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C-BAND satellites broadcast 24 channels with 12 transmitters by making every other channel either horizontal or vertical polarity thereby being able to put an odd an even channel on one transmitter. When your satellite receiver changes from an odd to an even channel it sends a signal to a servo motor mounted on your feed horn and tells the servo to rotate 90 degrees. The servo motor drives a 2" long satellite antenna inside the circular throat on your feed horn. This throat is where all the signals from the dish are aimed and concentrated at. When the servo motor rotates 90 degrees so does the 2" antenna and picks up the channel on the opposite polarity. The results of this circut not working on a single lnb or c/ku system is you only get odd or even channels. If you stand out at the dish and someone in the house continually changes channels you will hear the servo motor operating if it is operating.

It would be very rare if the receiver itself was the problem. Your receiver has in the set up menu a place to tell the receiver what kind of feed horn LNB set up you have. Make sure this matches your system if you have a single lnb polarotor system make sure that is what it says in this section. Next check the wiring. Some receivers have screw terminals instead of the push terminals shown here and the location of this circut on the back of your receiver can be obtained by looking in your owners manual and the back of your receiver. If the wiring and receiver set up menu settings are ok and you do not hear the servo motor running with someone else changing channels inside the chances are you need a new servo motor, which is easy to replace.

If you have a dual C-Band LNB system then there is no servo motor the receiver just switches between the horizontal and vertical LNB, check the receiver set up menu make sure your receiver polarizer set up is dual C LNB. Next switch the coax wires at the LNBs and the receiver and see if the lost polarity changes to the opposite polarity, if it does you have a problem in the coax. Next swap the LNBs on the feed horn and see if the lost polarity changes to the opposite polarity, if it does you have a bad LNB.
Receivers with only one LNB input that have dual LNBs or C/KU have an outboard LNB switching system, make sure this switching system is ok and its wires are in the right terminals if so equiped.