Air handler blower doesn't work in "Auto" mode

dvsrikanth · 12-01-2010, 05:24 PM

Hi everyone. New here and hoping to get some help. The problem I am having is that sometimes in "Auto" mode, the blower fan doesn't run. Thermostat calls for heat, the furnace starts and the pipes are hot. Only thing is that the blower fan doesnt start by itself. I suspected that the problem may be with thermostat but replacing the thermostat did not help. If I turn it to the "FAN ON" position it works great but fan will not kick in automatically the "FAN AUTO" position. What should I do? The problem is intermittent and seems to happen when the attic is very cold (not fully sure if this is the cause). Please help.

The air handler is made by FirstCo and is about 10 years old.

**beenthere** · 12-01-2010, 05:45 PM

Could be a temp sensor on the coil that is not working right. Or the water not getting hot enough to make it turn the fan on.

dvsrikanth · 12-01-2010, 05:59 PM

The water is really hot. The pipes are hot and the whole attic becomes hot.

The funny thing is that every works well once I change the mode to "ON", let it run for few minutes and then put it back to "Auto". if temp sensor was the problem, will I get the above behavior?

**beenthere** · 12-01-2010, 06:14 PM

You could depending what type of sensor they are using.

dvsrikanth · 12-02-2010, 11:51 PM

The problem happened again today. Does the temperature in the attic, surrounding the air handler, affect the fan to be started in auto mode. Can this happen if capacitor is bad?

**beenthere** · 12-03-2010, 06:05 AM

The air temp of the attic can effect it depending what type of control it is.

maybe you can post the brand and model number of the control that turns the fan on and off when in heat mode.

dvsrikanth · 12-03-2010, 02:13 PM

The air handler is made by First Co

Model is 24MBXR-3HW

Fan coil Unit 27JF