单项选择题

Troubleshooting Guide
When it comes to figuring out what is wrong with an air conditioning unit, most people would prefer to leave it to a licensed professional. However, it is quite possible to repair simple problems by yourself.
1. The main problem usually occurs with the filter just inside the air conditioning unit panel. Most people can change the filter themselves, but they neglect changing their air conditioning filter once a month and it ends up clogging. Be sure to change your filter and try turning the unit off for a few hours to allow any ice to thaw.
2. In addition, a low freon pressure could also be the culprit. The ideal pressure reading should be around 65-70 psi, so you will need freon gauges to get a reading from the high side (the larger of the two freon lines). Freon can slowly escape from the outside unit over time. That is why the unit must be serviced occasionally.
3. When the thermostat is turned down low and the unit inside is not coming on at all, it could be caused by the condenser fan motor. Wire connections could be burning up or may have been loosened by vibration. When this happens, it needs to be replaced.

In the e-mail, what is indicated about the air conditioning system