A/c creates high idle

[Spoonbill]

So I was sitting the driveway reading some emails and I turned on the a/c and the idle went double as to what it was before I turned the a/c on. It has never done this before. What would cause this to happen?

[bd]

Misadjusted idle speed solenoid.

[Spoonbill]

That would make it just all of a sudden? Please remember it has only 66,000 original documented miles and all the parts are original except for the tune up I did last November

[Spoonbill]

Is this also called iac valve??

[bd]

Provide the year, make, model of the truck and the engine/transmission combination.

[Spoonbill]

I just put a new iac valve on about 3 months ago. Truck is an 87 r10 305tbi 700r4

[bd]

Is the amber Service Engine Soon light coming on?  Are there any stored trouble codes?  Does the A/C work?

[Spoonbill]

No warning lights have ever came on. A/c works awesome, it is still the original r-12 one that came on it. It is expensive but well worth it cause it so much colder than 134. To check for codes could I just take it up to autozone and have them hook that hand held scanner up to it?

[bd]

That would be a good starting point.  Or, you can retrieve any stored codes yourself using a paperclip; see OBD I code retrieval and decoding.

Does the service engine soon (SES) dash lamp illuminate when you switch on ignition, before starting the engine?

Do you have a digital volt ohmmeter?

[bd]

You should also begin to familiarize yourself with the 1987 Light Duty Truck Fuel, Drivability and Emissions manual.  It is an invaluable, essential tool.

[Spoonbill]

Yes it comes on before I start the truck but as soon as started it goes out. I don't know anything about this stuff yet, I'm still in the learning phase so I will let autozone get the codes for me so that I will know it was right