Can ignition switch cause 560sl high idle???

[560slsteve]

HI--I still have a problem with my 87 560sl with 130k miles. It began to idle high about a week ago, and i hope to get some advice on this great site.
I have read with great interest all the posts on high idle, and have checked on each procedure---TPS(throttle position switch), ICV(idle control valve), ICU(idle control unit or speed control), etc. When I checked voltage on ICV, it was 0. I cleaned and connected the ICV with 12V and valve worked. I figured the ICU wasnt sending any voltage to the ICV to reach the correct idle, so the ICU must be bad. Another interesting thing was the car only did this initially after it was hot---idle was correct upon start up until today.
So I'm about to bite the bullet and go buy a new ICU, when something clicks, and she idles like a sewing machine. Voltage across the ICV was 5V. I took off the 3-prong TPS connector and it idled up 300rpm, like it should. I disconnected the ICV completely and it revved way up, and went back to normal when re-attached. So i'm guessing the ICU and ICV and the TPS are working properly.
I drove the car some and then the AC stops. I get back home and put 12 V to the AC clutch and it comes back on, so i know the clutch works. After a few minutes the car goes into high idle again. what the>>>>??? Voltage reading at ICV was zero again, and disconnection everything had no effect.
Am i missing a sensor somewhere thats telling this computer that its overheating or something, and to shut off the AC and idle up to cool?? The AUX fan never comes on (i jumped it and it works) and the car is running at normal temp. I have pulled the connector on the coolant temp. sender and nothing happens. I have checked the OVP relay and the 10 amp fuse is ok. I checked all the solder joints on the ICU and they all checkout.
While the car was running i pulled the ICU out and it didnt make a difference, so i figured the unit wasnt getting any power. All the fuses are powered when the switch is on. What am i missing here?? Could the ignition switch be bad somewhere and not supply power to the ICU like it did the AC compressor?? I have read about the mercedes switches, and on this car we had to "jiggle" the switch to get the AC compressor on, but not recently and it's not working now. I have replaced the AC control unit before, which was a waste because the low pressure switch was bad and was doing it's job. I dont want to replace the ICU and do the same thing. Any thoughts would be appreciated. thanks and I'll keep reading.