My robertshaw non programmable wall thermostat doesn't want to work when I press the temp up or down buttons, eventually they work but I have to press button many, many times, could it be the contacts/points need cleaning, I don't even know how to take the cover off the thermostat, can you please tell me what to try, it's a item 9420 home wall mount unit. THANK YOU

Sounds like the thermostat is simply worn out. Most new stats are fairly cheap (less than fifty bucks) so I would suggest replacing the stat. If you have push button control, there is no cleaning the contacts. Simple replacement of stat is the only real fix here. I suggest getting a stat manufactured by Honeywell, as they are the leader in thermostats and will have the most options, as well as warranty.