TR2/3/3A Old school battery shut off switch.......

[karls59tr]

Found this in my parts bin. Thinking of installing it in my TR3. I assume it mounts near the battery but is on\off lever going to be difficult to reach under the dash? Has anyone ever used one of these?

 

[JHaydon]

Oof... old school indeed. My first thought is to put it in a museum and buy a new one, unless you can get inside and make sure the contacts are clean.

It doesn't necessarily have to be near the battery as long as it's near the battery CABLE -- i.e., the less you have to extend the battery cables, the better. A marginal electrical system will have a heck of a time if you add 5 to 10 feet of battery cable. If the switch is low-quality or has corroded or burned contacts, forget it. But since the battery is basically right on the other side of the dash, I don't think the extra cable would be a problem.

My TR3 has one of those green knob cutoffs (unscrew the knob to disconnect) that gets mounted directly on the battery post. It's more for long-term storage or anti-theft, not much use in an emergency, but it added nothing to the cable run.
Another of mine has a racing kill switch, unfortunately under the car in such a position that you have to shimmy your entire torso under to reach it... again, useless in an emergency.
One of Dad's cars had a racing kill switch mounted at the base of the seat (very close to the battery, which was under the seat). Perfect spot for emergencies, convenient for long-term storage, and hidden just enough that it probably would have been effective for anti-theft.
All three above had the switch located so the battery cable didn't have to be extended or looped around.

So the ideal location is close enough to reach in an emergency, hidden enough that a thief might not see it easily, and near where the battery cable is already. Under the dash seems like a pretty good spot, just not the most convenient.

But lucky you, there's a hole in the handle which is meant to take a lanyard or pull cable for remote operation. Mount the switch out of the way under the dash and add a simple pull cable, routed a little closer to where you can reach it (like taped to the back of the dash, maybe). Or maybe use a choke cable and mount the pull knob in plain sight. If a thief thinks he's got to pull it to get the car started, he will just be disconnecting the battery!

Oh, and -- don't EVER try to stop the car by turning off that switch (except in a real emergency). The contacts are (generally) designed for continuous duty, but the voltage spike that occurs when you break contact while current is flowing will burn the contacts. A typical kill switch can handle 100+ Amps and work for some thousand actuations, but using it to turn off the car will wreck it in about a dozen attempts.

 

[karls59tr]

Oof... old school indeed. My first thought is to put it in a museum and buy a new one, unless you can get inside and make sure the contacts are clean.

It doesn't necessarily have to be near the battery as long as it's near the battery CABLE -- i.e., the less you have to extend the battery cables, the better. A marginal electrical system will have a heck of a time if you add 5 to 10 feet of battery cable. If the switch is low-quality or has corroded or burned contacts, forget it. But since the battery is basically right on the other side of the dash, I don't think the extra cable would be a problem.

My TR3 has one of those green knob cutoffs (unscrew the knob to disconnect) that gets mounted directly on the battery post. It's more for long-term storage or anti-theft, not much use in an emergency, but it added nothing to the cable run.
Another of mine has a racing kill switch, unfortunately under the car in such a position that you have to shimmy your entire torso under to reach it... again, useless in an emergency.
One of Dad's cars had a racing kill switch mounted at the base of the seat (very close to the battery, which was under the seat). Perfect spot for emergencies, convenient for long-term storage, and hidden just enough that it probably would have been effective for anti-theft.
All three above had the switch located so the battery cable didn't have to be extended or looped around.

So the ideal location is close enough to reach in an emergency, hidden enough that a thief might not see it easily, and near where the battery cable is already. Under the dash seems like a pretty good spot, just not the most convenient.

But lucky you, there's a hole in the handle which is meant to take a lanyard or pull cable for remote operation. Mount the switch out of the way under the dash and add a simple pull cable, routed a little closer to where you can reach it (like taped to the back of the dash, maybe). Or maybe use a choke cable and mount the pull knob in plain sight. If a thief thinks he's got to pull it to get the car started, he will just be disconnecting the battery!

Oh, and -- don't EVER try to stop the car by turning off that switch (except in a real emergency). The contacts are (generally) designed for continuous duty, but the voltage spike that occurs when you break contact while current is flowing will burn the contacts. A typical kill switch can handle 100+ Amps and work for some thousand actuations, but using it to turn off the car will wreck it in about a dozen attempts.

I like the idea of a choke pull cable but on closer examination it appears that when the lever is in shut off mode the contact points are still fairly close to each other and a little bit of wiggling of the lever looks like it may make them regain contact? Might have to scrap the idea of using it? It would still work as a battery shut off if the contact lever was just pulled out of the assembly when needed but not very practical I suppose.

 

[JHaydon]

Maybe we should back up and figure out what your goal is for the switch.

If it's to disconnect the battery in case of an emergency ( ), then the pull cable should do it (as long as it's oriented so the weight of the handle and cable won't try to push it back towards "on"). Vibration shouldn't be an issue in that case except maybe in the few seconds that you might take to get the car stopped on the side of the road, or if the car is being trailered. And if it's 99% for emergencies, you could perhaps add a compression spring under the handle to encourage it to disconnect.

If it's mostly for anti-theft, vibration shouldn't be an issue but ease of access might suggest looking for a more convenient position. Since the cable trick would really only work to turn it off, getting ready to go again would be a hassle. The fact that the handle can be removed makes this switch even more effective for anti-theft. There are others on the market with removable keys, but the ones I've seen (the ones we sell) are all plastic and look very modern.

If it's just to isolate the battery for off-season storage, then I'd recommend the little green knob mounted on the battery post. No worries about burned contacts or misplacing the key. It's as close to foolproof as you can get. And it can work for anti-theft as well. How many crooks are going to have a T-key to get under the hood?