Excerpt from my AC Problem-Solving eBook:   

Shut off the power and remove the air filter. A clogged filter is a common problem. I can’t tell you how many times I went on a service call and a customer had to pay me the hourly rate plus travel time to replace a $5.00 air filter! Your filter should be changed every 8 to 12 weeks depending on how much use you get out of your equipment (heat or AC or both). Remember, a dirty filter lowers your unit’s efficiency! I suggest using a pleated filter. They cost a little bit more but are well worth it. The washable filters I do not recommend and any filter you can see through is not a good filter. A pleated filter is more efficient and will keep your equipment much, much cleaner! 

Most refrigeration problems are electrical related or refrigerant leaks. If the fan and compressor are running you are probably low on refrigerant. Only a qualified refrigeration technician can tell if a system is truly low on gas. A system doesn't need gas after installation unless there is a leak in the system. Call your local repair man. 
 

Excerpt from my Heating Problem-Solving eBook:

Some units with electronic ignition have a glow coil which gets red hot or a zapper-like electrode. Both have the same purpose. They light the pilot, then the main burner lights. After that the blower should start. This is controlled by what is called the ignition module or a circuit board. A glow coil simply has two wires coming from it's ceramic base and requires 110 or 230 volts to make it glow...simple. 

Spark ignition is a little tricky sometimes to troubleshoot. You may need a technician. Look for broken or loose wires. Sometimes it's something obvious that is the problem. If everything looks normal but you don't get a zap (spark), shut off the power for a moment and turn the power back on. This will reset the module if it is locked out. Some modules will lock out if it tries to light the pilot but doesn't light successfully after a number of times. 

I have seen a module lock out because the pilot was dirty or a poor ground connection on the module exists or the connections are dirty. A dirty pilot can make the pilot flame weak and the sensor won't feel the heat from it. I have seen spider webs cause this problem!