[BobbyC]

Ac works as it should when running in the on position but when I put it in auto it will run until it hits set temp turns off then only the box on the outside runs and freezes up the fan inside does not turn on and takes hours to turn back on when left off

 

[markusolas]

Probably thermostat is bad. Need to check with multimeter if thermostat is calling fan but start with thermostat. You can leave to on fan and it’s good too. I have rental that relay is bad and fan spinning for 8 years non stop and it not a problem

 

[BobbyC]

Probably thermostat is bad. Need to check with multimeter if thermostat is calling fan but start with thermostat. You can leave to on fan and it’s good too. I have rental that relay is bad and fan spinning for 8 years non stop and it not a problem

I was thinking the thermostat could be the problem to so I replaced it and put a new thermostat and still have the same problem what are the chances it could be the relay?

 

[markusolas]

Post pictures of your thermostat wiring and also wiring on furnace board. If bad relay then fan on would not work either.

 

[BobbyC]

 

[BobbyC]

When I opened the box I saw that fuse was blown on that red wire so I replaced it with another 3amp fuse but the fan still does not come on I don’t think the fan motor is bad it was blowing strong through all vents when it turned on now it doesn’t come on at all

 

[BobbyC]

 

[BobbyC]

Where would the fan relay be located

 

[markusolas]

Ok. So you have air handler inside and probably heat pump outside. Blue wire is common or ground so it’s not goes on B . That’s why it’s short your fuse

 

[markusolas]

Blue wire should go on C. If you don’t have it then won’t use it

 

[markusolas]

B means brown and O orange so if you have heat pump outside then you use B if it’s Rheem or Rude and O if other brands

 

[BobbyC]

 

[BobbyC]

This was the wiring on the old thermostat and I believe it’s a electric heater

 

[BobbyC]

Electric heater

 

[BobbyC]

The new thermostat does not have the C for blue wire

 

[markusolas]

Don’t use blue wire on new thermostat. That’s why your fuse is burning.Blue is ground and goes only on C if you have.

 

[eggs]

Sounds like you have a bit of a mess. The C terminal is common, that is where you had the blue wire. On the new stat, you put the blue on B, that is a heat pump command looking to send power to a relay. By putting the Blue wire on it, that was a direct short and you blew the fuse. Hopefully you did not other damage. Some thermostats can be programmed to bring fan on when you call for AC, others do not. Some furnaces energize a relay on a call for AC. With out knowing model numbers or wiring drawings, with the thousands of units out there, there is no common answer. So the C terminal is used on some thermostats which require more power to run than others. Some have batteries that power the stat that do not require the C (common). If your stat is programmable, check the manual, set fan to on when a call for AC. Good Luck, with out more info, not much else can be done.