We live in an old vacation cottage with a Coleman (yep, that’s the name on the badge and the mfg plate under the cover) NG FA furnace.  It works fine for now, and yes, we do have a CO detector.

It has a bimetal strip or spring of some sort that controls the blower*.  The end of the strip has the relay actuator.  It looks like a rounded off, upside-down triangle.  The strip intersects the triangle at the bottom, the sides of the triangle touch rollers that move the relay contacts together and apart, and the top of the triangle has three tabs for adjustments. 

*I assume that this is what it is becauce of how it reacts to heat

There are three settings: Blower OFF, Blower ON, Limit OFF (Blower ON/Gas OFF).  The former two are adjustable, the latter is fixed.

Thermostat calls for heat, burner ignites, temp in heat exchanger rises, bimetal strip rotates actuator, relay closes, blower comes on, temp in house rises, thermostat cancels call for heat, burner is shut off, temp in heat exchanger falls as blower scavenges the last bit of heat, blower turns off.

It all works great except for that last item:  The blower does not turn off.  The actuator is swinging as it should.  It seems as though the last 20 years or so has worn down one of the edges and/or one of the rollers.

To turn off the blower I can give the front of the furnace a hit with the side of my fist (a la “The Fonz”) or I can open it up and touch the actuator.  It is just a gnat’s hair from turning off, but it never gets there.

Is this still a commonly available item?  Is it hard to change? Is it expensive?  I think that it is all one unit and that the actuator and strip do not come apart.  The mfg on this part of the unit is ITT.

I have considered sticking a piece of aluminum tape on that edge of the actuator or around the roller to act as a shim, but thought I’d ask here first.