Weird thermostat situation

[Anthona]

Lately, at various times, I would have to get up early in the morning, to manipulate my thermostat, because the heat did not come on at prescribed time...4:45am. the battery is not dead, there is no icon indicating such. The times are correct..so I thought it cannot be the batteries..2 AA type. I would clik on the up temperature button to hear the click of the furnace coming on and then it runs smoothly. This did not happen daily, only other day or so. Plumber said i have to replace a section on the furnace for $200 dollars. Then I called the thermostat company its the TX500 programmable unit. The tech suggested that I replace the batteries, even if there is no indication of weakness. I did, and it so far has set up the furnace to come on as prescribed. Now, although the old batteries were setting the times right and the temperatures, why should it effect the so called 'switch' of the burner to come on when its suppose to?

[Tony Hwang]

Hi, When battery is on the marginal state it will acts erratic. Maintaining clock needs minimal current but to activate discrete logicl it needs lot more current. Actually battery supplies current to the control loogic which triggers relays for furnace control. I'd do the same thing if I were you in this case, just replace battery first and see. Did not measure the battery voltages? I just replace them at about 1 year interval even tho manual says it can work a few more days when battery low indicator comes on. Digital controlled circuits are nothing but sequencial logic. Just think logical.

[Pat]

Could be weak battery, or could be a 7 day programmable thermostat and it has it's weekends mixed up if you have the date wrong.

[Anthona]

Well, my hopes were shattered. It did not come on this morning and again I had to manipulate the thermostat. and this is with new batteries. Now, either the plumber was right or I need to replace the thermostat, which is barely 2 years old. I guess replacement is cheaper than the plumbing job.

[aenewhouse]

I'd try replacing your thermostat with a nicer one before starting in on the furnace. I have a cheap "Lux" brand thermostat, and twice or three times over the past year it's randomly not turned the heat on for me. If I click it up and down once, it works fine. I've heard Honeywell is a good brand - a $70-100 thermostat sounds cheaper than furnace repairs. If you wanted to check, you could put in an old-fashioned standard thermostat for a few days, and if that works, you know it's not the furnace. Good luck, Andy

[Tekkie®]

Anthona posted for all of us...

Asked and answered MANY times - do your own research.