1974 A/C Idle solenoid

[Petter T.]

Hi all.

Got the A/C system checked and filled the other day and now I get cold air.
The A/C Idle Solenoid has not been connected since rebuild of carburetor, but I mounted it back on today.
I did a very short test (did not run engine to working temperature, but choke was off), as far as I did the test, the solenoid were engaged all the time with the A/C of (Compressor not running).

In my head the A/C Idle Solenoid should not engage until A/C is turned on.

What is the correct operation of the A/C Idle Solenoid?

Br
Petter
1974 L82 Auto A/C

[Robert S.]

Re: 1974 A/C Idle solenoid

I have a 74' with A/C. I assume you are talking about the solenoid mounted on the left side of the Quadrajet which sets the engine idle speed when the engine is running. That solenoid is not related to the A/C system. It is actually an anti-diesel device. When the engine is running the carb throttle position is set by the solenoid. When the engine is shut off the solenoid is deactivated and the solenoid shaft slide back allowing the throttle to close further. Without this solenoid a hot engine will often run-on (diesel) after the key is turned off.

[Petter T.]

Re: 1974 A/C Idle solenoid

Hi Robert, thank you for pointing in the right direction.

After having searched the net it seems that there existed both anti dieseling and idle increase solutions. Anti dieseling would explain why my solenoid always is engaged with ignition on.

Need to adjust idle once more...

Br
Petter

[Tom R.]

Re: 1974 A/C Idle solenoid

Hi Robert, thank you for pointing in the right direction.

After having searched the net it seems that there existed both anti dieseling and idle increase solutions. Anti dieseling would explain why my solenoid always is engaged with ignition on.

I suspect your 74 L82 M40 also has a TCS solenoid mounted opposite of the anti-diesel solenoid and manages vacuum advance when present and operating as engineered. Do you have it?

[Petter T.]

Re: 1974 A/C Idle solenoid

Yes, the TCS sits on the passenger side of the intake up front.