burglar anti-theft switch HELP

[tedtaylor]

HELP Looking for quick answer (also posted to Electric section)
here's my '73 Sprint switch i just pulled to examine and do the surgery on.
So someone experienced, please confirm that i am jumping the two white wires?
if the switch (without taking it apart) follows that in the up position, the upper 3 wires (white, white, purple) are connected for allowing car to start and run....
AND if switch in down position, the middle white, purple and black are connected keeping car from starting.
please chime in authoritatively if you know for certain so i can bypass this "suspect" switch which may be contributing to my intermittent engine running.

[Craven]

Clearly not the response you demand but, the switch has two sets of contacts left side and right side there is no connection between the sides in any position.
In the run position the two white wires are connected together powering the coil, the purple and black are not connected together.
In the anti-theft position the two white wires are not connected together no power to the coil, the purple and black are connected together.
Horn is operated when the purple wire is grounded normally through the horn push when the ignition is switched on. Purple wire on switch is connected in parallel as a second purple horn wire, in anti-theft, this wire is connected to the black a ground wire thus taking the place of the horn push, when a thief switches on or hot wires the car, the horn is provided with both + and – and the horn sounds.
FWIW

[pharriso]

So someone experienced, please confirm that i am jumping the two white wires?

Ted, confirming that you want to short the 2 white wires if you are bypassing the switch.

[tedtaylor]

Perfect!
this answers my question and THANKs for pointing out that the switch does not cross over side to side, so your explanation makes perfect sense.
Now I feel very comfortable jumping the white wires together.

[pharriso]

p.s. You can get a replacement switch from Radio Shack (if they still exist ?!), their part # 275-0403

edit: looks like they are still around - https://www.radioshack.com/products/pk2-slide-dpdt-sw

[disquek]

This was an almost exact replacement for mine (which was also causing intermittent issues).

https://www.amazon.com/gp/product/B00BY ... UTF8&psc=1

-Kyle

[miked]

There is room for a proper toggle switch that is much more robust. Just make the hole round and use a nice washer. I have experienced the new ones dropping apart and acting up before they do. Not a very positive action. High resistance in the coil circuit. Just what you need. Also that silly long route around the near side of the engine bay and across the nose and back to the coil in a thin white wire. I run in a better csa wire to the offside using the shorter direct route.
All what I have said is useless if you are a purist.

[Andy8421]

In a previous life I used to specify switches for a living and to echo Mike's point, these switches are rubbish (both the original and the modern replacements). In fact they are only second in the dreadfulness ranking to the repurposed courtesy light door switches that Lotus laughably call 'microswitches' on the headlights.

If reliability is your aim, then Mike's advice is well taken - get rid of the switch and the loop of wire entirely, or if you think that there is a security benefit to having the switch then a decent, sealed contact, 'over centre' positive action toggle is a good bet.

As for security, I plan to use 123ignition's bluetooth distributor which (I believe) you can immobilise with your phone when you park the car. Unless the bad guy has a spare distributor, the car isn't going anywhere (unless he has a flatbed of course).

Andy.

[disquek]

My old one only lasted 50 years. So ... yeah ... unreliable ... In 2071 I will buy another one. lol

[miked]

My old one only lasted 50 years. So ... yeah ... unreliable ... In 2071 I will buy another one. lol

So you must have worked on and looked after lots of peoples Elans who have never had a breakdown or repeatedly poor starting due to this switch. My appologies for my poor information.

[Andy8421]

My old one only lasted 50 years. So ... yeah ... unreliable ... In 2071 I will buy another one. lol

Component lifetime is a statistical measure with a probability distribution. At one end of the curve there are switches that last 50 years, at the other, switches that pack up after a month. You were lucky first time around, perhaps the next one you get is a 'one monther'.

When lifetime is quoted, it is usually to some confidence interval - something along the lines of '95% of the switches will still be working after 2 years' The shape and mean of the distribution allows you to calculate the chance that the switch you buy will still be working after 50 years. With this design of switch luck really has been on your side.

Some of the problems with the switch have been mentioned:

Contacts aren't sealed - crap and corrosion can get between the contacts
There is no positive location - you can move the switch to some indeterminate position which may lead to contact arcing and failure.
Contact pressures are low, leading to high resistance, overheating and failure

I guess the main benefit from Chapman's perspective is that it was cheap. It is definitely up there on the list of things that are going to leave you by the side of the road. I removed mine soon after I purchased the car.

[disquek]

I’ve owned a couple of Elans. And had friends with them that I’ve looked after. I’m no full time Elan mechanic.

I’ve seen the threads here about these switches. And I can agree that there are better designs. Mine had been nicely relocated by a PO and a larger toggle switch wouldn’t fit, so I chose to replace like for like. I did consider replacing it with a dab of solder and some heat shrink. But I felt it was clever.

None the less the OPs and mine both failed at 50 years. I find it a bit over the top to call that unreliable. Ideal? No. Maybe a opportunity for improvement.

It’s funny to see the threads about replacing things like the awful vacuum pods being called heresy.

[Quart Meg Miles]

It’s funny to see the threads about replacing things like the awful vacuum pods being called heresy.

Yes, when it's so easy to fit an electric handbrake and repurpose the pull handle to raise/lower the lamps.

[nomad]

In the US, just having a standard transmission has become a theft deterrent. No one knows how to drive one anymore!

Kurt