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-   -   Normally closed momentary switch. (

getnpsi 06-01-2008 02:39 AM

Normally closed momentary switch.
Where can these be sourced, other than door latches? I want to buy a "ricer" style shift knob and replace the normally open with a normally closed switch to cut fuel on demand (DFCO help) rather than try the vacuum idea. If the car doesn't stumble or code out from cutting fuel too early vs ecu's control ill add a vacuum switch to make it fully automatic. By having the button on the shifter I think it would become pretty second nature as I drive, but I'd hate to hit it on accident :eek:

cfg83 06-01-2008 04:10 AM

getnpsi -

You can get a "normally open" switch and attach it to a relay that you connect to be "normally closed". You attach the button so that when the button is closed, it forces the relay to go open. Not as elegant, but works like a charm and can take the worry out of switches not being able to "take the amps".

Otherwise, if you look on Marine supplies websites that specialize in 12 Volt electronics, you can (eventually) find these switches.

Good electronic switch site :

Switches - The Electronics Club

EDIT: Ha ha, found this 35MM diameter monster :

Momentary mushroom head emergency stop


getnpsi 06-02-2008 10:22 PM

pretty funny there, I might go for one of these ebay jobs and switch the switch. sually they unscrew from the bottom

ttoyoda 06-03-2008 01:40 PM

Plenty of switch choices here:
2 examples

getnpsi 06-03-2008 04:11 PM

i found some at radio shack but they are tiny. I wanted a lil bigger. Im going to install it today and let you know if the driveability suffers any. If it doesnt I'm getting the $20 vacuum one to make it not so mad scientist feeling.

cfg83 06-03-2008 05:00 PM

getnpsi -


Originally Posted by getnpsi (Post 30643)
pretty funny there, I might go for one of these ebay jobs and switch the switch. sually they unscrew from the bottom

I like this idea, but maybe with a different shape on the shift knob. If you look at this picture :

You can see that they are using a relay, but with only four pins. The 5-pin relays allow for normally closed momentary switching :

In the above, if you attach a "regular" momentary switch to connection 87, it will become a momentary open switch to create momentary fuel cutoff.


ttoyoda 06-03-2008 05:40 PM

If it doesnt I'm getting the $20 vacuum one to make it not so mad scientist feeling.

I always though the mad scientist feeling part is what makes it the most fun. ;)

getnpsi 06-04-2008 05:33 AM

Its on the car and running. Either I have leaky injectors or there are 2 grounds to the multipinned plug over there. I can hold the switch down and the car almost dies and just about when it does it stumbles back to life. I need to get the book out and see if there are 2 grounds in that part of the harness, or if its picking up a "semi ground," like in blinkers that alternate on some cars, where the ground wire becomes the parking light...if that makes sense. Anyway i mounted the switch on the console near the shifter and can hold it down below the 1500rpm and let go when I press in the clutch right before im stopped permitting the engine to stay alive. We will see if the addition of the switch combined with myself being so much more aware of decel benefits will help the mpg's. Anyway sucess, no check engines or anything else that i was scared of.

Oh wow I wasnt aware the item came with a relay? That would make everything very simple. Anyway it's working as-is so I can expand on it being totally confident.

COMP 06-07-2008 01:55 AM

was there 2 grounds ??

getnpsi 06-07-2008 01:09 PM

I've had a lazy few days and haven't done any more progress. I was using the button so often i snapped the thing off. Lucky for me they come in a 4-pack for $3.79. The other positive thing is when the switch fails on the top side the circuit is closed anyway, so I can continue to drive like nothing happened. This last full tank got me over 40mpg, but I can't say this helped any when I added wheel discs and drove on the freeway a lot more. The best thing I can see now is I can add the vacuum switch and not have a check engine light.

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