Air Conditioning - Blower only works when manually turned on

Our unit is a Sears Pilot Free Gas Fired Counterflow Furnace with air conditioning. We have lived in this house for 12 years and the unit was here when we moved in. The problem that we are having is that when in auto mode, the outside unit comes on but the blower does not. It will not come on when turned to on at the thermostat but there is a manual switch on the inside unit and when turned on, the blower comes on. We have replaced the thermostat and had began to think that the relay was bad. We had the heat and air guy test the relay and he said it is fine, HOWEVER, when in auto mode, if we push on the relay, the blower will come on. Sometimes it will work fine for a day, sometimes for only a few minutes. We have checked the wires on the board and cannot find any loose or torn wires, and the relay doesn't seem to be loose, but why does it kick the blower on when we push on it? We are out of ideas :wall: .
Also, while doing research on parts and assembly, we discovered that the inside unit is supposed to have 2 filters in it: it has NONE, :eek:! Could this be the cause of our problem or is this going to be the cause of future problems?
Any help would be much appreciated.
Thanks in advance!

Are you getting 24 volts at the relay? if not, trace back till you get a reading.. there may be a break in the wire that you won't see.

if there no filter, do you have a fitler at the return grill?? If you have a filter in the grill, then that's all you need.. but you don't have one in the return.. Then I'd say it's time to take the unit apart and give a good cleaning.. Maybe best to get the Pro in to do it.