'74 won't idle with A/C running - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**MJN** · 06-17-2007, 05:49 PM

My '74 pickup won't idle with the A/C running. According to the factory shop manual, there is an idle air compensator on all trucks with factory A/C. Since I put a rebuilt Q-jet on I'm not sure if this carb has that part. Does anyone know what it looks like or if all carbs came with them and mine just needs to be adjusted?

Yankeelights · 06-17-2007, 07:15 PM

Check out: http://www.acefuelsystems.com/service.htm

5th photo down; lower left side of the photo you can see the fast idle solenoid, shiney zinc body and bracket with a brass hex adjustment head. There should be one wire going to it.

**MJN** · 06-18-2007, 07:59 PM

is there a difference between the fast idle solenoid and the idle stop solenoid? In all my parts books I can't find any fast idle, just idle stop. I assume when wiring the fast idle solenoid you would tie it into the A/C wire so they're both energized when the A/C is switched on.

Yankeelights · 06-19-2007, 08:12 PM

They're one in the same solenoid. Yes, when the compressor is on, the solenoid should be on. Adjust the hex head on the solenoid for proper idle speed with the AC on.

These solenoids can also be used to prevent engine run-on by setting it to proper idle while energized with an ignition-on power supply; when you turn off your engine the solenoid cuts out and cuts off air to the engine.

~ Dave

06-17-2007, 05:49 PM	#1
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 3,051	'74 won't idle with A/C running My '74 pickup won't idle with the A/C running. According to the factory shop manual, there is an idle air compensator on all trucks with factory A/C. Since I put a rebuilt Q-jet on I'm not sure if this carb has that part. Does anyone know what it looks like or if all carbs came with them and mine just needs to be adjusted? __________________ '51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com

06-17-2007, 07:15 PM	#2
Yankeelights Registered User Join Date: Jun 2007 Location: NW Pennsylvania Posts: 92	Re: '74 won't idle with A/C running Check out: http://www.acefuelsystems.com/service.htm 5th photo down; lower left side of the photo you can see the fast idle solenoid, shiney zinc body and bracket with a brass hex adjustment head. There should be one wire going to it.

06-18-2007, 07:59 PM	#3
MJN Registered User Join Date: Feb 2000 Location: Maquoketa, Ia/ Orr, Mn Posts: 3,051	Re: '74 won't idle with A/C running is there a difference between the fast idle solenoid and the idle stop solenoid? In all my parts books I can't find any fast idle, just idle stop. I assume when wiring the fast idle solenoid you would tie it into the A/C wire so they're both energized when the A/C is switched on. __________________ '51 South Bend Model "9A" '56 Chevy 3600 NAPCO '74 Chevy Cheyenne Super K20-restored on 37's '72 GMC Sierra Custom K2500- in progress '08 GMC Envoy Denali '12 GMC Sierra 2500HD Denali '17 GMC Yukon XL VCCA member #58596 http://www.nohrco.com

06-19-2007, 08:12 PM	#4
Yankeelights Registered User Join Date: Jun 2007 Location: NW Pennsylvania Posts: 92	Re: '74 won't idle with A/C running They're one in the same solenoid. Yes, when the compressor is on, the solenoid should be on. Adjust the hex head on the solenoid for proper idle speed with the AC on. These solenoids can also be used to prevent engine run-on by setting it to proper idle while energized with an ignition-on power supply; when you turn off your engine the solenoid cuts out and cuts off air to the engine. ~ Dave



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