Still trying to figure out this box - The 1947 - Present Chevrolet & GMC Truck Message Board Network

tylervalo · 09-16-2011, 05:00 PM

Anyone know what this might be? It's on an 85' K10, originally a 4.3 V6. Is it possibly part of the A/C system? The only connected wire goes over to the A/C box on the firewall.

tucsonjwt · 09-16-2011, 07:04 PM

Fast Idle Solenoid Relay?
I would go to the Rock Auto online catalog, enter your year, make, model and search under electrical/relay and look at all of the items that say relay. If you get a GM part number you can look that part number up on the AC Delco pigtail/connector catalog online to find an exact match for your part.

tylervalo · 09-16-2011, 08:58 PM

I believe you're right. Do I need that to run A/C or is there some way to bypass it?
Posted via Mobile Device

tucsonjwt · 09-16-2011, 10:03 PM

My guess is it is doing nothing now. So, I think it is designed to sense when the A/C is on and activate the fast idle solenoid to compensate for the drag on the engine when the compressor is on. On my 83, everything is hooked up properly - my relay is attached to the valve cover of my 454, but the idle does not pick up when the A/C is on. This does cause the engine to barely idle at a stop light, but the engine does not stall, so I don't mind. Sometimes I will rev the engine a little at idle if the engine starts to lope. I think the solenoid adjustment screw it is attached to is turned out all the way, so not engaging the throttle. I prefer not to have a fast idle and waste gas.
Bottom line, disconnect the wire to the A/C and see what happens. You can always turn the idle adjustment screw on the carb to get a higher idle during the summer when you are running the A/C - you will just burn more gas when the A/C is not running.

tylervalo · 09-16-2011, 10:21 PM

I actually don't have the A/C compressor yet (PO hacked this thing to crap) but I've been doing some wire clean up. That one green wire does run over to the A/C box somewhere though, I didn't know if that relay had to be there or if it can be bypassed.

tucsonjwt · 09-17-2011, 08:11 AM

A wiring diagram might help you. I would think if the green wire bypasses the relay completely, then it would not be needed for A/C operation. Most likely the PO bypassed the fast idle solenoid only, which is why the wires just to that relay are cut. As I recall, there is a green wire going to the A/C compressor also.

09-16-2011, 05:00 PM	#1
tylervalo Registered User Join Date: Sep 2011 Location: Knoxville, Tn Posts: 408	Still trying to figure out this box Anyone know what this might be? It's on an 85' K10, originally a 4.3 V6. Is it possibly part of the A/C system? The only connected wire goes over to the A/C box on the firewall.

09-16-2011, 07:04 PM	#2
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,189	Re: Still trying to figure out this box Fast Idle Solenoid Relay? I would go to the Rock Auto online catalog, enter your year, make, model and search under electrical/relay and look at all of the items that say relay. If you get a GM part number you can look that part number up on the AC Delco pigtail/connector catalog online to find an exact match for your part. Attached Images

09-16-2011, 08:58 PM	#3
tylervalo Registered User Join Date: Sep 2011 Location: Knoxville, Tn Posts: 408	Re: Still trying to figure out this box I believe you're right. Do I need that to run A/C or is there some way to bypass it? Posted via Mobile Device

09-16-2011, 10:03 PM	#4
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,189	Re: Still trying to figure out this box My guess is it is doing nothing now. So, I think it is designed to sense when the A/C is on and activate the fast idle solenoid to compensate for the drag on the engine when the compressor is on. On my 83, everything is hooked up properly - my relay is attached to the valve cover of my 454, but the idle does not pick up when the A/C is on. This does cause the engine to barely idle at a stop light, but the engine does not stall, so I don't mind. Sometimes I will rev the engine a little at idle if the engine starts to lope. I think the solenoid adjustment screw it is attached to is turned out all the way, so not engaging the throttle. I prefer not to have a fast idle and waste gas. Bottom line, disconnect the wire to the A/C and see what happens. You can always turn the idle adjustment screw on the carb to get a higher idle during the summer when you are running the A/C - you will just burn more gas when the A/C is not running.

09-16-2011, 10:21 PM	#5
tylervalo Registered User Join Date: Sep 2011 Location: Knoxville, Tn Posts: 408	Re: Still trying to figure out this box I actually don't have the A/C compressor yet (PO hacked this thing to crap) but I've been doing some wire clean up. That one green wire does run over to the A/C box somewhere though, I didn't know if that relay had to be there or if it can be bypassed.

09-17-2011, 08:11 AM	#6
tucsonjwt Registered User Join Date: Jul 2007 Location: Tucson, AZ Posts: 3,189	Re: Still trying to figure out this box A wiring diagram might help you. I would think if the green wire bypasses the relay completely, then it would not be needed for A/C operation. Most likely the PO bypassed the fast idle solenoid only, which is why the wires just to that relay are cut. As I recall, there is a green wire going to the A/C compressor also.

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