Having problems with your Air Conditioners ?

Fan will come on for heat(auto), but not for AC or set to ON

\015 Had to replace blower motor in October. Now that it is starting to get warmer I tried to run th AC. The blower fan will not come on. If I run the heater set to auto, it will work. If I turn the fan setting to ON or try to run the AC it will not. Outside unit runs fine.\015

Answers :

You have a blower relay in the furnace that's probably bad. In the heat mode the blower is on a temperature relay, in cooling mode the blower has to come on immediately so there is another relay for cooling. The green wire on the thermostat feeds that relay, so if you go to the furnace and shut the power off and find the green wire from the thermostat that feeds that relay and replace it, being careful to mark all the wires before removing them, also the relay terminals have numbers for identification.
You are not wired correctly at the fan limit switch. or the fan delay relay is bad. Find the fan relay, with the unit set to run and turned on, check for 24 volts on the fan relay from the t-stat.(should be a green wire going to it. No 24v repair or replace the t-stat wires or the t-stat.
\015\012If 24 v goes to the relay and it does not engage to let high voltage through, replace the fan relay.

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