DGAT056DBF won't turn on

[a300pks]

I have a DGAT056DBF Ser# 02427666000 1999 vintage.
In Auto Heat the problem light first comes on steady green, I hear a click and a hum then get a second click at which time the problem light begins a series of three flashes indicating "Combustion Air Switch Failed to Close". I ordered from you and replaced this switch but the problem remains the same with the new switch.
It is a combination Heat/Air Conditioning unit and works fine in Air Conditioning mode of operation.
The hoses to the Air Switch are tight and in good condition.
I would greatly appreciate and ideas on further troubleshooting of this problem.

[Robert]

Can be a damaged-loose-seperated vent pipe, booster motor not operating correctly, bad pressure switch or loose, kinked or clogged tubes.

That is usual causes for that, in order to check motor you need special tools/equipment.


You can inspect the vent pipe from booster motor.


If it is ok, would need to call a HVAC Tech for further testing of system.


Thanks,
Robert

[Robert]

One thing to add. There are two small wires connected to the pressure switch.

Using a multi-meter, test both wire connections to a good ground for 24-28VAC.


Thanks,
Robert