A/C Thermostat Malfunctioning
 

I have a two storey home with two thermostats(Honeywell) controlling
the upstairs and downstairs independently of eachother. The cooling
system is Lennox. Lately the downstairs airconditioning seems to shut
off when the upstairs is turned on and sometimes completely stops
working. Any suggestion on what needs to be done would be greatly
appreciated!
Thanks!
Michelle