ZeroMick Posted May 11, 2018 Share Posted May 11, 2018 A bit of a two part question here... with photos! I've recently changed the manifold/carb setup on my monte (originally 2barrel) to a 4 barrel setup and have done away with basically everything manifold and up. This has left a wiring harness from what I think is the the idle solenoid free. My question/s what did the idle solenoid do and two, what power is running through these wires? (please say 12v when the key is on) I'm hoping I can use them as a relay power for electric fans. thanks in advance forum legends. Quote Link to comment Share on other sites More sharing options...
cny first gen 71 Posted May 11, 2018 Share Posted May 11, 2018 Yes it is supposed to be 12 volt with key on I'd check it to be sure. I used mine for power to my petronix igniter. I left the selonide off mine also when I went from 2 to 4 bbl. Quote Link to comment Share on other sites More sharing options...
Rob Peters Posted May 11, 2018 Share Posted May 11, 2018 One of the purposes of the solenoid is to prevent engine run-on (dieseleing) after the key is shut off. The idle is set with this solenoid is energized and the solenoid plunger extended. When the key is turned on and the accelerator pedal is depressed the plunger extends to hold the idle at the set position. When the key is turned off the plunger deenergizes and the solenoid plunger retracts which drops the idle position below the set position which in effect starves the engine of gas and helps prevent the dieseling or engine run-on. That said, yes as long as the key is turned on there is 12vdc at that connector. Keep in mind, some of these fans are thermostatically controlled and don't come on until the temperature reaches a set point and don't shut off until the temperature drops below a set point. You may have noticed the fans on some cars continuing to run after the key is shut off. Since power would be cut when the key is shut off the above type of fan setup may not work. rob Quote Link to comment Share on other sites More sharing options...
stangeba Posted May 11, 2018 Share Posted May 11, 2018 I removed it from my 71 stock 350 4BBL way back in 71. On my Non A/C 71 it was energized when in high gear to prevent the throttle from closing all the way to idle speed. When the throttle is closed and the vehicle is "coasting" a richer mixture is sucked into the engine, causing higher emissions. To adjust this speed, the solenoid would also energize when in reverse so the speed could be adjusted. Many people didn't like this because the car felt like it was not slowing down when you lifted your foot off the gas. In most cases that was because it was adjusted improperly and too high. On my 71 it also prevented vacuum from entering the distributor vacuum advance till the engine was in high gear again for emission reasons. 72 was different, and I don't know about 70 and or if A/C vs. NON A/C was different. I ran my vacuum hose from the "ported" outlet direct to my dist vacuum advance, per advise of my brother in-law who was a power train engineer at Chevrolet at that time and knew these devises very well. Ported vs. full vacuum advance, that is a whole different story............. Today, my 71 is set up just like is was after I removed the stuff, back in 71, same carb and same dist. Bruce 1 Quote Link to comment Share on other sites More sharing options...
Paul Bell Posted May 11, 2018 Share Posted May 11, 2018 Electric fans can draw a lot of amps, some like 20 amps. This circuit won't be able to support that much current. Although there's good current available at the horn relay, I'd suggest you go direct to the battery for your fan feed. Fuse it of course. Quote Link to comment Share on other sites More sharing options...
ZeroMick Posted May 11, 2018 Author Share Posted May 11, 2018 Thanks everyone, got the answer I was looking for and learned something as well Cheers Paul, I've got a fused wiring harness ready to go in (with direct battery connect) the 12v with the key on is just for the relay. Electric fans can draw a lot of amps, some like 20 amps. This circuit won't be able to support that much current. Although there's good current available at the horn relay, I'd suggest you go direct to the battery for your fan feed. Fuse it of course. Quote Link to comment Share on other sites More sharing options...
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