Overvoltage relay.

[msar]

Could someone please tell me what the overvoltage relay does? I've seen it in the manual but am uncertain if the problem I'm having could be caused by a faulty OVR.
My 560sl's idle occasionaly (1x per week) goes to 1700rpm. I got lucky tonight and experienced the problem while working on the car. I put my volt meter on the pins to the idle valve without actually disconnecting the valve. The idle actually fluctuated between normal (650rpm) and high (1700). Correspondingly, the meter showed 5v @ 650 and 0 @ 1700. Interestingly, when I remove the plug from the valve, everything seems to reset and the idle goes back and remains normal until the next time. Other symptoms: this only occurs when the engine is warmed up, I've tried tapping the valve to see if it's getting stuck - no change, I pulled the control module and saw no burned transistors etc.
It seems that the way the valve works is that it closes when power is applied to it. My meter readings show that the power to the valve is fluctuating. Does this narrow the problem down to the module or OVR? Thanks for advice. Mike