costas1 Posted November 27, 2012 Share Posted November 27, 2012 hi mates. i have a question and i need some help. i have the pressure switch for my water-methanol injection system. i tested the switch and it is always closed circuit(have volts on the meter). as soon as hits the pressure i have set to it the circuit opens(no volts)..the system also has a relay. is it possible that the relay's job is to reverse the function and when i have no volts on the meter it actually works on the car and make the pump work? i hope you understood what i am trying to say..thank you Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted November 28, 2012 Share Posted November 28, 2012 Yes, that's how it will have to work. The pressure switch contacts are normally closed. When the intake plenum pressure rises the switch contacts open and the relay which has a pair of contacts normally held open by the current through the pressure switch, is de-enegised and the contacts close. The pump then runs. It's VERY important to wire it so the pump cannot run with just the ignition on and flood the plenum with water. Wired normally if the relay fails with the ignition on the pump will run. You could introduce safety features, but it starts to get complicated then. Quote Link to comment Share on other sites More sharing options...
costas1 Posted November 28, 2012 Author Share Posted November 28, 2012 thank you sir.you have been very helpful Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted November 28, 2012 Share Posted November 28, 2012 I try, no worries Quote Link to comment Share on other sites More sharing options...
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