Markwz11

I just purchased a '74 Cutlass Supreme that has been in storage for MANY yrs. Although it only has 34K original miles, it has had a lot of lines and hose replacements so no worries there...yet.
While tuning the Rochester Carb/choke, I noticed the A/C Idle Stop Solenoid was not kicking off... it was in constant "A/C On" mode, whether the A/C was on or not. I thought it was bad, so I removed it and as soon as I removed it, the "piston" deactivated. Being a little confused, I decided to test it out. Knowing that it "self grounds" when screwed onto the carb and having only one "live wire" connector, I grabbed an alligator clip wire, attached it to the solenoid body to ground it, and connected the lead wire to the battery... and the piston activated... I removed the lead, and the piston let go... now I'm thinking the solenoid is fine.
So I grabbed my circuit tester and connected it to the carb (for ground), stuck the prong into the connector wire on the engine and as soon as I turned the ignition key to the "ON" position...my tester lit up! I was expecting it to light up as soon as I turned on the A/C, but the wire was live in the "ignition on" mode.
Is this right? If the connector wire on the engine is live as soon as you turn the ignition on, how would the solenoid know whether you've turn on the A/C or not? Can someone advise me to the next steps in repair, testing or finding the problem. Thank you.

joe_padavano

That's because it's not an A/C Idle Stop Solenoid, it's an anti-diesel solenoid. It holds the idle speed at the correct level when the engine is running. As soon as the key is turned off the solenoid retracts so the throttle blades close all the way to prevent dieseling.

Markwz11

Thanks Joe... my apologies. This is what a local mechanic told me, only he said he thought it was bad and I should search for one "on-line", since no dealer would cary one.
With that being said, is there an "idle up solenoid" to increase the idle when the A/C compressor kicks in or is this handled elsewhere? Thanks for your help.
Mark

joe_padavano

I don't think there's a separate solenoid for your car. The use of the anti-diesel solenoid allows the idle to be set at a level that accommodates both A/C on and off conditions. Without the anti-diesel solenoid, that level would likely cause run-on when you shut the engine off. That's why you have the anti-diesel solenoid.

Markwz11

HHMMMMMM, well, now I guess I need to get an aftermarket TACH so that I can make sure the idle is set correctly. There is a definite "idle down" when the A/C or Defrost is kicked in. I've only had the car for a couple months now and am close to burning my first complete tank of gas. After the basic minor tuning (plugs, wires, cap, etc...) I have it running MUCH better, with the exception of this one detail. In your opinion, is this normal or common? Thanks.

Lady72nRob71

A slight drop in RPM with the AC on is okay, as long as the car still drives well and is in no chance of stalling.
In both my Olds, there is a slight decrease but never an issue. Neither have idle up controls.

RROLDSX

When I was broke and going to college my idle stop solenoid stop working so I stop the engine from dieseling by hitting the gas and stalling the motor after the ignition was off. This worked fine for a while in the cold weather but one day instead of stalling it revved up and suddenly there was a huge explosion! Darn near lifted the car! The unspent fuel ignited and blew my muffler up like a huge bomb!

That's how I learned what an idle stop solenoid does....also, this car had no air conditioning whatsoever.

Markwz11

Thanks everyone. I've learned that instead of having an Idle Up Solenoid, I have an Anti Dieseling Solenoid. With that being said, I just need to know how to adjust the idle at a level that can accommodate the A/C whether on or off. I only know of one idle screw on the side of the carb by the linkage. I've read idle specs of 650 to 850. I'm going to assume that its based on individual preference. ???