500sl blower controller troubleshooting
 

I've seen some information on this problem on the forum, but need a little more help. We have a 99 sl and the AC blower is intermittant. Sometimes when you start the car the AC runs fine, then it will quit, then start again on its own. I can feel the cold air under the dash and have already confirmed that the evap sensors are in parameters. The blower does not stop abruptly or make noises and starts right up when it works. Most likely not the motor. The only things left are the AC control and the blower controller. The AC control has no codes to download. Even when the blower isn't running the display shows the fan speed at full. The blower won't work with the ec switch engaged. Before digging into the car I would like to check voltage to the controller to confirm it is getting voltage. I saw a thread from A Dalton that stated that MB put a 3 prong plug on top to make troubleshooting easy, but I can't see any plug. Is it below the fresh air filter housing? Any help is greatly appreciated. Too hot down here in Fla to be without AC and the boss ain't happy.
Pete