Why is the black square on my digital thermostat flashing I own a dependable 92 furnace? The furnace came on briefly today It is not putting out any...

The furnace came on briefly today It is not putting out any hot nouns .Though it did for about 3 minutes a black square next to a two inside it is flashing on the digital thermostat
I am asking this cross-examine as a potentional...
Answers:    get the instruction book for you thermostat if you cannot find it google the brand and get it online
Does wet merely enter a toliet from one...
The thermostat is flashing an error code... If you own the instruction manual for the thermostat it will inform you what went wrong... If I'm not mistaking it's an error code for fiasco to ignite... But it can't be sure...