ac solenoid?

[PowerdbyChevy79]

whats up brothers.. have an issue and ive never encountered this before.. I have a68 with a 400 small block with a thumpr can, 650 edelbrock, vintage air setup nothing fancy.. my issue is I have it idled at 900 rpm when I put it in gear it goes down to about 700-750 rpm.. but when I turn my ac on.. it drops to about 500 rpm.. sometimes even dipping to the 400.. ive messed with the timing but nothing helps.. my buddy told me that I need a ac solenoid.. never heard of it.. does anybody here have any experience with this issue

[Davidf]

A/C solenoid is wired in with the a/c compressor. When the compress clutch is engage, the solenoid mechanically opens the carburetor throttle valve. So, you need to purchase a suitable electric plunger type solenoid, fabricate a suitable bracket so that the solenoid pushes/pulls on the throttle arm, and wire it up. You adjust the solenoid in the bracket to get the correct engagement to maintain a steady idle with a/c on or off.

Hope that helps.

[davepl]

Our trucks don't have them, and my idle drops a lot too. If you have a big cam, vacuum leak, not enough timing, or are otherwise out of tune it can cause a big drop.

I don't know how big the thumpr cam is, but that's probably the culprit. Other than running more base timing I don't have a great suggestion, unfortunately.

You could add a trinary valve (I guess we have expansion valves so a binary maybe) that kicked up the idle with a solenoid you take off some other vehicle. Or maybe there's a way to wire it to the connector on the compressor, so that when the clutch is activated the solenoid kicks up the idle speed? That's probably your best bet if you can't solve it otherwise.

Ideally if you could find one that electrically tied into the clutch wires on the donor vehicle you'd be far ahead.

[AASmedic]

Does anyone know the original part number of the solenoids used in these applications? I have found a bracket and there are many solenoids but I would like to find an original AC Delco part. I have a 350 with a 4 barrel carb.

[c10ss69]

Holley makes a solenoid for this. Part #46-74 but you would need to make a bracket for use on an Edelbrock. They have a bracket for 4150 carbs #20-9 and a bracket for 4165 & 4175 style carbs #20-47. This is the route I plan to go.

[n33k0]

My truck has a Holley solenoid and bracket. The solenoid is not strong enough to bump the throttle on its own. When the solenoid engages the plunger will extend about 3/4 of the way until it hits the throttle, then I need to press the gas to pull the throttle back, giving the solenoid enough room to extend fully, then the plunger is strong enough to hold the throttle at the new position. I've read this is common with these solenoids, and I haven't done much research to see if there is a solenoid strong enough to bump the throttle on its own.

[c10ss69]

Originally Posted by n33k0

My truck has a Holley solenoid and bracket. The solenoid is not strong enough to bump the throttle on its own. When the solenoid engages the plunger will extend about 3/4 of the way until it hits the throttle, then I need to press the gas to pull the throttle back, giving the solenoid enough room to extend fully, then the plunger is strong enough to hold the throttle at the new position. I've read this is common with these solenoids, and I haven't done much research to see if there is a solenoid strong enough to bump the throttle on its own.

Thanks for the heads up.

[AASmedic]

Sorry, guess I should have specified. I have a 4 bbl Rochester

[hdff]

Originally Posted by AASmedic

Sorry, guess I should have specified. I have a 4 bbl Rochester

I had a 78 corvette with a quadrajet and it came with the solonoid so you might check a corvette parts place. I bought a replacement for it a few years ago. I might have got it from the parts place at my local Chevy dealer, I have CRS so I don't remember for sure, getting old sucks!