chachee

Is there supposed to be a solenoid or something that kicks my idle up on my '85 12a when the A/C is turned on? I had to turn the idle up to keep this thing running. BTW The A/C is staying on the car. I need it, this is my daily driver.

CarlRx7

yes, its a part of the emission systems on the car, and something else on the carb. ask sterling or rx7carl, i know they know. =)

carl.

chachee

all emissions are still here.

Bob Holton

Big deal! in the summer you set the idle up to 110 to keep the AC working . In the winter set it to 112 to keep the engine running, The car is 20 years old and some things must be compensated for. like old people, that some of uou out there distain so.

Rx7carl

Look at the emissions removal tutorial if you can for some pics of this. Theres 2 components that need to work for this. First yes theres a solenoid that comes on when you turn on the AC. It then routes vacuum to the throttle opener. the throttle opener has a rod that moves upwards and pulls the throttle open a bit. The throttle opener is on the drivers side of the carb near the rear. Its a round black plastic ribbed housing with a single hose going to it and an adjustment screw in teh center. Below it is the rod that pulls up.

Stevan

iTrader: (17)

It's the white solenoid, and the throttle opener is #2 in the pic.

chachee

Great! Thanks for the help. I will check for vacume and solenoid operation on my lunch break tomorrow. I like having the A/C (working properly) on these hot days. The help on this forum is unbelievable.

FirstGen7

I have the same problem, and it's just because the "throttle opener" (as described by Haynes) or "idle up solenoid" has frozen up. I have a feeling it's just rusted and crappy, it IS 22 years old....

I hardly use the A/C anyway, but when I have to get rid of some fog on the windows it's really quite useful...so I'm just going to replace it. There's no way I can get this one to work, I've tried everything, it's stuck like a piece of coal in Al Roker's ***...

mar3

iTrader: (8)

Be careful when you're setting that adjustment screw, the bracket is one flimsy piece of metal...

Sterling

Chachee,

The AC compressor puts a significant amount of load on the engine. At idle, this load is enough to bog the engine down. In order to combat this problem, an "Air Conditioning Idle Compensation Valve" is used. It's a black plastic dashpot mounted on a bracket above the linkage on the right side (firewall side) of the carburetor.
On the bottom of this dashpot, an arm that is bent at a right angle sticks out and it is meant to make contact with some linkage on the primary shaft when the AC is turned on.
When you turn on the AC, an electric solenoid also turns on, and it allows manifold vacuum to suck on the diaphragm of the AC Idle Comp Valve. When this happens, it pulls that arm up, and then that cracks open the butterflies ever so slightly.

Three things come to mind as possible explainations...

1) A hose is cracked, cut, or disconnected, so the diaphragm isn't seeing manifold vacuum.

2) The electric circuit to the solenoid is not complete, causing the same problem.
(Less likely.)

3) The carb was rebuilt, tuned, or otherwise serviced, and the idle comp valve was never readjusted after the new idle was introduced.
This is the most likey cause.

Valve adjustment:

If you study the AC Idle Comp Valve you'll notice a threaded portion with a locknut. Loosen the locknut, and adjust the valve by simply turning it. The right-angled arm underneath will (should) rotate freely as you turn the valve.

Procedure:

Tune the carburetor idle to 750-850 RPM while the engine is warm. (This should include a proper timing tune-up.)

Unplug the electric coupler to the AC compressor clutch. Start the engine while warm, and turn on the AC. This will not turn on the compressor, an so no noticeable load (by comparison, outside light load of the fan) will be on the engine, but normally the idle should go right up. This is because the solenoid should open, exposing the AC Idle Comp Valve to manifold vacuum from the rat's nest.

With the engine idling warm, adjust the AC Idle Comp Valve so that it lifts the linkage up enough to make the engine idle at about 1200 RPM.
Dont lock the nut yet.
Turn off the AC. If the idle does not drop back down conciderably, then there is another problem. The idle may not drop back down to the original RPM, but you can adjust that later.
Turn off the engine. Hook the AC compressor clutch back up and start the engine. Turn on the AC. If the idle does not kick up, then there is another problem.

Turn off the AC, but leave just the engine running. Readjust the AC Idle Comp Valve until the engine idles at the appropriate idle RPM again. Tighten the locknut, and check everything again.

Basically, you're readjusting that right-angled arm so that it's barely making contact with the linkage. As soon as the vacuum solenoid kicks on, it'll lift that arm up which will lift open the primary butterflies just a tiny bit.


-I've never done this. I'm guessing at the proceedure. The only thing I can see that I may be wrong about is that continuity to the AC Idle Comp Valve solenoid may be broken by removing the AC compressor clutch coupler, but I doubt it.

Let us know how you make out.

chachee

You guys have thought of everything! I wish I could work on it tonight but its a little late. I have only had this car about 2 months and have found allmost everything in working order and it to be well cared for. All hoses look new or in very good condition. I am very supprised how nice this car is for being almost 20 years old! I am betting on the either the solenoid being stuck or the diaphram is out of adjustment. I will update tomorrow. Thanks again.

chachee

Well, it is all fixed now. Found the diaphram to be out of adjustment. I noticed when I adjusted it a lot it would make the idle jump up and down.? Anyway it works good now with a proper idle. Thanks for the help everyone!