Hi, I have an early 1923 Canadian Tourer.... I recently purchased the Master disconnect switch and bracket from Langs to kill all power in the car. I am needing advice and pics of where people have found the best place to put the switch and joined the bracket to?

Any one able to take a pic of where they have put the bracket and switch?

Cheers Simon

Best to put it back in the box. If you start the car with the battery disconnected it will fry your generator. Or if the switch failed internally, or one of the terminals were to come loose while driving, same thing, the generator gets destroyed. There is no reason you should need one of these switches. It simply introduces a new place for failure to occur.

Simon..I put mine under the front seat and attach
it to seat riser.

I have to agree with Royce on this one. These turn into the biggest source of trouble that I encounter when trying to help people with electrical problems. Assuming there is a need for this switch in the first place (which I doubt), there simply is NO WAY to make an effective RELIABLE switch that can handle the amount of current needed unless that switch has gold contacts that are massive. Last time I looked - none of the switches offered had precious metal contacts. Model T's were NOT famous for bursting into flames during their era. I believe in prudence as well as the next person and wiring shorts are certainly a reality but a fuse in the light wiring makes way more sense than attempting to install a huge switch in the main supply. Most often these switches are installed based upon "fear" selling or inability of owners to accurately diagnose electrical problems that are plaguing the car. The only positive thing they do is give a false sense of security to aid in sleeping. I say false because they are solving a non-existent or incorrectly diagnosed problem by inserting a real problem. If you are going to store your T for a long period of time - take the battery out or lift off one battery cable. Then clean it good when you put it back on. Just my .02 - your mileage may vary.

Ditto Royce & John

"take the battery out or lift off one battery cable..."

ALWAYS remove the ground cable first. There is no voltage there for your wrench to get between the post and ground.

Then wrap the post with tape to protect it from grounding out if you're going to remove the (no longer) hot cable. With the ground post isolated no current can flow if your wrench gets between the "hot" post and ground.

This applies to all batteries, and should be made habit.

If you insist on the switch, put it in the ground side. I have some I've removed. Guess I should foist them off via Tbay...

"BEWARE the LOWLY CAR BATTERY"
http://www.graybeardaviation.com/safety/batt4329.html

rdr

I have had a master cut-off switch in my '24 for 5 years with no trouble. For me it is a security measure for both electrical and theft measures. Mine is in the cable from the battery to the starter right near the battery. I check the terminal tightness each spring and find everything solid. It just seems like a reasonable thing to be able to disconnect the electrical power. Henry didn't see the need but I don't think he would object. $0.02

I had one on one of my cars for a few years and one time when I thought the battery had gone dead, I found it was the switch had corroded. Fortunately I didn't ruin the generator. If you have good wiring you shouldn't need the switch, and as stated by others above If you want to store the car, just lift the battery cables off the terminals. actually only the ground cable needs to be lifted.
Norm

Who's going to steal a Model T by driving it away? Anybody old enough to know how is too old to steal.

Now if you want to kill that stupid starter switch so you don't accidentally engage it while working on the car, or if kids play in the car, then a kill switch has some utility.

I spent my money on a starter solenoid and ran the energizing voltage to it through the ignition switch. With ignition off, you don't engage the starter. You can then safely keep the factory starter switch, or hide a button somewhere on a pre-'19 car. Mine is on the bottom left front corner of the seat.

It took me only one time of laying the floorboards of the speedster on the starter switch to work on the tranny to get the message. I leaned on the loose floorboards and engaged the starter. Luckily, my fingers weren't deep in the tranny.

rdr

I have one on both of my cars & if you use the switch to break the ground it will not corrode or go bad from current running through it. try it it works ...

There are at least 8 relatively recent cases of a garage burning with a Model T inside. The Model T was never blamed, but in each case, I suspect it was the blame and the fire started in the ignition switch or ammeter.

The reason I suspect that is because I know of four other cases where a fire did start that way.

The main reason for this problem is that the wire from the battery to the generator cutout is always hot and power is not removed with the ignition switch turned OFF.

A Master Switch is an excellent safety device for this reason, but it should never be turned off with the engine running, as the generator will try to use all the current generated and self distruct almost immediately.

James,
A master switch is not a safety device, a fuse is a safety device. The examples you gave of cars burning up would not have been prevented with a master switch unless the switch is always off including while the car is being driven, however, a 25A fuse on the small battery wire comming off the starter switch would have prevented the fire when parked and while driving.

My safety tip is for everyone to add a 25A fuse as close to the batery as possible and disconnect the battery when the car is in long term storage or whenever maintenance is being performed on the engine, transmission, or electrical system.

I use one of the small master switches that connects directly to the battery terminal. I have the habit of turning it off whenever I am not using the car for any period of time. It eliminates the problem of the kids getting into the car and stepping on the starter switch and/or playing with the ignition and leaving it on. I also am aware that there could be problems with them and if I suspect a battery issue the first thing I do is remove the master switch to eliminate that as the source of the problem.

I have heard of a Model T bursting into flames. Apparently the car was loaded into a enclosed trailer. Somehow the key got left in the ON position. The car was trailered home and during the ride the bouncing was enough to nudge the timer slightly causing one of the coils to buzz. The next day the owner came out and noticed that there was no paint on the outside of his enclosed trailer and it was very hot! The fire department was called, the trailer opened and the fire extinguished. Apparently the coil buzzed for so long it got hot enough to set the firewall on fire! A master disconnect would have prevented that.

Dave S.

If you don't remember to turn off the ignition, will you always remember to disengage the master switch? I have an idiot light connected to an oil splasher that also reminds me of ignition. Rather than a fuse, I have hidden circuit breakers, which are more reliable.

I heard of one T that burned up in a garage. The owner was later charged with arson.

rdr

A 30A fuse protects my electrical system beyond the starter switch, but the main reason I have an isolator is in case the starter switch insulation breaks down. I have one of the green knob type that attaches directly to the negative battery terminal. It never gets warm when using the electric starter so therefore voltage drop across it is irrelevant.
One would have to be in an unusual state of mind to lift the wooden cover out of the back floor and unscrew the green knob with the engine running instead of turning off the key switch first.
At displays where the car is unattended, being able to turn it all off prevents an endless queue of horn button pushers. For cars with no doors, the car won't jolt forward out of its parking space when someone attempts to find out what the button on the floor does, which I have seen happen.

You want opinions? You've come to the right place! lol

I put mine behind my left heel sticking out from the front seat. It only cuts off the negative / ground.

If the battery disconnect switch actually worked reliably all the time every time - it probably would NOT have the terrible reputation that they have. No one who is opposed to them (and that certainly includes me) would be so opposed to them but unfortunately they DO cause problems because they do not have precious metal contacts which prevent oxidation on the contact surfaces. If they did you would need a lot of bucks to buy one. Most switches for various things can tolerate a small amount of contact resistance and that is taken into consideration when those type of switches are rated - UH - what is the guaranteed rating in amps on the battery disconnect switch that you bought? Have they been tested by ANY independent laboratory anywhere? Since your main reasons stated were about safety - does it make sense to install something that does NOT have a maximum rating clearly marked on it? The problems they cause are compounded by the somewhat unique needs of the Model T electrical system. If your switch is defective it will often be intermittent first and it will go OPEN while you are driving down the road running on Magneto so you will have NO CLUE that your generator is being toasted until well after the fact. If you honestly think you will see it all happen in time to prevent this then you will just have to learn the hard way and some can only learn that way. I am sure I have not changed anybody's mind but I figure each of us really SHOULD share our experiences so that at least a new hobbyist can have the benefit of that and then make up their own mind. I have presented my case - you are the jury.

The 25 Amp fuse is not a complete safety device either, if it blows you burn up the generator anyway.

With no power applied to the Model T, when the switch is OFF, the garage will not burn. That is what I consider a safe mode of car storage.

James:

Your logic is not correct. The fuse will blow due to an OVERLOAD exceeding 25 amps. The switch goes OPEN without any load at all. If a 25 amp fuse needs to blow because there is more than 25 amps flowing through it - you could not possibly be better off without it in the circuit since saving your generator is the least of your problems at that instant since the wiring is getting ready to melt. The fuse limits the amount of current that can flow in the smaller wiring of the T. The switch does NOT limit this current at all when closed. If the fuse arbitrarily went open as does the switch then you would have a case against it but it is installed and not removed and inserted in the manner of regular switching that the disconnect switch sees. The fuse also has a RATING which can be depended upon since it IS a safety item.

John

I understand the fuse for a T, in fact, I will be adding those to mine.

As for a disconnect, wouldn't a knife type be the most safe switch if you don't want to fuse the yellow lead? Any disconnect on the battery would be best I would think.

The remote located rotary disconnects can go bad like any switch, but the 'knife blade' at the battery source seems like it would be unable to self destruct and cause electrical feed.

Dan:

There is NOTHING undesirable about having a battery disconnect. That is NOT the issue. The problem is trying to place such a disconnect in the main high current leg (either one for that matter) and have it work every time without any issue. While it certainly makes more sense to put it in the ground leg as others have stated - the problem is that such a switch needs to have VERY VERY low contact resistance if it is to carry STARTER current. When brand new some of them aren't too bad but they quickly get a small amount of tarnish (if they are brass and most of them are) or corrosion on the surfaces and the resistance goes up quickly. If we assume the starter current to be somewhere above 100 AMPS then we need the voltage drop to be very small in order to keep the thing from getting hot. Even a resistance as low as .003 ohms would produce 30 watts of heat since 100x.003=.3 Volts of loss and .3x100=30 watts of power. Now .003 ohms is a VERY small amount of resistance and chosen out of thin air for my example but if the thing gets just a bit tarnished the resistance can double and now you have 60 watts of heat produced. The numbers go up quickly and guess what happens to the resistance of copper or brass metal when it gets hot? YEP - it goes up. In your picture you have not one but 3 connections and ONE of them is very prone to getting weaker. What does the manufacturer rate the amps on this switch for? My bet is that there isn't any official rating. Brass and copper tarnish and dissimilar metals corrode so unless that bolt is stainless steel - it is gonna be a source of corrosion by itself. If the bolt is NOT stainless then what does that tell you about the engineering skills of the company that made this thing? They only need it to work one season is what I am thinking. Sorry but I just think one is better off spending money on new wiring harness and rebuilt ignition switch and checking out the whole electrical system completely. The whole job can be done in very little time. I have worked with electrical stuff since I got my ham license in 1959 and I sure don't want to take any chances on losing my T or house but I rely on just good thorough practice of good service and one good fuse that is in the leg most often subjected to trouble. I don't like the idea of driving my T down the road and hitting a bump and having my battery then suddenly becoming disconnected on me because of some import switch that somebody told me to buy and put on my car to make it "safe". If these really were necessary - wouldn't a modern car have an automatic battery disconnect relay that opened up when you shut your car down for the day? If it makes you sleep better - put it on - Ron Patterson can always rebuild your generator if you burn it out.

Dan,

The switch you have pictured has another serious safety issue. It is located right next to the battery. Lead acid batteries give off explosive fumes. One does not need a source of ignition ajacent to a source of fuel in the presence of air.

Caterpillar and other heavy equipment manufacturers have been using good master disconnect switches for years. They stand up to a lot of pounding with minimal failures.
There is even a UL spec for them.
They range about $40-$60, (cheap insurance)

Master Disconnect Switches designed for 12 VDC vehicles (Truck, Automotive, Marine, RV) to disconnect all circuitry to reduce possibility of theft and accidental electrical fires. Available in keyed or lever versions, with or without indexing pins, and various sizes of terminal studs.

Lever Operated- 6-36 Volt- 180 Amps continuous capacity 1000 amps in Rush S.P.S.T. (Off-On) Two stud terminals for battery circuit only. Does not disconnect alternator or generator field circuit. On vehicles equipped with alternators, engineer must be shut off to avoid potential damage to alternator diodes.
Incorporates heavy duty contacts.
One piece die-cast housing sealed with O-rings at base and mounting stem to keep out dust and moisture.
Large die-cast, lever for ease of operation.
Two 3/8" copper alloy stud terminals with hex nuts and lock washers.
Overall length 4 3/8". Diameter 2 5/8" approx.
Conforms to requirements of U.L. #558
Mounting stem 3/4" diameter, l/2" long, with two hexnuts and lock washer. (Note: Mounting nuts not to exceed 12 ft. Ibs. torque).
Designed for protection against battery drain, electrical fires, tampering and theft.
Fits panels up to l/4" thick.

Cheap insurance is a 25A fuse. An expensive way of disconnecting the battery when not in use is a master disconnect switch. The cheap way to disconnect the battery is a 1/2" open end wrench.

Well I would like to add just a litle food for thought. As a retired Nascar Crew Chief, I have had alot of experience with battery cut off switches. Whether you realize it or not, every Nascar race car has a rotorary battery cut off switch that not only has to be accessible for the driver, but also so the safety crew has to be able to reach in through the window to shut it down. I am not just talking about the big boys on TV, but every local track has this rule too.

Now I do not have one on my model T, probably because I figure if it burns up, well I will get to shopping for another one. Now to get back to my point, it is like anything else, there are good ones and bad ones. When I left the shop we had 9 race cars that all had switches that were atleast five years old and we never had a failure. When we would build a new chassis, we would transfer them from the old car to the new one because I guess they never caused us an issue. To me racing tests everthing to the extreme. We would wire them into the ground coming from the battery and used optima batteries. Now we were drawing alot more amps than a model T and they also survived the winter storage here in Wisconsin.

We would puchase ours at lefthanderchassis.com, I believe they were longacre brand and were 175 amp continuous and 1000 amp peak. If memory serves me right, thye were about 30 bucks. Moroso makes a nice one too.

Well just sharing a little experience, if you want to put one on your T, then go for it, if not, then that's OK too!

John,

While I agree with your dislike of battery disconnects available today, I'm wondering how, given the points you made above, the starter buttons, (the good ones, not the crappy repros.), are able to work so dependably without precious metal contacts? Especially since the starter button contacts not only must carry that same load, but must also "make" and "break" the connection while under load.

Ok, nobody else has said it, and John is sticking to the forum principle of avoiding self-promotion. You need two components to protect your electrical system: The 25A fuse that has been mentioned several times, and John's voltage regulator, which has a protection circuit for the generator should the fuse blow with the engine running. My master disconnect is the one Jeff recommended - a 1/2" open end wrench.

Jerry:

The starter buttons use a wiping action but they also get hot inside due to their contact resistance which accounts for a pretty good chunk of the total voltage drop when starting. The switch also has a ton of force applied (your foot) to help. If you had that much force applied with the blade switch you probably couldn't get it to close or open. The 6V starter switches (even the Ford design) are slightly marginal and likely one of the good reasons that modern cars changed to 12V so the current was cut in half. They also make way more intelligent use of the power of smaller motor as starter motors. Ever notice how much smaller the modern starter motor cables are? Even when compared to somewhat earlier modern cars with 12V. Precious metal makes for a good contact but there are also other contact materials that will do OK so long as the number of operations is less. In a product I designed one time we in fact used Rhodium as a track material plated onto copper traces on a Printed Wiring Board. The track had a spring that rubbed back and forth across the track with each line of the small printer that it operated. Tons and tons of operations and it seemed to never wear out. I always wondered how that might work as a switch contact material. The one switch that was presented by Ken Todd above looks way way more quality than anything I have seen offered to the T hobby or at least way better than most T guys BUY. Now that switch has ratings and UL code and all. If you MUST do a switch - at least that one appears to have a better chance if properly mounted and its "operational life" rating (number of switch events allowed) is not exceeded. A unique problem with some low voltage switchs is that they don't get operated often enough to keep their contacts clean. Had a guy call me once who was looking for new relays to operate his power window motors on an early 50's Chrysler that had 6V system. He said all the relays were bad and had bad contacts. I convinced him to remove the relays and operate them off 6V but to put a light bulb and 120v wired in temporarily in series with the contacts while the window motors were disconnected since he couldn't get at the contacts to simply clean them. It worked. A couple of operations and the extra voltage arced over and burned off the tarnish. All the windows returned to full operation but I also warned him to run the windows up and down at least once a month to keep the contacts clear of oxidation or whatever was on them. Don't know but I would guess the contacts there were silver. I never saw the actual setup since it was just a telephone call from John Q. Public.