The furnace won't kick on when the fan set on "auto"
#1
12-26-14, 10:39 AM
The furnace won't kick on when the fan set on "auto"
The furnace won't kick on when the fan set on "auto". We'll hear a click sound seem to try to start, then it'll stop. It'll make a few tries like that. However, If we set the Fan to "On", the furnace will kick on when the room temp goes below the set temp. And it'll kick off after room temp reach the set temp, if we don't switch the fan manually to auto, the fan will keep going and blow cool air.
My question: If we just run it by manually switch Fan to "on" before we fix it, will we do any damage to the system or any safety issue?
Thanks!
Cindy
My question: If we just run it by manually switch Fan to "on" before we fix it, will we do any damage to the system or any safety issue?
Thanks!
Cindy
#2
12-26-14, 12:05 PM
No damage will done by having it in the " on" position. Go ahead and run it. Where are you hearing the click?
Last edited by skaggsje; 12-26-14 at 12:08 PM. Reason: added
#4
12-26-14, 04:38 PM
The click seems to come from the thermostat, at the same time, the unit make sounds (blowing sound?) seems try to start, but they both just last 1 or 2 seconds, and then stop. And the thermostat display will change quick from "heat on" to "- AC".
Thanks!
Cindy
Thanks!
Cindy
#5
12-26-14, 04:45 PM
Yes. It was running fine, then we had a 2, 3 mild days and it didn't come up cause the room temp was higher than our set temp. The unit is probably 15 years old. But there were years we didn't use the room much, and so we set the temp low, such as 50F or lower.
Thx!
Cindy
Thx!
Cindy
#6
12-26-14, 05:27 PM
Member
Is your thermostat powered only by batteries? If so, low batteries can cause erratic operation of the system. Is there a wire attached to the C terminal on the thermostat?
#8
12-27-14, 11:11 AM
Member
You are correct, a C wire is not connected at the thermostat. From the symptoms you describe, it sounds like a bad thermostat. The best method to test if the thermostat is the problem is to remove the thermostat from the equation. To do so, turn off power to the furnace. Remove the wires going to the R and W thermostat terminals and twist them together. Restore power to the furnace and see if the furnace will start up and operate normally for a few minutes. If the furnace operates normally it points to a bad thermostat.
#9
12-27-14, 01:24 PM
Thanks. The red wire from the wall is connected to Rc first, and looks like a short one from Rc to R. Do we remove the wire from Rc or R? Should we just turn switch on the furnace to power off or need to turn the circuit breakers off?
Thanks!
Cindy
Thanks!
Cindy
#10
12-27-14, 01:33 PM
Member
Turn the switch off at the furnace,just remove the red wire that is in the cable and splice it to the white,then turn the power back on.
Geo
Geo
#11
12-27-14, 05:21 PM
Thank you all! I did more reading online about how the furnace works. Could this be a so called "induced motor" problem? Since the blower does kick off at the right temp, does this mean the thermostat is working?
How can I test the induced motor?
How can I test the induced motor?
#12
12-27-14, 07:40 PM
Member
To better assist please post the model number of your furnace. It will be located on a data plate inside the burner compartment. The inducer motor is the first thing that should start up after the thermostat is set to heat. If the inducer motor does not start up right away the furnace should not ignite the burners.
What is the age of this furnace?
What is the age of this furnace?
#13
12-28-14, 05:23 AM
Member
If the furnace runs OK in the fan ON then it's doubtful that it's the draft inducer motor,with the thermostat set to manual and blowing cool air would be normal.did you do the test in post 10?
Geo
Geo
#15
12-28-14, 09:11 AM
just did the test in post 10. Yes, everything works fine when we twist the red line and white line dirrectly. I guess it's the thermostat. So should we just replace the whole thermostat?
Thanks!
Cindy
Thanks!
Cindy
#16
12-28-14, 09:35 AM
Member
That would be your best option,one other thing is to check the pins on the subbase to be sure they are clean and making good contact with the Tstat ,it doesn't appear you have an extra wire at your Tstat so the new one will have to be battery powered.this might be a good choice,Honeywell, 7-Day Universal Programmable Thermostat, RTH7500D at The Home Depot - Tablet
Geo
Geo
#17
12-28-14, 04:53 PM
Thanks! We are replacing the thermostat. We need to know if the system "a single stage heat and cool" or "multistage heat and cool". The model is Acroaire RPJ II, model number GNJ050N12A1. I couldn't find on acroaire's website. Any idea?
Cindy
Cindy
