engine and drivetrain Carb Idle Adjustment Question For A/c Systems

[Gil. H.]

I did a quick search, but didn't find anything specific.

I thought I had once read of either a certain Weber downdraft carb that had a vacuum or other type of circuit that would adjust the idle up slightly when the a/c compressor kicked in. Or perhaps a valve that can be added especially for a/c demands. I used my a/c for a bit yesterday and at idle the car stalled, works fine otherwise.So, just checking to see what the intelligentisia here might know.

Weber 32/36, stock.

Thanks.

 

[Napes]

I have always been told by the "experts" (incl. Carl Nelson) that you must just run your idle higher if you have A/C (as both my wife and my '02s do) if you don't want the car to idle too low when the A/C is on.  When you also have an automatic tranny you need to set it even higher.  If I want to see around 8-900 rpm at idle with A/C on (which it is a lot here in Southern Arizona) and the car in gear then I must have the idle up to around 14-1500 rpm when neither of those items are on or in gear.

 

Bob Napier

[landon]

I set mine @ 950-1000 rpm. I see about 750-800 rpm when the A/C is on with no real drivability problems or stalling.

[Mike Self]

Some years ago I installed a solenoid throttle positioner -- a small solenoid wired in parallel with the A/C compressor.  It was positioned on the old bracket that originally held the vacuum decelerator diaphragm on the 2bbl cars that prevented the throttle from snapping shut when the accelerator  was released, part of  the emission system.   

Don't remember the company name, but it's the same folks who make the anti-dieseling solenoid for Weber carbs. 

 

When the A/C was on, the solenoid would extend 2-3mm so that the idle stop on the carb linkage would hit the solenoid instead of the stop on the carb body, thus raising the idle 2-300 rpm.  The solenoid was mounted in an adjustable bracket so you could set the "A/C on" idle speed to whatever you wanted. 

 

It worked just fine for several years, then the solenoid died.  I found with my rebuilt engine that it was strong enough with the idle set at about 800 rpm that the A/C wouldn't cause stalling, so I never replaced it.  But I suspect they're still available, or you can find such a generic throttle positioner in a parts catalog and fabricate your own bracket.

 

cheers

mike

[Gil. H.]

Thanks guys for the info. Appears that adjusting the idle is the easiest way to go. But the solenoid option is interesting. Went online and the found the solenoid for around $25.00, making a bracket might be the challenge.

Idle adjustment for now.

 

Regards.

g.