03-22-2021, 04:38 PM | #1 |
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Location: Jacksonville, FL
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A/C Idle solenoid?
72 Cheyenne Super, 350/350.
Apparently a prior owner did something creative with the wire for this. It runs from the switch to the fuse panel, into one of the unfused always on blades. So, essentially, it's always engaged, keeping the idle higher even if the AC isn't on. I'm guessing that wire should go to a different source, one that is tied to the A/C somehow. I've searched and seen different wiring diagrams; maybe I'm just not seeing where it should go. Thoughts? Have to replace the AC Diverter box and heater core... oh joy. But at least from what I've seen, the AC heater core is easier to do, and can be done from inside.
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1972 Cheyenne Super LWB, 350V8, AC, PS, PB, all original 46k survivor |
03-23-2021, 08:52 AM | #2 |
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Location: Austin
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Re: A/C Idle solenoid?
The solenoid should be always active with key in on/run position. The solenoid is not intended for the a/c. It is an anti dieseling solenoid. Curb idle should be set using the solenoid plunger, not the carb idle screw.
I BELIEVE that curb idle should be set to 550 rpms with a/c on and trans in gear. As a result, with a/c off the higher idle when in park can cause dieseling. The solenoid thus fully closes off air supply so dieseling cannot occur. So, I think people think the solenoid is an a/c idle compensator. Well, it sort of is since it allows a higher base idle setting to compensate for a/c and then prevents dieseling due to the higher base idle setting. |
03-23-2021, 02:58 PM | #3 | |
Mr. Cheyenne
Join Date: Jun 2020
Location: Kyle, Texas
Posts: 1,686
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Re: A/C Idle solenoid?
Quote:
I am getting my new NOS solenoid to see if I can get it to work for the a/c... easy enough to test with jumpers before dorking with the OEM wiring. Though I've read the solenoid isn't strong enough to push the idle up on its own. But testing will be fun regardless
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Richard '72 Chevy C10 Cheyenne *Super WHT/MED BRONZE/WHT SBC 350 | TH350 | LWB | AC | Buddy Seats Upgrades: Tilt | Front Sway Bar | Radio | Sliding Window | Bed Spare w/Lock Bed Rails | Full LEDs | Courtesy Lights | Tachometer | Glovebox Lock & Light | Head Light Relays | *Upgraded Fully Super Trim |
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03-23-2021, 05:24 PM | #4 | |
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Location: Jacksonville, FL
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Re: A/C Idle solenoid?
Quote:
Ordered the heater core, A/C selector box, and a new glove box liner since mine is all messed up from the prior owner. First order with LMC...
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1972 Cheyenne Super LWB, 350V8, AC, PS, PB, all original 46k survivor |
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03-23-2021, 05:33 PM | #5 | |
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Re: A/C Idle solenoid?
Quote:
If you don't want the high idle with a/c off, set idle the way you like it via the solenoid. When the compressor is engaged, idle speed will drop regardless. Or, you can wire the solenoid through a relay to engage with the a/c compressor. But, the idle will not increase unless you tap the throttle or the compressor engaged while the throttle was already depressed. Usually not a problem if using the stock compressor which does not cycle. But, if you were at idle (say at traffic light) and switched on the a/c then the idle will drop until you blip the throttle or move off. All this assuming the solenoid will not overcome the return spring. Those are my thoughts anyway. Last edited by Davidf; 03-23-2021 at 05:38 PM. |
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03-23-2021, 05:50 PM | #6 |
Mr. Cheyenne
Join Date: Jun 2020
Location: Kyle, Texas
Posts: 1,686
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Re: A/C Idle solenoid?
Hi Davidf - yes I do understand all of that 100% (I do not disagree with any of your points, at all) but it is nice to see it written out they way that I been thinking how this solenoid works from the factory and how I *might* want to try to make it operate. I have been mulling this over for quite a few months and reading up on this solenoid. A lot of people are used to how this would have worked with newer cars/A/C systems and not one where it was designed for anti-dieseling (me included at the beginning).
My stock R12 system as been replaced with R134a with a smaller and cycling compressor, for the record.
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Richard '72 Chevy C10 Cheyenne *Super WHT/MED BRONZE/WHT SBC 350 | TH350 | LWB | AC | Buddy Seats Upgrades: Tilt | Front Sway Bar | Radio | Sliding Window | Bed Spare w/Lock Bed Rails | Full LEDs | Courtesy Lights | Tachometer | Glovebox Lock & Light | Head Light Relays | *Upgraded Fully Super Trim |
03-23-2021, 05:55 PM | #7 |
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Join Date: Sep 2011
Location: Jacksonville, FL
Posts: 143
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Re: A/C Idle solenoid?
I may try this after the Turkey Run this weekend. Don't want to mess with it as it's running so good.
Saw on a Corvette forum, that you should adjust the solenoid to the idle you want (600RPM for my truck per the label) and then use the screw on the carb to set the idle BELOW that. Then when you disconnect the wire, idle should drop to 4-500 RPM. My A/C has also been converted to 134, but using original compressor.
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1972 Cheyenne Super LWB, 350V8, AC, PS, PB, all original 46k survivor |
03-30-2021, 08:08 PM | #8 |
Mr. Cheyenne
Join Date: Jun 2020
Location: Kyle, Texas
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Re: A/C Idle solenoid?
Had a little drama with the eBay solenoid. While it was clean as a whistle and the solenoid worked perfectly, the plunger was loose as a goose. Meaning it was finger loose and I mean loose to just touching it. I tried loctite to hold it in place and let it sit overnight but when I return from a test drive it backed in so much, I could hardly get into my garage because of no idle.
I figured I'd not hear anything positive from the seller and bought another one (the sale clearly said no returns/refunds on electrical parts). Then to my surprise the original seller reached out, understood my problem, was sorry, and sent me a replacement! He reported in his message to me that he double checked all the ones he had and sent me the best of the lot and more or less guaranteed it will stay put after adjustments. That's a fine eBay seller! I have my 2nd one installed - working great and requires a wrench to adjust it. Now I have the replacement coming in the mail, so I'll have a spare! Currently in OEM/Factory mode as anti-dieseling.
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Richard '72 Chevy C10 Cheyenne *Super WHT/MED BRONZE/WHT SBC 350 | TH350 | LWB | AC | Buddy Seats Upgrades: Tilt | Front Sway Bar | Radio | Sliding Window | Bed Spare w/Lock Bed Rails | Full LEDs | Courtesy Lights | Tachometer | Glovebox Lock & Light | Head Light Relays | *Upgraded Fully Super Trim |
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