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Idle Compensator (A/C)


TheBMan

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Trying to get the A/C in my 72 working as good as possible. One thing I have noticed is that the engine does not idle "up" when the A/C is running. In the factory service manual, in the A/C section, it mentions an "Engine Idle Compensator" and says the following: "this additional aid to prevent stalling during prolong hot weather periods is included with all air-conditioned vehicles. The idle compensator is a thermostatically controlled air bleed which supplies additional air to the idle mixture. On V-8 engines, with factory installed air conditioning systems, the compensator is located within the carburetor and is accessible when the engine air cleaner is removed."

I know where this valve is located but the manual doesn't give any detailed information on when or how it operates nor any procedure to test it. It's not even clear if this device is used to "up" the idle speed when the A/C (compressor) is on.

Does anyone have any information about this and/or how the idle speed is controlled with the A/C compressor is engaged?

Thanks!!

idle-compensator.jpg

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There was a Electric Solenoid attached to the Factory carb that with A/C on/running, that Solenoid would engage increasing RPM so that there would not be a stall from the engine.  I will try and find the diagram/pic showing it on the Factory carb and Post unless another had already answered your question with pic's.  I am not aware of any adjustments needed with Solenoid attached.

Doug

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12 minutes ago, 72-CLASSIC_RIDE said:

There was a Electric Solenoid attached to the Factory carb that with A/C on/running, that Solenoid would engage increasing RPM so that there would not be a stall from the engine.  I will try and find the diagram/pic showing it on the Factory carb and Post unless another had already answered your question with pic's.  I am not aware of any adjustments needed with Solenoid attached.

Doug

Thanks Doug! Unless I'm mistaken, I have the solenoid that I think you're referring to. It's not intended to increase the idle speed with the A/C running, it's an anti-dieseling solenoid. It is always engaged when the key is on. You use it to adjust the idle speed. When you turn the key off, the solenoid de-energizes and allows the throttle plates to close completely, shutting off air to the engine to prevent engine run-on or "dieseling". Not much of a worry with the quality of today's gasoline but was very helpful back in the day!

If there is a different solenoid that I'm not aware of, yes, please lay it on me! Thanks!!

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I've done a lot of searching and reading and have found that this part is simply a temperature-sensitive strip of metal that deforms when it gets hot and opens a small air bleed hole into the carburetor. Essentially it's a small vacuum leak intended to raise the idle slightly. It's not connected to the A/C system in any way, it was just something they put on A/C cars because of the increased load and temperature caused by the A/C.

I guess there was no way (from the factory) to increase the idle speed slightly when the A/C kicks on.

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I have a solenoid on my carb that increases the idle when I turn on the AC. I think it is an Eldabrock product at least the bracket is made by them. Works great and looks like the factory installed anti dieseling solenoid

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@Leghome - great info! Thanks! I read this in the Edlebrock install instructions. It sounds like it doesn't engage until you stab the throttle once with the a/c on. Is that the case for you?

"NOTE: The solenoid will not engage the throttle lever and increase idle RPM until the throttle pedal depressed at least one time. Depressing the throttle with the air conditioning switched ON will activate and engage the plunger. The plunger will disengage when the air conditioning is switched OFF.”

I originally tried using the anti-dieseling solenoid for this (wired it into the compressor) but the solenoid didn't have enough force to move the throttle unless I stabbed the throttle once. Then it would be engaged and active until I turned the a/c (or car) off. This seems a bit hackey to me. I want the RPM to raise without any intervention from me.

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When I turn on the AC the idle increases without have to race the engine. I got this solenoid form my son in-law and he told me it came off of one of his Camero's and was for AC idle speed increase when AC turned on.  My memory does not always store what I have been told correctly but I think I is right

 

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