Nordyne pressure switch ordeal

[splus]

I started a a/c install 3 days ago furnace is a nordyne kg7tc 2-stage that was installed 3 years ago with no issues.While do the low voltage wiring with new stat i deside to start furnace and check operation.status light is telling me pressure switch error so i take the tube off of inducer and work pressure manually through the tube and it closes i put tube on inducer furnace fires i cycle it again and it fires,today i go back to finish a/c install and i have the same issue.the furace will fire only after i blow in and out of the air tube connected to the inducer and its not the condensate switches either so what could cause this other than a replacement switch.

[rundawg]

start furnace and check operation.status light is telling me pressure switch error .

Which error - PS Closed Fault, or PS Open Fault ?

If the switch is closed because it failed to open on previous shut down, then I would say it is probably a bad switch.

If the switch failed to close after the inducer started, then it could be anyone of the following :

- Blocked Vent
- Undersized Vent
- Water in Pressure Switch Tubing
- Cracked Pressure Switch Tubing
- Inducer not Running at Full Speed
- Bad Pressure Switch
- Blocked Heat Exchanger

[beenthere]

Is moisture getting into the hose.

[splus]

I did take all the hoses off and made sure nothing was inside them,the furnace did cycle two times and then three days later i have the same pressure switch error.

[skippedover]

Answer Rundawg's question and you may get a useful reply. Is the switch failing 'open' or 'closed'?

[billygoat22]

How's the venting? if its borderline you can get intermittent shutdowns. Pressure at tap when furnace starts vs pressure switch setting?

[Thorazine]

I had one do something similar after a thunderstorm. It screwed up the circus (yes I said circus) board.