I have a forced air, natural gas heater, outside A/C compressor. The brand is American Standard and its approx. 30 years old.

The symptoms started late last summer when the blower would run constantly, and the outside unit would cycle on/off normally (depending on the temp in the house). If I tapped on the fan control unit when the blower should be off (house is cold) then it turned off normally. This went on for a while and when winter came around the blower behaved itself again.

When summer came back around this year the blower again started to stay on regardless of the state of the outside unit. Again, I could tap on the fan control box and it would turn off. I determined that the control unit (Honeywell R8325A1008) was bad and replaced it with a Honeywell R8285A.

Now, everything seems to be working properly except the blower, which seems to be exactly backwards. If I set the thermostat to cool and turn it way down, the outside unit kicks on and the blower kicks off. If I set it to cool and turn it way up, the outside unit turns off and the blower comes on. If I set it to heat and turn it way up, the burner turns on and the blower turns off, and vise-versa. This is all with the fan control set to Auto. If I turn the fan control to On the fan stays on regardless of the temp setting.

What is going on here? I triple checked the wiring. Made sure it matched the old unit and even made sure it matched the published standards (R, G, Y, W, C). It looks like something is hooked up backwards but I can't seem to find it. If I remove the thermostat wires completely the blower stays on.

My next step might be to replace the thermostat or call an HVAC professional. Any thoughts you might have on what the problem might be would be great.

Thanks!
Richard

I think that you have a fan relay and it is easy to get two wires in the wong place. Look on the relay right by the terminals, see if you see numbers from one through six. And by then numbers you will see some that say N/O and N/C. The N/O stands for normally open, the N/C for normally closed. That means that N/O is open until the relay coil is energized and the N/C is closed until the coil is energized.

So see if this may be your problem.

The fan was not having this problem and the only thing I changed was the control unit. The control unit does have a relay but there are no numbered contacts (at least ones with wires). Is this the relay you are speaking of? I looked all around and could not find another relay on the unit.

Another thing I tried was to remove all the thermostat connections; the blower stayed on. Is that normal?