Polar 720 question...

Make sure that your excercise selected on the 720 is not set to No Bike

Press the red start button once to find heart beat, then press start button again to start recording functions.

Ian:

When I see this problem on my Polar 720I it is in all circumstances when the two little post on the handlebar mount aren't aligned with the two sensors spots on the back of the watch. Once they're lined up you should be all set.

Other then that I've found occasionally that the sensors that is connected to the lower rear derailler pully needs to be cleaned off now and then.

Cheers

Bryan

Chances that both sensors are not working/aligned would be slim. As mentioned above, make sure that your exercise set has the Bike feature on:

* Press the red button once.

* Press and hold the lower right button, it will either say "No Bike" (or something like that) or the name of the other 2 bikes. Pressing and holding again changes the setting, and it stays that way until manually changed again.

Hope that helps.

It could also be distance from the sensor to the watch, which I'm guessing is mounted on the handlebars near the stem. I had this problem with my speed constantly zeroing out and stopping the watch and a local racer who happens to work at Polar in tech support told me that my sensor was probably mounted too far down the fork. I sent it to him and he had them boost the signal (something best left to the guys at Polar I'm told). He said that this might result in slightly decreased battery life for the sensor but for me it was a worthwhile trade-off as the problem cleared up right away and never returned. For the cadence, if its mounted as far up the downtube (not the seat-tube) as possible while still connecting with the crank-arm magnet, it should be close enough, although I'd imagine they could boost the signal strength of that sensor as well if need be.
Hope this helps.