{"id":5878,"date":"2025-12-06T11:30:02","date_gmt":"2025-12-06T16:30:02","guid":{"rendered":"https:\/\/stock.corvair.org\/wordpress\/?p=5878"},"modified":"2026-02-22T11:55:48","modified_gmt":"2026-02-22T16:55:48","slug":"corvair-ac-idle-speed-up-control-assemblies","status":"publish","type":"post","link":"https:\/\/stock.corvair.org\/wordpress\/2025\/12\/corvair-ac-idle-speed-up-control-assemblies\/","title":{"rendered":"Corvair AC Idle Speed-up Control Assemblies"},"content":{"rendered":"\n
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Collection of all six Corvair Idle Speed-up Controls<\/figcaption><\/figure>\n\n\n\n

Introduction and terminology<\/h2>\n\n\n\n

Corvair Factory Air Conditioning was a relatively rare option, available 1961-1967. Beginning in 1962, Corvairs with C.A.C. (Car Air Conditioning) were equipped with an idle control assembly designed to increase the idle speed when the compressor was running, to prevent engine stalling. Between 1962 and 1967, six different versions of the Idle Speed-up Control assemblies were produced.<\/p>\n\n\n\n

Note: Although Chevrolet’s official name for these units is “Idle Speed-up Control Assembly”, they are more commonly known as “Fast Idle Solenoids”. Hereafter in this article I shall refer to these units by the abbreviation “ISCA”.<\/p>\n\n\n\n

1961<\/h2>\n\n\n\n

Corvair Air Conditioning was first introduced in March 1961, using a Frigidaire A5 compressor (painted green to identify it as a reverse rotation unit). This option did not initially include an ISCA; however, Chevrolet TSB DR #513, issued on January 15, 1962, directed dealers to install one if the owner complained of engine stalling or rough idle. The ISCA to be installed was identical to those installed on all 1962 CAC Corvairs.<\/p>\n\n\n\n

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1962<\/h2>\n\n\n\n

ISCAs were required on all 1962 CAC Corvairs, but the device was not unique to Corvair. Other GM cars also used them (with different mounting brackets), as pictured below:<\/p>\n\n\n\n

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1957-61 Cadillac Idle Speed Control Assembly<\/figcaption><\/figure>\n\n\n\n
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7020986 – 1962 Chevy II Idle Speed Control Assembly<\/figcaption><\/figure>\n<\/figure>\n\n\n\n

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The 1962 Corvair version is part number 7020095, and has two wires exiting the phenolic base; one with a bare ring terminal that is attached to ground, and the other an insulated male Packard 56 terminal that connects to the compressor clutch.<\/p>\n\n\n\n

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1962 Assembly manual<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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7020095 – 1962 Corvair Vacuum-Electric “Pusher” with dual-wire solenoid, mounts on right side condenser support<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

How it works<\/h2>\n\n\n\n

This is a vacuum-electric unit with a piston that extends to push on a finger mounted to the accelerator linkage whenever the compressor clutch is activated; hence, this device is commonly called the “pusher” unit. The device consists of a housing for the solenoid integrated with the vacuum ports and the diaphragm housing. Inside the diaphragm housing is a powerful spring which pushes the piston and its attached rubber diaphragm. A small brass rod valve attached to a ferrous metal disc is inserted in a hole at right angles to the vacuum port. A solenoid coil with a small spring inside is secured to the housing with two screws. <\/p>\n\n\n\n

Whenever the compressor clutch is inactive, the solenoid coil is also unpowered, allowing the small spring to push the metal disc away from the coil, thereby seating the brass valve and opening the vacuum port to the diaphragm. When the engine has sufficient vacuum (engine is idling), the vacuum overcomes the push of the large diaphragm spring and retracts the piston away from the throttle linnkage finger. <\/p>\n\n\n\n

Whenever the compressor clutch is active, power is supplied to the solenoid coil to lift the metal disc, pulling the brass rod up. This vents the diaphragm housing and blocks the incoming vacuum port, causing the diaphragm spring to push the piston forward to press on the accelerator linkage and speed up the idle. Note that the solenoid coil is powered whenever the compressor clutch is powered, and this happens at any engine speed; however, only at idle is the accelerator linkage in position to be affected by the extension of the piston.<\/p>\n\n\n\n

The basic flaw in this design is that anything causing loss of vacuum to the device (blockage or leakage in the hose, etc.) will result in abnormally fast idle when the AC is not running, as the piston will always remain in extended position and contact the accelerator linkage at idle.<\/p>\n\n\n\n

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1963<\/h2>\n\n\n\n

The only change in 1963 was the elimination of the ground wire. It was replaced by a brass “finger” riveted to the phenolic base, grounded by way of one of the base attaching screws. In spite of the modification, it retained the same part number, 7020095.<\/p>\n\n\n\n

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1963 Assembly Manual<\/figcaption><\/figure>\n<\/div>\n\n\n\n
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7020095 – 1963 Vacuum-Electric “Pusher” with single wire solenoid, mounts on right side condenser support<\/figcaption><\/figure>\n<\/div>\n<\/div>\n\n\n\n

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Replacement Kits<\/h2>\n\n\n\n

1962-63 ISCAs used very small brass rod “valves”- approximately 1\/16″ diameter. Over time, these valves were prone to wear, breakage, or separation from the metal disc, any of which would render the unit inoperative. Back in the day, replacement kits for both the solenoid and diaphragm units were available. Other than the part numbers, I have found no other information about these kits:<\/p>\n\n\n\n