Momentarily Grounding a Switch

Discussion in 'The Projects Forum' started by wrangler03, Feb 13, 2009.

  1. wrangler03

    Thread Starter New Member

    Feb 13, 2009
    Hello all, this is my first time posting and I have a question.

    I am planning on working on a project that I have been contemplating for a while. Almost everyone who has a car knows that car has an "Overdrive-off" button somewhere on the dashboard or gear shifter. Whenever I get into my vehicle and go for a drive around town, I need to press this button to prevent my transmission from shifting to fourth gear and therefore it shifts First-->Second-->Third only.

    In short, I am looking at creating someway to automatically click this switch off for me when I turn my ignition on instead of me having to switch it off every time I restart. I have a service manual for this vehicle and I was looking at the wire diagram for this circuit. The switch is wired into a control module for the transmission and it shuts the overdrive off when you press the switch by grounding the circuit out, I would guess momentarily. There is an indicator light on the switch that lets you know when the overdrive has been switched off, and additionally, you press the switch again to resume overdrive function for highway driving.

    My question to the forum is would there be anyway, through wiring a relay of some sort, to ground this switch out automatically when I turn the ignition on? I figure I would need to tap into a 12v source from somewhere that is hot when the ignition is turned on, which is not too hard to find.

    My apologies for the long-winded posting, I'm just trying to see if this is possible. Thank you in advance.

  2. Bernard

    AAC Fanatic!

    Aug 7, 2008
    Here is my take: Capacitor value depends or relay coil resistance and desired time of switch closure, something around 200 μ F.