Blower and recirculator fan keep running when thermostat is off

[nbareket]

Furnace is Rheem RGLG.  Only way to stop these fans from running is unplugging the power. No ignition.   Limit switches seem to be ok  (tested by shorting the wires).  Controller green lights come up normally.  What should I check next? 

[jb8103]

Without looking at any data sheet or diagram I'd say you've got a stuck relay; let me see what info I can find on this. Got a model number?

[jb8103]

Here's some stuff:

 

http://www.mediafire.com/view/?ri27ksov238adu5

 

I just took the purple pill so I won't be with you for long...it's laying down...like I will be shortly...if this has the abominable fan control center stuck on top of the transformer you're in for a world of weird...

Edited January 19, 2014 by jb8103

[jb8103]

OK, study the manual you've downloaded and determine if you have a standing pilot type, or one of the ignition controller types. Whichever, you'll be replacing boards or controllers.

You're all drifting so far away...and sort of dreamy looking...good night all...

[nbareket]

I have a circuit board controller.

 

A stuck relay is probably the best theory...  I will replace the circuit board and hopefully problem solved.

[Budget Appliance Repair]

Did you make sure the "Fan/Auto-ON" switch hasn't gotten changed to the ON setting.

 

If the green wire is connected into the wall t-stat the "Fan/Auto-ON" switch should be

switched to the AUTO setting, (unless you want the blower to run continuously for

some reason).

 

If the setting is correct you might want to pull the cover off the t-stat and see if you have

a green, red and white wire attached and disconnect the green.  If the fan stops running

with the heat switch in off and the green wire removed then there is a problem with the

t-stat keeping the fan blower on.

[ACtechGUY]

What you describe is an open Hi  temp limit . The logic built into the control board sees one of the limits open and will run the main blower( big fan) and the draft inducer fan motor assuming that the heater is hotter than it should be . it runns the fans to try to cool down the furnace.

 

  You will either have one or two high limits and one or more rollout switches .  If any of these limits  are  open the blowers will run constantly . check  all limits for continutiy.  Rheems with the original control board are kinda stupid about not giving a trouble flash for an open limit. 

 

Its also very possible that the control board is bad as well . I have seen this exact thing with a bad board.

 

Does the furnace fire with a call for heat? if so it cannot be a bad limit, and is more likely a failing board.  

[nbareket]

Found the problem!  Two limit switches went bad at the same time.  Weird.  Anyway, thanks all for the good suggestions.