Thank you for replies. Steve, thanks for advise.
Well, I don't have a multimeter nor do I know how to use one.My problem is I don't know which component is causing the fan to cut out in manual mode after 40 seconds. The fact is I can't even get the fan to start in manual mode unless I first turn on the A/C. I took out the climate control unit and inspected the push button unit and the circuit board. I noticed that the circuit board was soiled with a black soot which was caked on the green side of the board. Also, a copper circuit was exposed where the green covering had melted or somehow moved to expose the circuit. I checked the sensor under the hood near the fuse box. It seemed ok. Also, I checked the sensor under the glove box. The fuse attached to it was fine. My question is, how do I figure out what to replace?