I've got an air handler in the attic - "hydro air" unit for heat and AC. The unit is 10 years old. Robertshaw t-stat. Air handler is "First Co.".

Currently, when I turn the blower/fan on the t-stat to "on" (even if heat/cool setting is "off" - the fan would come on but then after a few minutes would turn off. After sliding fan back to "auto" for a few minutes (may 5-10 mins) - I would try again and the blower would come back on. Sometimes it would stay on, sometimes it would turn off again.

Now on a hot day in Mass. - I've got the AC on - an basically the same thing. I put t-stat to "cool" - and with fan on "auto", I click temp down until I hear it click to call for air. The blower comes on WITH condenser running (cool air) - but only for a few minutes when the fan STOPS but CONDENSER KEEPS RUNNING (because air temp is not satisfied). If I click temp up to cease the call for air and let it stand for a few minutes, and then click back down to call for AC again, it comes back on - but again only for a few minutes (i.e., the cycle repeats in failure...)

One thing I'm not sure of - I didn't really ever test it properly: when calling for heat, does the fan also konk out before heat temp reached. I don't recall having this fan issue when using heat - but it hasn't been cold in several weeks (we haven't used the heat...)

In short - all circuits seem to be calling/responding appropriately except FAN is not staying on when needed.

Any insight greatly appreciated.

Thanks -
Brad