Carrier furnace low heat pressure switch issue

I have a 93% energy efficient two stage carrier furnace. Its currently showing a 32 error which means low heat pressure switch is not closing or staying open. I took off all the pressure tubing and made sure it was clear and still no luck. The thermostat calls for heat, induction fan kicks on, but the glow plug never lights and the burner never kicks in. I took the tube off at the combustion chamber and I can blow in it when the furnace first starts up and it will ignite, but goes out again once the blower comes on. Any ideas?

One odd side note, the furnace has two pressure tubes, one for the pressure switch and one goes to the condensation trap. Depending on whether or not the furnace is down force or upforce depends on which one goes where. I swapped the two and the furnace works correctly, but according to the manual that setup should only he used for an updraft furnace and mine is a downdraft. Not sure if that means something in particular or not. Any help would be appreciated.

 

Having the pressure switch fail to close is caused by low airflow through the heat exchanger and venting. (combustion side> this has nothing to do with the main blower)

Causes:

1. Plugged condensate lines.

Check the trap and condensate lines for blockages, then re-prime the trap:

There a plug on the ventor motor that you remove and pour water into to prime the trap.

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Blockages in the venting:

2. Check the exhaust and intake pipes for blockages. With the furnace running, check exhaust pipe for airflow

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Plugged secondary heat exchanger or badly cracked primary heat exchanger:

3. Call a pro

 

If it were the heat exchanger though would the furnace still work when the pressure tubing is setup in the upflow configuration? When I do that it works perfectly, its only once I swap the two pressure tubes around for a downflow configuration that it stops working.

 

Ended up getting it working. Noticed I couldn't blow or suck any air through the pressure tube connected to the low heat pressure switch. Followed the tube from the pressure switch back to where it plugs into the induction housing unit. Unplugged the tube from the induction housing unit and looked in the valve with a flashlight and noticed a buildup of gray material. Used a paperclip to clear it out and was then able to draw air through the tube. Hooked the tube back up the the induction housing unit and to the pressure switch and its working like a champ. Thanks everyone for your input!

 

Thanks for the follow up.