Hi... In August, I bought a new honeywell vision pro 8000 thermostat. I works extremely well for air conditioning. Not a problem there, but now we are into the heating, and I find, although this does not occur on a regular basis, when the heat comes on, the furnace fan will sometimes continue to run. Bugs me quite a bit as I have to go to this new thermoset and toggle back and forth between the "FAN" "on"/"auto" switch to turn off the fan. As I have said, it only does it once and a while. Most times the fan shuts off just fine... but seems to happen at morning warm up, or returning warm up... I have checked my wiring.. all seems fine there.. I took the thermostat back to Home Depote and they exchanged for a new one.. still doing this on the new one. I do have the thermostat in the "Auto" Fan mode... sometimes this also does this when my wife gets cold and puts the temp from 68 to 70... when she does this.. the furnace fan has a tendency to stay on, but will go off If I walk her through the motions of the toggle between on and auto.. if you do that the fan will shut off and work normally in the auto mode.. so I am perplexed... I even called HoneyWell... they say that there are some complaints of this problem, but I was at work and did not have the model number or serial number with me.. They told me to call back when I was at home and they could help to "try" to rectify the problem I may be having.. if this did not work, then it could be the fan relay or the limiter. I think this thermostat is great, but ticks me off when it does this.. anyone have any suggestions or have had similar problems and were able to get corrected... I have a York Stellar Plus gas forced air furnace install in 1990.. about 16 years old.. never had a problem with it.. been a great furnace... 95%+ efficiency... Any advice will be taken with appreciation... thanks.. regards.. sir sam.. :-)

I don't have the 8000 book here in front of me, but there is a fan cycle you can program or even disable. The fan on a heat cycle is controlled by the furnace. Disconnect the green wire at the stat for a few days while you are using the heat. If the fan continues to do it, it is NOT the stat's fault. So far my customers and I have loved the 8000 no complaints (how rare is that?) and no call backs.

Hi... Thanks for your help. I do have the green wire on the stat. It runs the fan for the "auto/on" toggle. I did not know that there was a fan control in the heat mode. I am suspicious that it could be my fan relay switch or the limit control. Funny how it does it... it is like a "blue moon" once in a while it will just stay on after the heating has run its function... then most times the fan just shuts off normally on cycle... but you say to remove the green wire for a couple of days? This will still give me furnace forced heat, but not let me turn the fan on or off at the auto control... I think I get it... I have also put in a work order with Direct Energy to have them come out and check the relay and limit switch.. I know about these things but not great at fixing them... anyway.. thanks.. I will give that a try... take care.. have a good one :-)

Hi again.. also found out I have the RTH 8500 model... and I cannot find that fan cycle in the heat mode... maybe there is a difference... but will keep at it... thanks... :)

My guess it is the fan relay. Likely it will get worse until it stays stuck. Maybe the work order is a good idea. You need a lot of confidence in your diagnosis before you shell out for a board.

Hi Labman... thanks for the help... I agree with you :-). I think it is the relay too... I pay for the heating plan with direct energy, so should be somewhat covered for parts and labour and not cost me an arm and a leg :).. take care and I will try to let you know how I make out with this problem... have a good one... Sir Sam.

Hi again..also found out I have the RTH 8500 model...and I cannot find that fan cycle in the heat mode...maybe there is a difference.....but will keep at it...thanks... :)
It is not just for the heat mode. It is a separate function so you can run the fan several programmed hours per day for better filtration, circulation etc. It sends a signal on green to the fan relay. The blower is turned on and off by the furnace heat cycle, there are many ways a furnace will do this, timed or by heat.

Thanks for the reply NorthernHeat. If I have this function in my Honeywell vision pro ETH "8500" how do I find it? It does not seem to state this in my manual... I have tried, but cannot find this function... do you have a way to show me... thanks.. sir sam..

Thanks for the reply NorthernHeat. If I have this function in my Honeywell vision pro ETH "8500" how do I find it? It does not seem to state this in my manual...I have tried, but cannot find this function...do you have a way to show me...thanks..sir sam..


I'll try to remember to bring a manual home with me tomarrow. But I really don't think that is the problem. Like I said disconnect the G wire at the thermostat, if fan is still wacky problem is with the furnace not the stat.