[Bmp903]

Having limit circuit issues on Goodman furnace. I have replaced both limit switches and both rollout switches. I get the 4 flashes before the furnace even lights, so it is next to impossible for it to be actually a limit circuit issue unless I am missing something. Filter is clean. Heat exchanger seems fine from match test (if furnace doesnt light in the first place I'm not sure how it could overheat anyway). I am at a loss here! Continuity checks are fine on limit and rollout switches. Pressure switch has also been replaced. With the 4 flashes coming on before the furnace even attempts to ignite, I'm leaning towards the circuit board. Any ideas

 

[user_12345a]

Ohm out all the limit circuits from the board connectors, if they're closed yet it's giving an error right away it's the board or the connection to the board.

 

[user_12345a]

...make sure it's actually a limit error and not pressure switch or flame sense.

 

[beenthere]

Does that include the limit on the blower housing?

 

[Bmp903]

I replaced the pressure switch a couple of months ago. According to manufacturere, 3 flashes indicates open pressure switch. I'm getting 4 flashes. I will check again to verify.

 

[Bmp903]

I replaced both limit switches. The one at the fire box and the one near the blower. Ohms reading for switches are around 1 to 1.5. I have not checked the wires for continuity, but will try that also! Thanks for the help.

 

[Bmp903]

Flame sensor ohms are around 1 to 1.5 also.

 

[coolair111]

Pressure switch also has a manual with it do consult it and find what 4 lights indicate.