The climate control on my 87 300e is acting strange. Most of the time it works great. Occasionaly when in the normal heating mode the air will stop blowing from the floor vent and continue from the outside dash vent. When this happens the air gets extremely hot. Also, when the off button is pushed the blower continues to blow hot air. Pushing any of the climate control buttons has no effect. When I stop the car and turn off the ignition re-start everything works fine. It is though something resets when the car is restarted. Naturally when I take the car to my tech it never happens. I have replaced the fuse in the fuse box and also the 30amp strip fuse outside of the fuse box. Is there some type of relay, sensor or vacumn to check? Is it the climate control unit? What else can I check?

Thanks in advance.