Somebody

Yesterday I was really cleaning out the inside of the car and found a toggle switch under the parking brake. The only time it's pressed down is when the parking brake is down. I have no clue really what it's for except for mine is an 86 with the key hole for the security alarm. I figured that might have had something to tie into it since from what I've heard. Most of the time those alarms systems caused problems and were "unplugged". I can get some pictures sometime if you all need. I was just wondering what it was since I've never seen one there before on another 944.

Manning

It is a plunger switch, not a toggle switch and it causes the dashboard parking brake warning light to turn on and off. Lower the parking brake handle down against it and the light on the dash should go out. Raise the handle and the light should come on.

Zero10

Yep, it's a normally closed momentary switch. Open while the parking brake is down.

Peckster

It's a spring loaded switch that's open when it's depressed. A toggle switch has a longish stalk that flops back and forth for open or closed.

End of switch terminology lesson.

Chris_924s

or SPNO (Single pole, normally open) switch.

Now.. On to NAND gates...

Peckster

Nomally open? I'd say normally closed, because that's the way it is when there's no pressure on it. But there's no way it's a momentary switch. That's push for open, push again for closed, right?

Whatever.

Zero10

^^^
My thoughts exactly.

Hehe, NAND gates... don't see much of an application here though.

Techno Duck

If you parking brake warning light does not work, its probably because the small wire lead slipped off the spade connector. Happened on mine...i was dreading removing the gauge cluster again (i had removed it too put in FlamingEye's LED's) just too replace a tiny bulb. Turns out it just needed to be plugged back in.

How it slipped off in the first place i have no idea...its a pretty snug connection.

Manning

No, momentary is push for open (or closed) and release for the opposite.

Zero10

Yep, the other one is push on, push off, at least that's what I call them.

Danno

The mechanical state of the switch has nothing to do with the electronic contacts. Imagine installing the wall switch for lights upside-down or right-side up. In one case, pushing down turns on the lights, in the other pulling up turns on the lights.

Zero10

Well, sort of. Given the positioning of the switch, the only way for it to work properly would be if it was a normally closed momentary switch.

I would also argue that the mechanical state of the switch is not related to the electrical contacts, given that the mechanical state of the switch varies with time. The argument is simply that when the brake is in the down position, it opens the switch, when the brake is up, the switch is closed. In this case, the switch is a normally closed momentary. For it to be a normally open momentary, the brake handle would have to push the switch closed, thereby potentially limiting the travel of the hand brake, since the level would have to push against the switch. This setup is also more unreliable.

Unless, your argument is that they use some kind of NOT gate on the switch, which would allow the use of a normally open switch, which would cause the light to come on in the event that the switch became unplugged.

VaSteve

This is really as simple as a plunger switch? I was removing my carpet and reinstalling it without the 30lbs of padding and now the light won't go off when the handle is down. I must have boogered something up. I was really careful to ensure the wire was connected. I don't have time get to mess with it....so it's a simple switch huh? Does anyone recall if you can get the warning light to turn off without running the engine? I'd like to troubleshoot without the motor on if possible.

J Silverman

I would think that the light would turn on with the key in the on position.