4 Flashes - Open High Limit

mikesal3731

Hello-
I have a Goodman GMH950453BXAE two stage gas furnace (installed 2014). It blows unheated air and the red LED light is flashing 4 times which indicates open high limit. I've tested the high and aux limit switches (tested good) also jumped both of them simultaneously and still get the 4 flashes. I checked exhaust intake and outtake and do not see any blockages. I also tested the pressure switches to make sure the circuit closes after induction starts (tested good). I've read that sometimes 4 flashes is due to a faulty circuit control board so I changed this out too!
Could it be the thermostat controller? I'm not sure what else to check before I give up and call an appliance technician.
Thanks in advance for any help.
Mike

JUGHNE

There could be about 1/2 dozen limit switches on any furnace.
I don't know anything about that furnace but have seen limits on:
the air plenum (usually auto reset), maybe 2 on burner chamber where the firing starts, on the inducer fan housing, on each side of the air blower housing, (in the event the furnace can be installed horizontally). Most of them are manual reset with a small red button between the wires.
There may be one continuous loop of wiring connecting these limits. Maybe blue in color. Usually easy to follow.
But just about never T-stat issue.

mikesal3731

Okay thanks, I'll search for more switches to check.

HVACNUT

You can try to reset the limit that opened, but unless it's something as simple as replacing a dirty air filter, its probably going to trip again. It did exactly what it was designed to do. 
If a clean air filter doesn't do it, you'll need an HVAC tech, not necessarily an appliance tech.