2001 Chevy Impala Strange Problem

Other Category problem
2001 Chevy Impala 6 cyl Wheel Drive Type unknown Automatic 118K miles

Hi,
I've been having issue with my 2001 Impala since the summer and have yet to find out what is wrong. It started off with a low coolant light going on and the coolant level was good, by the end of the summer my ac would sometime work sometime no. My gas gauge also would read full then a few minutes later 1/4 tank than full again. It is now winter and the fan for the heat will not come on. If I banged under the dash on the left side it used to get the fan working but this is no longer working. ALso the little message thing (sorry) that tells the outside temp, mpg ect seems to go out the same time as the heat, fan ect. I have had it hooked up to a code reader and nothing. I have very little cash to have fixed and can't get a new car so. Any help you can provide that may save me a few dollors trying to figure the problem out would be great. Once in a while after driving for a while the heat will come back on this this is not very often. I drive 1 hour to work and today it was 28 outside. Thanks for your help