Battery Disconnect Switch?

[Jon37]

I used the familiar ''green knob'' battery disconnect switch for years on my 6-volt car, to disconnect the battery after I left the car in storage after each car show. Then, when I was encountering some electrical problems, someone told me it really wasn't that great for 6-volt cars (well actually he used more colorful language to describe the switch), and he suggested I simply remove the cable or ground strap each time I wanted to disconnect.

However, after several years of removing and replacing the ground strap I discovered the battery terminal and ground strap clamp had become quite severely scarred from constant installation, removal and cleaning. (In the last couple years I discovered that I had to clean my terminal and clamp each time, just to get a good connection). The battery was still good, and would turn over the engine, but there didn't seem much left for a spark.

I wondered what others are using to disconnect their batteries? Has anyone else had trouble with the ''green knob'' on a 6-volt car, or is it actually not that bad? Would the ''knife-type'' cutoff switch work any better? Are the panel-mounted turn-switches better? Does someone make a battery cable quick-connect ''plug'' of some sort? (I tried the forum search engine but didn't find a discussion devoted to this subject in the last five years.)

[Jan Arnett]

I ahve them of three cars of which two are 6 volts and I have only experienced one problem. I found that I was getting arching and could not figure out why. Turns out a dash light was shorted and every time I turned the knob off I have an arch. This saved my battery and it was not the fault of the switch.

[Guest Fr Mike]

I have been using green knob disconnect switches on my '31 Buick and '36 Plymouth, both 6 volt systems, for some time, with no trouble. Saves the battery when not being driven, is an additional safety measure, & is convenient when working on wiring. I do agree on the importance of keeping the battery terminals, cable ends, & switch clean, even more so on a 6 volt system than on a 12 volt one. A disconnect switch, especially a removeable key operated one, mounted where it can be reached by the driver, rather than on the battery, is a lot more convenient, provides a greater measure of safety, and allows the anti-theft factor to be nore easily activated.

[Ron Green]

I too have been using the green switch type for years with no problems however their contact surfaces seem to get semi corraded after several years. Now that you can buy these for $1 at the swap meets ( used to cost $6 a few years back) I just change them when they start looking or acting old. The Chinese must be working cheaper these days.

I also have the heavy type switch with a flip handle that works fine.

[KRK Sr.]

Jon37, Carquest sells a disconnect that I use for 6 volt, still has a knob, but you actually remove the ground cable and a large lead lug each time. I then place the cable far from the battery and know it would take an awful lot of bouncing in my trailer to get the current back together. Karl

[carbdoc]

Jon37 (and everybody),

Buy a knife-type cutoff switch made by Wirthco and you will throw rocks at the "green knob" switch for ever more. I used to use the green knob, but now I use the knife switches exclusively on all of my vehicles. While they are more expensive, I have yet to replace one.

Jeff

[mrpushbutton]

I'm a big fan of the Cole-Hersee (manufacturer) model 2484-16 battery disconnect switch. They are rated at 1000 amps intermittent, 175 amps continous. You can see a catalogue pdf at http://www.colehersee.com/pdf/master_cat/t_battery.PDF#search="cole%20hersee%202484-16"

[Fred Zwicker]

I was looking at the Cole-Hersee site and was wondering how they connect for a 6-volt system? Do you run a 6-volt type (read - very heavy) cable from the battery to the switch - then to the old cable? How far can you run such a cable? For a 6-volt system, looks like this would be a difficult installation, in view of such a heavy cable being required?

My 1939 LaSalle battery is under the front floor mat and requires pulling back the rug, unscrewing 4 bolts that hold down a metal cover and then removing this cover to get to the battery. I wouldn't want a shutoff switch in that location, as would probably not use it much. My present method is that I use a 6-volt Battery Tender, which keeps the battery fully charged all the time. The Battery Tender has a short wire from the battery connections (positive and negative) and this wire has a small plug on the end that lays in place along the edge of the carpet just below the driver's seat. The Battery Tender plugs into the wall and has a matching wire from the unit (charger) and I plug in this wire to the connection next to the seat, run the wire under the door and close the door. This wire is black in color and small, as all it does is supplies a trickle charge to the battery.

When I want to start the car, the wire is visible (so I don't forget it), so I simply unplug the connection and car is started quickly. When I put the car back in the garage, I plug in the wire again and it is ready for the next time. This works for me.

Fred

[ex98thdrill]

We've got the "green knob" on 8 of our cars (4 on a 6 volt, 4 on 12 volt cars) and we have had absolutely no trouble.

[mrpushbutton]

on most 1930s cars we mounted the switch to the front lip under the drivers seat, which is a very short run to the battery. You need a short heavy gauge cable (same gauge as the other battery cables) with eyelet style ends crimped on--a good auto electric shop can make those inexpensively. On some cars we put the switch in a hole in the firewall with the knob facing inside the car, near the starter. The only thing you don't want to do is add unecessary length of wire to the battery cables. on some cars we custom fab'ed a metal plate that the switch mounted in and fastened it somewhere under the hood, where we could take advantage of a pre-exsisting stud, hole or other feature we could use to avoid drilling holes or excessively modifying the car.

[carbdoc]

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">We've got the "green knob" on 8 of our cars (4 on a 6 volt, 4 on 12 volt cars) and we have had absolutely no trouble. </div></div>

Keep some Channel-Lock pliers and some dielectric grease handy -- the day your electrical system goes dead (usually while trying to start the car) you'll be glad you have them on hand. Unless they have inproved the design, the critical contact area between upper half of the terminal the bottom of the knob is just plain inadequate, and it is here that the bad connection occurs.

Jeff

[yirgaman]

I've been using these things for several years - maybe 10 and have had only one problem, one time, caused by the battery jiggling around and caused the knob to loosen enough that the starter wouldn't turn over. After I tightend down the battery never had any other problems. I suspect the newer flea market items are being made cheaper (less quality for less money).

Larry

[ex98thdrill]

Ok, without sounding rude, what is out there besides those that is better??

We've had these for years, and this is the first I've heard of any problems at all, and don't want any.

[DizzyDale]

Dear Pat,I use the one with the green knob,ONLY issue i have is the knob has partially melted.Must be hot under the hood of the 62.Dale

[R W Burgess]

Hey Dizz, I had a buddy hand me a green knob one day. It had melted right off his battery. The battery had shorted out overheating the disconnect. Luckily, this happened as soon as he shut the engine and down and smoke started to appear at one of our cruise-ins.

Oh, I still have that knob around here somewhere, if you need one. <img src="http://forums.aaca.org/images/graemlins/tongue.gif" alt="" />

Wayne

[carbdoc]

ex98th,

See my earliest post on this thread (9-26-06). The website address is www.wirthco.com. And yes, I know that they sell the "green knob" version, too, but the knife switch is the ONLY way to go unless you have a clearance problem -- or just enjoy the smell of melting plastic.

Seriously: a poor connection at the knob's contact "footprint" is typical of this design and can damage the battery (as mentioned above) or, worse, damage just about everything else in the electrical system. When powered accessories can't get enough voltage, they try to make up for it with amperage draw. Amps = heat. You get the picture . . .

Jeff

[Tom M]

Since my battery is pretty much accessible I just keep an extra wrench in glove box and disconnect it that way. Or is that not good for the battery?

[carbdoc]

Packin31,

That's probably OK; just be sure to have the bolts good and loose, and don't apply too much radial torque to the battery posts as you "twist" the terminals to get them to release or seat.

Jeff

[Guest Ken G]

I suppose this is a silly question, but why do you want a battery disconnect switch at all? I wouldn't have thought it was an effective way of preventing theft, since any thief wanting an old car would know to look for such a switch. If the wiring is in a dangerous state, resulting in a fire risk, a switch merely addresses the symptoms when the cure is new wiring. It must be comparatively rare that you need to be completely sure the battery is disconnected because you are doing something that might lead to a short-circuit, and on those occasions it is best to remove the cable completely.

Ken G, 1925 Rover 16/50 (San Francisco)

[Ron Green]

For vehicles that are parked for extended periods of time or even in between trickle charges a simple small clock draw will put a drain on the battery, thus starting the battery plate sulfating process and its demise.

I feel better with the power off my old vehicles as you never know when a mouse is going to chew and short things out and possibly start a fire.

Plus if showing your car with the hood or trunk open and you have a light it is easier to twist a knob the to keep wrenching a soft battery terminal bolt.

[Guest De Soto Frank]

Ken,

Probably most old cars "in good order" would never "need" a battery disconnect switch; but I personally know of two people in my area who lost entire collections/garages due to wiring fires in one of their antiques...

Either leaving the battery disconnected or employing a disconnect switch is cheap insurance in my book... the possibility of rodents chewing on an "organic" wiring harness is always a consideration...

(Or curious kiddos getting into the garage, stepping on the starter and taking old Betsy for short but costly ride into one end of the garage or another...)

I now disconnect the battery on any vehicle that I don't drive on a daily or at least weekly basis...

Any resolution on your oiling woes ?

[Guest Ken G]

Frank and others,

Thank you for the explanation, although I admit I am not totally convinced ... but then, touch wood, I have no rodent problems in my car. I have had rats in the garage/basement, but I am passing through daily so they are unlikely to settle in.

No, no news on the oil pump starvation. The car still goes and the problem remains. I have a recommendation for someone in San Francisco who might be able to remove the gearbox and clutch and reveal the oil passages that I suspect must be blocked, but I haven't made contact yet. I am in touch with someone in England who has another Rover 16/50 in more or less running order, and will visit him in January, so I may learn something then.

Ken G, 1925 Rover 16/50 (San Francisco)

[26pack]

I have a 26 Packard and the battery is in a battery box built into the fender. Using a standard disconnect switch is a pain because I might not have the clearance and I would have to take the top of the battery box off every time I wanted to connect or disconnect the battery. Does anyone know of a disconnect switch which might, for example, attach to the engine block or something? Thanks.

[carbdoc]

Ken,

I will jump back in here and give a big "Amen" to the comments made by Ron and Frank.

Also, I will observe that you probably don't own a Chrysler product; otherwise, the answer would be obvious! Mopars had notoriously under-engineered electrical systems and, when you own one and associate with other Chrysler owners, you quickly become familiar with the term "Mopar flambe'" (don't fuss at me, Frank, 'cause we both know it's true).

I wish I had had a Wirthco knife switch installed on my '61 Chrysler on July 4, 2001 when the wiring harness burned. As I waited my turn to join the town's Fourth of July Parade, the voltage regulator filled with "liquid sunshine" (yes, the regulator was that poorly-located) and shorted out. Poof: the wiring harness was on fire! I am fortunate that I don't have a permanment tattoo of a battery terminal scorched into the palm of my right hand from grabbing the terminal and twisting it loose before the harness could take the rest of the car with it.

This is not the only electrical system "horror story" I have accumulated over decades of Mopar ownership, but it may be the most dramatic. These multiple Mopar misadventures have made me battery shut-off "convert".

Jeff

[Guest Ken G]

Jeff,

Thanks for the further info. I potentially had something of the same problem in my Rover as designed and as I received it, because the wiring was in a sorry state and to my astonishment there was no fuse. Thus there was no protection between the battery and the switches (the horn was the one most likely to lead to a short-circuit). In rewiring the car I introduced a 20 amp fuse as the first thing the battery encounters (apart from the starter wiring which is not likely to fall apart), and I think it very unlikely that any dangerous problem would not blow that fuse. On the few occasions when I have needed to isolate the battery, I simply remove the fuse. However, I concede that a 6 volt system (mine is 12, and always was), requiring a much higher rating of fuse, might still be fire-prone.

Ken G, 1925 Rover 16/50 (San Francisco)

[carbdoc]

Ken,

Lack of a fuse is part of the reason my Chrysler's harness cooked; the voltage regulator was supposed to include an internal fuse which might have prevented the short, but it did not. Who opens up the case and checks for the presence of a fuse when one replaces a regulator? Well, I do . . . now. For good measure, I have now incorporated a waterproof in-line 5-amp fuse into my regulator field harness and hidden it beneath the regulator.

All of my Mopar electrical nightmares have involved 12-volt vehicles. If you under-engineer any electrical system sufficiently, there is no limit to its probability of dramatic failure. I firmly believe that Chrysler and Lucas had a foreign-exchange program in place to provide each other with underqualified engineers in case of an emergency.

In fact, I just now finished performing some electrical repairs on wifey's '71 Chrysler 300 which goes through ignition switches and signal flashers like Sherman went through Georgia . . . but we still wouldn't trade our Chryslers (or Rovers) for anything else, would we?

Jeff

[Joe Block]

I think Bill Hersh is selling a remote battery disconect swtich with a push button.

[Guest De Soto Frank]

Jeff,

I'm not going to "fuss at you"... <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" />

I'm sorry to hear that you had a near catastrophe with your Forward-Looker... <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" />

(See what comes from playing with modern, overly-complicated 12-volt cars? <img src="http://forums.aaca.org/images/graemlins/grin.gif" alt="" /> )

I think the booby-prize for "under-engineered" electrical systems has to go to GM... especially their full-sized trucks between '88 and present (?)...

Since recently purchasing an '89 Chevy 3/4 ton to be my everyday "go truck", I've been prowling the junkyards, looking for various goodies to make mine complete/nice again, and I've noticed quite of few GM trucks of this vintage that are crispy hulks due to (apparently) electrical fires that have been concentrated in the dash area. I have also had to repair fried tailight sockets ( damn 3057 bulbs!) and fried relay centers on a couple of these things... the wiring and connectors look very small for their duty, and while they may be "adequate" by the engineer's books, they certainly are not "over-engineered" or oversized, and won't tolerate much in the way of resistance or overloads...

To their credit, modern vehicles are thoroughly "fused", as opposed to my '41 De Soto, which has one factory fuse: SFE-30 amp on the headlight switch, plus an in-line fuse each on the aftermarket turn-signals and the optional heater.

I'm trying to remember where the regulator is mounted on my '60 Windsor... haven't had moisture problems there... (I guess I can't remember its location because it hasn't caused any problems yet...)

Now, the cowl, front floors, trunk, etc are another story, where "shipping water" goes... <img src="http://forums.aaca.org/images/graemlins/crazy.gif" alt="" />

But, the big battery master-disconnect is really the best insurance against a car "spontaneously" combusting if something, somehow, goes wrong... this would be especially true of a vehicle stored indoors, and with other vehicles, etc ; bad enough if one car burns, but if it takes the whole barn, or house, or worse... ?

[Guest Albert]

I will second that those 3157's are nothing but crap, I have seen more burnt out sockets that have melted from the heat of a poorly designed socket/bulb, what was wrong with the 1157, other than it being 50+ years old.. I still have the original sockets in the 54 Packard, none of them have melted.. i think a lod of car companys have had problems with car fires for one reasion or another ford escort had ignition switches that would catch, My 88 pontiac tempest the turn signal started to smoke when you pressed on the brake, when i took it apart i found the grease had become conductive form the metal that had worn off the contacts, and it was burning the plastic..

[Ron Green]

Quote; "I think the booby-prize for "under-engineered" electrical systems has to go to GM..."

Amphicar is right there with Lucas; critical large electrical rail connector behind the muffler in the rear compartment (impossible to get to), series of timing relays and a tube that go through a sequence that runs a blower for 2 minutes before you can start the engine (hopefully), electrical grounds for critical items through sheet metal screws, various wiring changes (and colors) for the same year, indoor rated connectors for a car that gets wet, electric fuel shut off that has a mind of its own, and ...............................................etc. <img src="http://forums.aaca.org/images/graemlins/frown.gif" alt="" />

Quote; "To their credit, modern vehicles are thoroughly "fused","

Just burnt one up a year ago (GM) as the rear lighter was held in (by my nephew) until a fire started and burned 3 wiring harnesses, computers, etc. Warning lemonade doesn't seem to retard a electrical fire so Im told. Very unusual the dealer stated. <img src="http://forums.aaca.org/images/graemlins/confused.gif" alt="" />

[Guest De Soto Frank]

So I'm somewhat justified in my patent dislike of new cars ? <img src="http://forums.aaca.org/images/graemlins/crazy.gif" alt="" />

[carbdoc]

Frank,

You are absolutely justified.

I had a 1988 GMC K-series (only new vehicle I ever owned). It had plenty of electrical gremlins: turn signal flasher failed at regular intervals, brake light switch would not stay adjusted, needlesssly complex (and failure-prone) "graphic" AC/heat controls. I did not know about their tendency to fry at the dash, but it does not surprise me. My "modern" ride is now an '88 Jeep Grand Wagoneer: just as electrically under-engineered as a Chrysler, but at least its areas of failure are more predicatble than that GMC.

Your '60 Windsor had a generator hence a different regulator which is probably not mounted up high on the left inner fender where as my alternator-equipped '61's was located -- right in the path of all of the rainwater pouring in between the hood and the fender.

Chrysler was aware that voltage regulators filling with water was a problem back in '61, too; I've seen the service bulletin. Their solution: glue a 6" length of weatherstrip above the regulator to deflect the water! How very professional.

Jeff

[mrpushbutton]

It's too bad that GM vehicles after the 1970's have gained this reputation for under-engineered electrical systems. They used to be the best--Delco systems in the 50's thru the 70's were unbeatable, especially when compared to Mopars.

KenG--I'm a big believer in disconnecting a car's battery during periods of non-use, especially here in the snow zone where we put our cars away for six months at a time. Besides clocks (more on that later) there can be leakage paths to ground that slowly drain a battery. If you are driving the car often enough you won't see this, because you are charging the system regularly. But with every passing day of storage you can be draining the battery to the point where it is stone dead unchargable scrap.

As for electric clocks: the winding coil on most car clocks is a simple mechanism, a clock spring (ergo the name) with a set of electrical points that close when the tension on the spring is low, engaging a solenoid that pulls the spring back to a high tension setting, rinse, lather ,repeat (and on and on).

There is a point when a car battery starts to lose its charge where the voltage drops well below 13.8V The clock solenoid will still try to do its job. Being an inductor, it will try to compensate for the lack of voltage with current, causing more amperes of current to be carried through the clock-points than they were meant to handle. The points will pit, and now you have a clock repair on your hands.

I worked for a large collection (140+ cars) for over 12 years. We installed a Cole-Hersee 2484-16 switch on all of the cars in the collection (regular drivers), and shut the batteries off from the cars the minute we put them in storage, or museum display. Never had a problem with those switches, and got in the routine of shutting them off when not using the cars.

[Ron Green]

Quote; "So I'm somewhat justified in my patent dislike of new cars ?"

Absolutely! Many of my friends say they tend to run forever however when the electrical systems start to fail send them to the bone yard. Of course my wife liked the car that burnt so much she had it fixed.

[Guest Ken G]

Well, I have enjoyed this, even if I am unconvinced. My Rover has zero drain when the lights are off, because lights and horn are the only electrical things there (magneto ignition, excellent spring-wound 8-day clock). Provided you are strong enough to start the engine with the handle (I am not!) the car will run without a battery. However, in connection with old cars, I have to add that I am amused at the extensive correspondence on another forum about hydraulics, both brake and clutch. Rods are so much more reliable!

Ken G, 1925 Rover 16/50 (San Francisco)

[Guest De Soto Frank]

That would be the beauty of the "K.I.S.S." theory: "Keep It Simple, Stupid"... <img src="http://forums.aaca.org/images/graemlins/wink.gif" alt="" />

Personally, I do not have disconnect switches on any of my vehicles, but those that tend to stay in hibernation for more than a week at a time, I disconnect the battery.

Same net result; makes "spontaneous combustion" a lot less likely.

<img src="http://forums.aaca.org/images/graemlins/cool.gif" alt="" />

[Guest Josh_Malks]

For me, the main purpose of a battery cut-off switch is to be able to quickly and easily disconnect the battery in the event of smoke or burning smells while out driving. To accomplish this the battery switch handle has to be easy to reach without opening the hood. The "green knob" switches are useless for this purpose.

For cars with an underseat battery the front seat toeboard is a perfect spot. Easy to reach, no additional cable length. For full voltage to your starter you should run a ground cable of the same gauge as the battery cable (00 welding cable is recommended) from the ground termonal of the battery to a bolt on the starter housing. This is the cable that should be interrupted by the battery switch. If the battery switch is in the hot cable, a short to ground can result in a fire. If it's in the ground cable, a short to ground is simply the equivalent of "switch on".

[mrpushbutton]

Welcome to the forum Josh. I have seen your name around the ACD club for years.

[Guest 70 Electra]

Have you ever seen a dead short in the alternator of a new car, that caused a fire in the garage and then spread to the house? It's rare, but it happens. And if it can happen in a new car, it sure seems even more likely to happen in a 50-yr old vehicle. That is why, as long as my "old" cars are parked in a garage attached to my house, I will ALWAYS disconnect the battery when they are not in use. That includes overnight!

I've used the green knob switches for many years without problem, until I tried one on my 60 Buick. Kept finding the dome lights on (and other electrical power), when the green knob was unscrewed a couple turns! I came to find that due to the height of the knob, when unscrewed, the hood was pushing down and SOMETIMES allowing the shut-off switch to make contact between its two halves. Probably wouldn't have passed enough current to start the car or do harm in case of a short. However, I didn't like the situation and have removed it.

I have the Wirthco blade switch on one of my other cars, and find it is a very nice product. I agree it is far better than the green knob type. Plus, (at least for now) it is still US made. I haven't yet found something I like that fits on the 60 Buick.

[carbdoc]

Greg,

Have you tried one of Wirthco's low-profile knife switches in that '60 Buick application? Its blade swings in an horizontal instead of vertical arc. Go to www.wirthco.com and you can see a picture of it online. It may or may not work; I couldn't get it (or any other design) to work on an '87 Jeep due to clearance, but I've found one to work on all of my other vehicles just as you did.

Good luck.

Jeff