Attention: TDR Forum Junkies Hmm, cute. Glad this one got bumped, as I was just thinking of tackling this problem, and this looks to be a bit more elegant than the solution I was considering (grabbing a pulse from the starter circuit to latch the switch).
If I read this correctly, when you turn on the key, the cigar lighter circuit goes hot and energizes the relay coil, which will connect pins 87 (which has nothing hooked to it, here) and 30. When you hit the starter, the cigar lighter is de-powered along with the rest of the accessory stuff, the relay coil de-energizes, and pins 87A and 30 connect -- having the same effect as pushing the EB switch -- with the resistor keeping you from getting too much current on what could be a sensitive ECM discrete input. Release the starter and it's like letting go of the button again.
Clever. About the only thing I could think to add would be a diode across the relay coil pins to take care of the collapse current when the power's shut off; but that's probably overkill, as it's connected to the cigar lighter, and I imagine that's used to seeing some pretty chunky power loads from all the stuff that gets plugged into it.
This should work for any other momentary-contact switch on the truck, just by doing the same with thing another relay (don't try switching a lot of things off the same relay) and wiring pins 87A and 30 across it instead of the EB switch.
--Ty
If I read this correctly, when you turn on the key, the cigar lighter circuit goes hot and energizes the relay coil, which will connect pins 87 (which has nothing hooked to it, here) and 30. When you hit the starter, the cigar lighter is de-powered along with the rest of the accessory stuff, the relay coil de-energizes, and pins 87A and 30 connect -- having the same effect as pushing the EB switch -- with the resistor keeping you from getting too much current on what could be a sensitive ECM discrete input. Release the starter and it's like letting go of the button again.
Clever. About the only thing I could think to add would be a diode across the relay coil pins to take care of the collapse current when the power's shut off; but that's probably overkill, as it's connected to the cigar lighter, and I imagine that's used to seeing some pretty chunky power loads from all the stuff that gets plugged into it.
This should work for any other momentary-contact switch on the truck, just by doing the same with thing another relay (don't try switching a lot of things off the same relay) and wiring pins 87A and 30 across it instead of the EB switch.
--Ty
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