My mechanic told me that i might need a electric solenid that bumps up the idle when the ac is on i have a 72 cutlass with a 455 motor.if so where does it go

 

should show up in the shop manual assuming you have one..

 

if your car was originally an A/C car it should already have one and just need replaced or adjusted. it is mounted on the front driver side of the carburetor (assuming you have the original carb setup) it is the only electric plug going to the carb. when the A/C is on it pushes on the flat area of the throttle linkage just in front of where the cable hooks to.

 

It was an Original ac car but with a 350 in it.When i bought it has a 455 in it.If the wire is not there where do i pick it up from and what is the actual part called thanks

 

I don't believe this to be true for 1972. If it had anything, it was probably just a dashpot. And whether or not a dashpot was installed by the factory was likely influenced not only by the presence of A/C but also 350 vs. 455, 2 bbl vs. 4 bbl carb, and manual vs. automatic transmission.

If you install a solenoid, you want it to be engaged whenever the A/C compressor clutch is engaged. Whether or not you can do this by connecting it to the same contacts of the same relay depends on how the clutch and solenoid operate -- switched 12 V or switched ground.

 

the 72 that i just sold had one. the power came from the wiring at the compressor. the solenoid was grounded on the carburetor and the only wire on it was a power wire and it connected to the power wire at the temperature switch at the compressor.

i think i have some NOS harnesses that hook to the compressor and solenoid. i will look for them and take a picture for you to understand better how they hook up.

 

now that i think about it, the 72 did have one but the wiring i explained was on another car. i do not remember how the 72 was wired. but for the most part, you just need a power wire that is energized when the A/C is on.

 

So what was the magic formula to determine what car option combo got the idle-up solenoid?
My 72 350 never had one and it idled fine with the AC on...

 

my car was a 72 350 2bbl built in california.