Hello,

I have 3 blinking lights on a Goodman GMNT080-4B gas furnace. An online manual says this is caused by "PRESSURE SWITCH FAILURE TO CLOSE" and to check: "VENTER, PRESSURE SWITCH, VENT BLOCKAGE".

One potentially useful bit of diagnostic information is that if I suck on the hose going into the pressure switch, the status light turns solid red: "NORMAL OPERATION". It returns to three blinking light immediately after I quit applying suction.

My assumption is that the blower assembly is not producing enough suction to pull the switch closed. Is there an easy way to determine of the problem is the switch or the blower motor?

Any other advice greatly appreciated and nothing is too basic. This is my first foray into the working of the furnace.

Thank you.

Lewis

Here is a quick update on the problem we experienced. It was caused by condensation in the PVC pipe leading to the outside of the house. The pipe was not sloped sufficiently. In fact over one section it actually sloped the wrong way. As a result, condensation quickly built up in the pipe reducing airflow to the point that the furnace would not ignite. The pipe did gurgle quite a bit. Once the pipe was sloped so that the condensation drained correctly, all of our hvac trouble evaporated - no more gurgling either. It has been several weeks since that repair with no sign of trouble or any abnormal delay in ignition.

Glad you got it fixed, thanks for the update. And sorry We missed your question.