My solar sensor failed recently and here is what I learned. Like spishex said, the solar, water, and air temp sensors are interchangeable, but Jandy produced two different versions or generations of these sensors, so you need to get the version that is compatible with your Aqualink unit. The sensor is basically a 50-cent thermistor encased in plastic, with weatherproof leads attached. A thermistor is a resistor that provides decreasing resistance to current as temperature increases. You want a sensor/thermistor that provides the correct temperature response curve for your Aqualink. The sensors for the Aqualink RS units are the 77xx series, and provide a resistance of 19.9k to 5.3k ohms for temperatures between 50 and 104F. The sensors for the older Aqualink units provide different resistance values within this temperature range. I know that the 7790 is what I need for my Aqualink RS. The 3702 part you mentioned might be for the older Aqualink units.
I didn't have time to climb on my roof and replace my failed solar sensor, so I'm using a temporary fix for now. I went to Radio Shack and bought a 5-pack of 5.6k ohm half-watt resistors for a buck, and substituted one of those for the sensor leads at screws 3 & 4 in the the control box. I know, sounds a little like putting a penny in a fuse box but I don't think the solar sensor has a safety purpose. As far as my Aqualink knows, its always 102F on my roof.
