I just put in a reman a/c compressor, new VIR unit, new hoses, and did the 134A conversion in my 1974 Camaro LT. It has the 350 2 barrel motor. It blows cold and all of that good stuff, so heres my question:
I also put a new Idle stop solenoid (the solenoid on the side of the carb) because the old one was shot. When I turn the car on, the solenoid energizes and I have it tuned to the right specs. Now, when I turn on my a/c, it doesnt extend out to bump the idle up. I thought maybe I had adjusted it wrong, but Ive checked it at least 5 times now. How can I get it to work right?

I do not understand how it can energize, but when I turn the a/c on it does nothing. Is there something I am not getting? First to tune it I used the specs on the radiator, and double checked it with the chilton manual, and ive repeated that process a few times now.

I know that the solenoid is connected to the a/c clutch, so I checked all of the wiring coming out of that and it looks fine. Anybody have any ideas? I posted this in the troubleshooting section too, I am not sure which forum would get more traffic.

Thanks in advance for any help.

I am confused by your description. It energizes (as in it does operate), but then doesn't work???

Am I understanding your description in that it energizes when the car is turned on and just stays on? This is incorrect- it is either on or off- it is not a multi-stepped setup. When power is applied to it by the AC system relay- it is supposed to energize, extent the plunger and bump up the idle. When no power, it does nothing. It should not have power when the car is turned on unless the AC is also turned on.

OK.. with the A/C off and the solenoind unplugged....set the idle to where the engine idles very slow(check the RPM specs). this is curb idle if i remember right.
Now,plug up the solenoid and give it enough gas to let the plunger pop out. turn on the A/C and set the Idle to the specified RPM.
The purpose of this solenoid is to hold the idle speed...then when you cut the ignition off it cuts the idle so the engine will not keep running (Dieseling) The A/C wiring has nothing to do with that solenoid.

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to Clarify a point.
the curb idle is set with the screw on the carb.
the actual idle is set by adjusting the solenoid plunger length. The idea is when you turn off the key it basicly shuts the fuel off.
Example: if you set the idle to 750 RPM in gear with A/C on then went to park the idle would increase to 1000 RPM or more. Without the solenoid the engine would Diesel(keep running) after you turned the key off.

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<font face="Arial,Verdana" size="2">Originally posted by dgwar:
OK.. with the A/C off and the solenoind unplugged....set the idle to where the engine idles very slow(check the RPM specs). this is curb idle if i remember right.
Now,plug up the solenoid and give it enough gas to let the plunger pop out. turn on the A/C and set the Idle to the specified RPM.
The purpose of this solenoid is to hold the idle speed...then when you cut the ignition off it cuts the idle so the engine will not keep running (Dieseling) The A/C wiring has nothing to do with that solenoid.

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That solenoid is to hold the idle speed- ONLY when the AC is powered. Curb idle is set with it off- you're correct- but this is for all non-AC driving- the solenoid actually bumps up the idle speed for use with the AC to keep the engine from stalling with the extra load- it's purpose has nothing to do with preventing run-on/dieselling- this does occur- but it is a secondary function that exists by default in the design- I believe GM got smarter by the early 80s and actually changed the official part name to "AC idle solenoid" because, as you've indicated, it gets a bit confusing with the name "idle stop solenoid" (the "idle stop" in reference is actually the "stop" point for the throttle arm- i.e. it is called an "idle stop solenoid" because it would change the idle point by altering the throttle arm "stop" (like the standard set screw for curb idle).

I guess that is my problem then.

I originally understood it to work where you set it without it engaged, then when you turned the a/c on it would kick up. After reading a dozen books I got confused along the way.

So I guess my problem now is that it is energized all the time. Is it connected to any kind of a switch or relay anywhere? I do not see why it would be energized all the time =/

If I recall correctly (and I may not- so you probably should check this)- the ignition-on power wire that eventually leads to the solenoid is interrupted by a relay that is connected to the main A/C compressor relay- actually in-line before this relay- the same "power on" signal from the AC control switches both relays. I also seem to recall seeing somewhere that the main compressor relay also controlled the solenoid- but don't quote me on that.

I believe the solenoid is connected to the a/c clutch...so when the a/c comes on so does it...but since the a/c isnt on full time (which means the clutch is obviously working) then I don't see what could be making this thing not work.

Even if I unplug the harness from the a/c the solenoid still works, so maybe that is something I should check into. I see where the wire connects to the clutch, and from there goes somewhere else, so I guess I need to see where that goes to. I can only recall one wire dangling under my dash, but it has the same kind of connector that goes to the solenoid. I'll try to look at that next.

Thanks again for all of your help so far Eric and dgwar.

There's at least 3 types of these solenoids to my knowledge and they all have different functions. One is to set the idle speed and drop the butterflies closed further when disengaged (my 2bbl truck carburetor had one) so that the engine does not diesel. The second type is to bring the idle speed up when the A/C is engaged. My caprice has a third type that energizes only under certain conditions to keep the throttle blades from snapping shut all the way to reduce emissions. My caprice has only heat, no A/C.

In your case you only want that wire to get voltage when the A/C compressor's clutch is actually engaged and dragging on the engine. This will happen at all engine speeds, but it only affects idle speed by raising it slightly. You can hear it at work because it will kick on and the enging idle will come up. I would check your wiring path all the way through the system for the wire and see what it is connected to. You should be connected to the A/C clutch power somewhere along the line.

The idle stop solenoid on a/c and auto equiped cars is supposed to increase idle with the a/c on. When the solenoid is energised it will only kick up the idle if the throttle is off idle. The solenoid is wired into the a/c compressor circuit and is energised with the a/c on. Later years had the wiring before the pressure switch on the accumulator.

Again,if you're expecting the solenoid to bump up the idle speed with the engine at idle and a/c on, it normally wont. The coil is too weak to do so. It will kick out when the throttle is off idle.

John

<font face="Arial,Verdana" size="2">Originally posted by 79ZED:
Again,if you're expecting the solenoid to bump up the idle speed with the engine at idle and a/c on, it normally wont. The coil is too weak to do so. It will kick out when the throttle is off idle.

John </font>

If your coil doesn't kick the idle up then it probably needs to be replaced. That's the function of this thing. I've had GM vehicles that it worked like a charm. I don't think he's wired up properly based on the fact that it energizes on the key. Given the fact that he has a 2bbl carb I suspect he's got a throttle stop solenoid, not the one that increases the speed when the A/C goes on.

My car came with ac so i better have the one for the ac.

It definetely has enough power to kick up at idle...it would be pointless otherwise. The first one I bought would only kick up if blipped the throttle. I think it might have been a different one like 73454 was saying, it had a different wire lead and when I took off the rubber boot it looked different as well. The second one I bought is the exact same as the one I originally took off of the car. This one is solid as hell, whereas the other one even when it was energized I could push it down with my finger.

As soon as the key is to the on position it does kick up, so I guess that is my problem.

I wish I did not have to work tomorrow, I want to fix this thing =/

it may not be an AC idle up solenoid.
It may be an ANTI-DIESELING Solenoid.

Disengaged it should allow the car to drop to 300 rpm or die.
Engaged it should idle at 600 or so rpm.

Set it high enough that when the compressor is on the car is still smooth and just don't worry about it.




[This message has been edited by hhott71 (edited May 19, 2005).]

When I put a hotter cam in my Z many years agao, I purchase a brand new GM solenoid for the purpose of bringing up the idle with the a/c on. In 1979 GM only put the solenoid on a/c auto equiped cars. The wiring for the solenoid was already installed from the factory, just a matter of bolting the solenoid on and plugging in the connector.

The solenoid would not kick up the idle with the throttle closed, only if the throttle was opened. Tried another new solenoid with the same results. Needless to say, I returned them to the dealer.

John

hhott- I dont want to set it like that, because the way mine is working right now if the a/c is off then it will be trying to idle at about 900 in drive instead of 600. every bit of gas mileage I can get I will take.

79zed- Mine engages fully at idle. My only problem now is trying to get it to only come on with the a/c.

<font face="Arial,Verdana" size="2">Originally posted by Mayhem74:
Mine engages fully at idle. My only problem now is trying to get it to only come on with the a/c. </font>

Then you need to wire it to the same circuit as the A/C clutch power.