My goodman model #gmp075-3 has a trouble code . 3 flashes from led on circuit board. I replaced pressur sw.# b13701-33. The problem still exist. I blew through the rubber hose.no blockage. What else can I do?

It could also be the ventor or the exhaust going to the outside could be blocked.

Here is your complete service manual. This manual covers more than one model number SO make sure you use the sections for your unit!

http://www.hvacpartsshop.com/Gmph075-4%20Series.Pdf (http://www.hvacpartsshop.com/Gmph075-4%20Series.Pdf)