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airheatman, HVAC Technician
Category: HVAC
Satisfied Customers: 8384
Experience:  Furnace, A/C and heat pump specialist.
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Rheem gas furnace blower stays on after temp is reached,

Customer Question

Rheem gas furnace blower stays on after temp is reached, blows out cool air, turn up thermostat, igniter does not kick in. is that a motherboard or ignitor problem?
Submitted: 1 year ago.
Category: HVAC
Expert:  airheatman replied 1 year ago.

Look on control board and tell me if you have a green light blinking and if so how many flashes between pausing?

Customer: replied 1 year ago.
There's 3 lights on motherboard, the right and middle is green, the left is flashing yellow
Expert:  airheatman replied 1 year ago.

OK here is what the lights mean.

First green-power to unit

Second green -Error (flashes a certain number depending on error)

Yellow-FLAME. This would should only be on when burners are on.If it flickers or blinks that implies marginal flame is being sensed.

Since the yellow is blinking, lets start by cleaning the flame sensor with a dollar bill or fine sand cloth,

I will attach a pic and a link to a sample video of how to do this.The flame sensor will b in front of farthest burner from igniter and have a single orange wire attached.

Expert:  airheatman replied 1 year ago.

Now video will not be exactly like your furnace but will give you the idea

Customer: replied 1 year ago.
not helpful, ignitor still does not come on. my question was, is it the circuit board or ignitor?
Expert:  airheatman replied 1 year ago.

First of all, if you have got an error code, the blower is going to stay on and igniter will not light until you correct the problem or turn power off and back on to unit.In original question you stated igniter came on , burners and burners lit.That implies ignitor is ok. Lets do this.Clean that flame sensor, Turn power off to furnace then back on.That will reset board.Then lets see if furnace will operate correctly.