Hi Tim, I turned it in both directions and the fan did not stop.
Is the fan relay easy to find? or is this not really a DIY project. I am happy to hire someone, I just haven't had much luck finding an experienced trouble shooter. Does it happen to show in any of these photos?
To be sure, it's this thing right? Does it need replacing? Is there anything else I can try? Thanks for all of your help so far.
I replaced the whole fan control and the problem is now slightly different. I probably have some wires mixed up. The original fan control was a Rheem 47-19807-01, see attached pictures. When rewiring, I substituted the brown wire (new control - the Honeywell from your link above) for the yellow wire (old control). Otherwise, everything is in the same place. Now when the thermostat is set to auto (for fan control) the fan runs continuously. If I switch the thermostat to on, the fan turns off completely (won't come on even when the limit switch hits the on temperature).
Right now I can:
The fan is running on low speed, when I turn the fan "on" using the thermostat, it runs on a higher speed. Could there be something wrong on the cooling side? Here is the wiring diagram for the furnace and fan control.
This is a downdraft furnace. I pulled the fan control relay and ohmed accross the red/black normally open contacts - it does show continuity. Does that mean the TDC contacts are stuck shut? Here's a picture of what I'm guessing is the TDC:
Here's the inside. I checked the continuity inside and there is continuity from red to red and from red to black.
Thanks for all your help - this was a really great experience. It is very satisfying to have the heater back up and running without the fan going all the time. Ruud wasn't very helpful in finding this part and neither were my local part stores. Hopefully I'll be able to track it down on the web.