"Tony Hwang" wrote

Hi,
Blower control lead from 'stat is same for heat or cool.


Not necessarily. There's not nearly enough information here to make that
call. Many furnaces use the thermostat and subbase to "call" the blower in
AC mode, yet the blower is called directly by bonnet temperature in heating
mode.



First you have to see if G lead from 'stat is enabled when it acts up. From
there you move to control board inside furnace. You didn't mention what
kinda furnace. Any way in cool mode blower runs at higher speed.

You don't know that it has a board, or thet it runs at a different speed for
AC either. It may be just a fan center relay. Can't really tell without
more information.
I could make many guesses, such as motor, cap, wiring issue, board, fan
center, weak disconnect, etc. etc., but they would be just that, guesses.


He should probably call a guy in to look at it, unless he wants to just
follow his own steps 1) through 4). :-)

Sorry, Lefty