[mark e]

Have a goodman model gmpn080-4 I lost blower limit pressure switch previously and seemed to be the same thing, ordered part and still does same thing. Thought it may have had a vacuum leak so I sealed the edges, as long as it is not connected (securely) to the exhaust pipe it runs fine. As soon as I tighten down it does the thee blink sequence that says a bad switch or blockage. Has anyone seen this happen? The exhaust pipe is clear?

[therinnaiguy]

Check both the air intake as well as the exhaust. Also make sure air filter is clean and condensate is draining and all hoses are clear of debris.

[acetc]

Make sure the fittings that the pressure switch tubing are attached to are open and not clogged up. Good luck, Mike

[mark e]

Thanks for the responses, yes I have triple checked all my connections and have good air circulation. One thing I thought is the exhaust blower motor may not have enough power with the back pressure of the exhaust, and that's why it kicks the code?

[Frdbrkl]

This is a vent blockage, plain and simple. If it works fine with the exhaust removed, but fails when you connect it, there is a venting problem. You will need to make *sure* the vent is clear, and check the existing venting against the installation instructions for that model furnace. Are there long horizontal runs with "bellies" in the pipe? Is there a reducer in a horizontal run? Is there a screen on the outdoor side preventing squirrels and mice from nesting in the pipe?

You may need to get a tech to look at this-and I don't recommend you call the people that installed it. If they put it in wrong, they aren't going to be that quick to tell you.