said so far that with the switch in OFF, Batt to Starter is open and Batt to Ignition is open as in no continuity.  With key ON you have continuity to both Starter and Ignition.  Just want to make sure that is the case.

 

With the new harness I suspect there is a battery wire (or two) that wii connect to your Batt terminal of your key and with the present connection of the green wire the car will start.  The ignition connection may have been al electric pump power point.  With a footswitch starter there is no need for a spring loaded ignition switch.  Both my 37 Dodge and 1951 Pontiac, which had a starter button on the dash, only had off and on settings.

[Taylormade]

With the key in the off position, there is no continuity between any of the three terminals.  With the key in the on position, there is continuity from the BAT terminal to the STA terminal.  With the key in the on position, there is continuity from thr BAT terminal to the IGN terminal.  With the key in the on position, there is continuity from the IGN terminal to the SAT terminal.

[JACK M]

Hmm, I am confused about the two "on" positions you refer to.

The STA in this case wont be used as it would go to a solenoid as mentioned. (starter)

You make it sound as if maybe the spring load to the STA isn't there.

But none the less all this switch needs to do is turn things on and off.

So, a power source to the BATT terminal and everything else to the IGN terminal is where I would think.

[Taylormade]

There is no spring load on the key switch.  It is either on or off.  I know what your talking about - turn the key past the on position to power the solenoid and engage the starter, then it springs back to the on position when you let off the key..  This switch does not have the momentary feature, believe me, it is either on or off.  It appears when it’s on, all terminals are connected.  Why it has three terminals is a mystery to me, unless the switch might overheat if all the wires went to one terminal.  I know the switch works, because it operated fine in the car before it was rewired and I’d like to use it as it uses the original DB key.  If the key switch had the momentary STA isolation only when turned past the on position, the the continuity to the STA terminal would only happen in this mode.  But when I test the switch, it will not turn past the on position, it just stops, no spring, no spring back. And in that position, without me touching the key all terminals are live.

 

In the wiring diagram, one large  wire runs from the starter to the ammeter to the simple terminal, and the other large wire runs fron the generator to the ammeter to the double terminal with the brass fuse extension, which is exactly how my new harness is designed.  Everything else on the new harness fits as it should.  The fly in the ointment, the original coil/switch, has three terminals.  One wire goes from the double terminal (before the fuse) to the negative terminal on the coil/switch.  One wire goes from the positive coil/switch to the distributor.  A third wire goes from the fuel gauge to the third, unnamed terminal on the coil/switch.  Now I just have to make the correct connection with a separate switch and coil - those three wires which originally went directly to the coil/switch.

Edited July 31, 2018 by Taylormade (see edit history)

[TerryB]

3 hours ago, Taylormade said:

With the key in the off position, there is no continuity between any of the three terminals.  With the key in the on position, there is continuity from the BAT terminal to the STA terminal.  With the key in the on position, there is continuity from thr BAT terminal to the IGN terminal.  With the key in the on position, there is continuity from the IGN terminal to the SAT terminal.

So you have a Battery terminal on the switch that can have the battery voltage wire or wires connected to it from the car’s harness.  When the key is in the OFF position no battery voltage will be present on the other two terminals.  When the key is ON, those two terminals will have battery voltage.  You should be able to choose one of those two ON terminals to send power to the coil.  The other terminal should have a cover over it if it’s not used so you don’t accidentally touch it and make sparks.  If you do choose to power something else from the second ON terminal, you may want to use an in-line fuse with it to protect the item receiving power and to protect your wiring harness. 

Terry

[Taylormade]

I’m curious why there is a third terminal on the original coil/switch.  This takes a wire that runs to the fuel gauge.  Then the other wire on the fuel gauge goes to the sending unit on the tank.  Why wouldn’t the fuel gauge just be powered from the ammeter like the lights and accessories?

 

I am thinking I should take the wire that went from the non-fused terminal on the double ammeter terminal that went to the negative terminal on the original coil/switch, and now connect it to the ING terminal on the replacement switch.  Then run a wire from the BAT terminal to the negative terminal of the coil.  This would power the coil and allow the car to run.

 

Do you think I should hook the fuel gauge to the STA terminal to power it, since turning the key powers both the STA and BAT terminals?

[m-mman]

As I see it the fuel gauge is the only key switched accessory. The ammeter is always on and the lights have their own switches....

 

Perhaps because of the design of the integral switch/coil, Dodge felt it was better to provide a separate switched terminal (which had to be located on the coil since the switch contacts are inaccessible) because if the fuel gauge drew power from the coil (rather than straight from the key) they thought it might reduce current to the coil thereby reducing the spark(?)

 

I don't think a fuel gauge is going to draw enough current to upset the coil but if you do put your coil on one terminal of the replacement switch and the gauge on the other it will be just as Dodge did it. 

 

[TerryB]

Agreed, you only want the fuel gage ON when the key is on.  

[frank29u]

I agree with m-mman and TerryB; fuel gauge should only be powered with key on, not all the time.  This was the middle terminal on key mounted coils I've seen and labeled GAGE or FUEL GAGE.

 

The BAT terminal is connected to Ammeter so it will show discharge when the key is ON.  The IGN is connected to Negative on modern coil and the Positive post on coil goes to distributor, as you have Positive Ground.

 

This is how I wired a back up coil in parallel on my '29 Plymouth.  A simple toggle switch in the "hot" wire, BAT/Negative, keeps both from being activated simultaneously.  I mounted the back-up on a cowl cross member to keep out of sight and without putting extra hole in the firewall.  Obviously the high voltage wire needs to be in the coil I want to use.  Use the key for key mounted coil or toggle for back-up, but not together.   I used 14 gauge wire on lamp circuits on this 4 banger,  10 on the rest; generator, horn/clum, starter switch to ammeter.  You can probably see the wire sizes Rhode Island used in their harness.

 

Hope this helps,

frank

Edited August 5, 2018 by frank29u
add Rhode Island sentence (see edit history)

[PFitz]

One other possibility is that two position, three terminal switch was meant for use where a separate starter button was used - like some boat engines are set up for. That would use the "str" terminal wired to the push button, then from the push button on to a starter relay.

 

A gas gauge does not use much current and won't cause much noticeable voltage drop that could affect coil voltage. Doesn't matter is it's connected at the switch or the hot side of the coil, the drain on the system is the same. Rhode Island Wire uses 14 gauge, as was originally used on many 6 volt systems. You can use 16 ga for 12 volt systems.

 

Paul

[Taylormade]

I think you hit the nail on the head, PFitz.  The starter button idea makes perfect sense - my 48 Plymouth started that way.

[Alfre]

I believe  the start terminal should be labeled accessory and the gas gauge would go there the rest would be correct.

Al  

[Willie Wurke]

I am going to be different from all the above!

Back in the good ol'(when we parked a lot!) days you could turn the key to the left and play the radio without burning the points.

 If you have this type ignition switch (3 position)the terminals will be BAT--Coil--Acc(gauges plus radio) 

 

Keep us posted  as ever ,Willie

[Taylormade]

Again, no three positions, just two - on or off.  I think the remote starter button theory is the correct one, thus three terminals on a two way switch.