white-rodgers 1F97-371 trouble

Hello, I purchased a 1F97-371 thermostat and installed it myself according to the instruction manual. It replaced a mechanical thermostat. I have a heat only, cool only, & heat/cool single transformer system. I tested it and all functions are working properly, it heats, cools, runs the fan, etc. Over the summer, the AC worked fine
But, I seem to have some problem. Recently, the weather here has allowed me to turn off heating and cooling and I noticed something strange. One evening I heard the furnace fan engage for about 5 s, stop for 2 s, and then repeat continuously. Also, I should say the the fan doesn't operate "full blast". It sounds like it is just starting and then it shuts off.
I pulled the thermostat off the wall plate and it stopped. Put it back on and it started the fan cycling again. So I know that the thermostat is making the fan come on. The thermostat is set OFF.
So, I pulled it off the wall, pulled the batteries and let it set for 24 hrs. Thinking that this would reset it.
I put it back on the wall and, NO cycling, good.
But, about 2 weeks later, still having not used the heating or cooling, it started this cycling again. So, now I am annoyed. Clearly this is not an isolated thing.
I pulled it off the wall, pulled the batteries and let it reset again for a couple of days and now it is not cycling.
My hunch is that the cycling is the thermostat using the "phantom power" mode and this is pulling enough juice to momentarily kick the fan on. But what do I know?
Anyway, what do you suggest.
Thanks
D. Wipf
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It seems peculiar to me that the stat would be pulling in the fan, who's wire should be connected to the "G" terminal and I have no idea what thermostat this is , but make sure if it is a single transformer system, the the " R" wire is connected to to both the RC an RH terminals. Many thermostats have a charging circuit which works by "stealing" current when the thermostat is satisfied. I have found that in some ice cube relays used today, they require so little current that this charging circuit inadvertently pulls them in, generally causing "chatter in the relay. The fan relay however may have a holding circuit causing it to stay energized, then time out. If this is the case, I would either scrap the thermostat or get a larger amperage relay for the fan. How's that for a simple answer??

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Well, I didn't catch the model, serial, or even the brand furnace that the OP has installed this stat on, but I have ran into some models that need an isolation relay to prevent strange things from happening. Not to hard to correct.
Bobby

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This is Turtle.
Just install a Blocker relay on the heat mode of the 24 volt circuit and stop it. No big deal at all.
TURTLE
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Call WR they'll help you.

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This is Turtle.
He can call them but they will tell him the same thing for this bleeding over in heat mode is a common thing with digital thermostats. Now he could try another thermostat to see if he could get by with a new one but your odds are very slim to get it to not bleed over because it is a conflick between the furnace control system and the digital thermostat. I see about 3 or 4 a year like clock work.
TURTLE
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