Carrier furnce, when i set thermostat to fan on, blower won't come on, but when i run the heat the fan will come on like it is suppose to,anyone have any suggestions. Thanks

Several possibilities like a failed switch on the stat or more likely a bad control board in the furnace. Does your control panel inside the furnace have any small red or orange lights blinking? This would be a failure code. Open the panel or look for a small peep hole to see the lights

No lights, i did put in a new honeywell thermostat, maybe i have it wired wrong.

Your fan relay is bad. It is cheap to fix, but make sure your coils and the fan blower wheel are clean, too. You can get a new fan relay for $5-10. Make sure you wire it correctly or you will burn up the fan motor. DrTom4444

Thank you, dr. tom4444, also, my ac won't turn on, any suggestions where to start. Thanks.

If i jump r -power to g - fan on circuit board the fan blower works, the fan runs continually, once i remove the jumper connection it shuts off, but if i move the green fan control wire to gh, another spot that's empty on the circuit board the fan works, would it be okay to leave it there or will this cause other problems? Thank you.

If you can jump it like that it is a problem in the t-stat. It won't hurt anything to leave this on. If the AC will not work either then there is a problem in the t-stat, most likely. You need to turn on the AC and see if you have a voltage reading of 24-30 volts between R and Y. If so, then the problem is in the t-stat. If there is no voltage and you have 24 volts at Common and Y then the problem is in the contactor or a safety switch is tripped or there may be no power at the outside unit. You just have to let the meter be your eyes. DrTom4444

Thank you drtom4444, with the power on to the ac nothing happens, it doesn't turn on, but when i hold down the contactor it runs and cold air comes out of the ducts, does that mean the contactor is bad or a problem with the thermostat or could it be something else? Also, while i'm at it i figure i should change the capacitors and fan relay, the motor run capacitor is not looking to good and they don't seem to be that expensive, what is your opinion on that. Also i am going to clean the evaporator coil, but i have the old uncased type made of a sheet metal box housing, i have access on three sides, any idea what is the best place to cut out an opening, i know the newer ones give you access in the front, so any feed back would be helpful, thanks again and looking forward to your commentary.

One rule is that you do nothing unless the meter says you need to do it, with a few exceptions. Is the contactor getting 24 volts? If so and it will not pull in then you have a bad coil and you need a new contactor. On the coil you should cut out the side where the pipes go in and slide out the coil. To do it right you should pump down the unit which means to close the high side valve at outside unit and run unit to pump gas into condensing unit. Most gas should be put into a recovery can first. Then when pressure is zero cut lines and take out coils and seal them up well. You need ox-acetylene torches to do this. You then use alkaline coil cleaner (liquid lye) to clean coils along with a 1500 psi pressure washer. Hope this helps. DrTom4444

I had a similar issue. For my unit the only thing not connected at all was the G to G connection from the Unit to the Thermostat

The "G" wire from the thermostat to the unit is the fan relay wire. On the coil for the fan relay you have common and "G." "R" and Common leave the 24 volt transformer secondary. "R" supplies the side of power that is switched in the thermostat. Common goes to the one side of the fan relay, the condensing unit contactor, and the reversing valve that is not switched by the thermostat; however, sometimes common is run through safeties so that when a safety trips it will drop out everything.